Temporal Trends of Sources of Cigarettes Among US High School Students: 2001–2015

Temporal Trends of Sources of Cigarettes Among US High School Students: 2001–2015 Abstract Introduction Restricting the supply of cigarettes to youth plays an important role in reducing youth smoking. Methods The study included data from 8 years of the national Youth Risk Behavior Survey (YRBS) from 2001 to 2015 with 99572 high school students less than 18 years old. Data were weighted to provide national estimates of the temporal trends of cigarette sources. Each cigarette source was analyzed by a separate multivariable logistic regression model and the linear trend odds ratio (aOR) was adjusted by age, sex, race/ethnicity, and smoking frequency. Results The current smoking prevalence among US high school students less than 18 years of age declined from 26.9% in 2001 to 9.9% in 2015. Among current smokers, we found an overall downward trend of buying cigarettes in a store (aOR = 0.98, confidence interval [CI] = [0.96–1.00]) and an overall upward trend of getting them “some other way” (aOR = 1.03, CI = [1.01–1.05]). The prevalence of purchasing cigarettes in a store significantly declined among smokers aged 16–17, male smokers, white smokers, and daily smokers, but not among other categories. The prevalence of getting cigarettes “some other way” significantly increased across all groups except Hispanic smokers and medium-level or daily smokers. Conclusions The proportion of high school students reporting that they bought cigarettes from a store has been declining over the years, while the proportion of high schoolers reporting that they got cigarettes “some other way” has been increasing. The temporal trends also varied by age, sex, race/ethnicity, and smoking frequency. Implications Patterns of high school student access to cigarettes have changed from 2001 to 2015, with access from “some other way” becoming more prevalent. The differences in cigarette acquisition by age, sex, race/ethnicity, and smoking frequency highlight the importance of implementing tailored policies and interventions to reduce youth access to cigarettes and prevent youth from smoking. Introduction Cigarette smoking is the leading cause of preventable death in most countries. In the United States, smoking is responsible for more than 480000 deaths and $289 billion in direct health care expenditures and lost productivity each year.1–3 Youth are at the greatest risk of smoking, as evidenced by 9 out of 10 smokers having tried their first cigarette by age 18.4 Though the cigarette smoking prevalence among youth has been declining in recent years,3,5 9.3% of high school students reported smoking cigarettes in the past 30 days, and 2.3% of middle school students reported currently smoking cigarettes in 2015.6 It is estimated that 5.6 million youth currently aged 0–17 will die early from a cigarette smoking-related illness unless youth smoking rates drop rapidly.3 An important component in reducing youth smoking is to restrict the supply of cigarettes to youth. Control of youth access to cigarettes has been included in the Best Practices for Comprehensive Tobacco Control Programs from the Centers for Disease Control and Prevention7 as well as Healthy People 2020.8 The sources of cigarettes among youth can be grouped into 2 general categories: commercial sources (buying from a store or on the Internet) and social sources (borrowing, buying, or taking from others). Though federal laws restrict the sales of cigarettes to youth under 18 years old, past studies have raised concerns about the effectiveness of such regulation.9,10 More than 60% of responders from the 2014 National Youth Tobacco Survey11 think it is “easy” or “somewhat easy” for youth to buy tobacco products in stores. In addition, youth are acquiring cigarettes from social sources, such as friends or family members. Past studies have shown that younger adolescents (vs. older youth) and nondaily smokers (vs. daily smokers) were more likely to obtain their cigarettes from social sources.12–15 Examining each of these sources of youth cigarette acquisition—social and commercial—is important to further reduce youth smoking. Given the changes in tobacco control policies, such as increased cigarette prices and enforcement of retail compliance with underage sales laws, it is reasonable to expect that youth might shift their sources of cigarette acquisition over time. A few studies examined the temporal trend of youth access to cigarettes and identified shifts in sources of where youth obtained their cigarettes.13,14 Jones et al.13 analyzed the 1995, 1997, and 1999 national Youth Risk Behavior Surveys and found that relying on store purchases significantly decreased from 38.7% in 1995 to 23.5% in 1999, while giving someone else money to buy cigarettes significantly increased. Lenk et al.14 studied trends in sources of cigarettes among adolescents from 2000 to 2006 in Minnesota and identified a downward trend of youth buying cigarettes from stores but an upward trend in stealing cigarettes from others. However, these studies either relied on data before 200013 or focused on a regional trend.14 To the best of our knowledge, no recent study has examined the temporal trends of youth access to cigarettes at the national level and assessed heterogeneity in the ways youth obtain cigarettes, such as variations by demographic status and smoking frequency. To fill the gaps in knowledge, we used a national survey from 2001 to 2015 to analyze the temporal trends of youth access to cigarettes, overall and stratified by smoking frequency and demographic characteristics. This study provides policy makers and school administrators with information and analysis to assist them in formulating strategies to control the supply of cigarettes to youth more effectively and further prevent youth from smoking. Data and Methods Data The data were collected from the national Youth Risk Behavior Survey (YRBS). The YRBS has been conducted biennially in odd-numbered years since 1991 using a nationally representative sample of high school students in grades 9–12 in the United States. The national YRBS uses a three-stage, cluster sample design. A detailed description of YRBS survey design and data collection can be found on the YRBS website.16–18 The study included data from 8 years of the YRBS from 2001 to 2015 with a total of 117815 respondents. The overall response rates (the product of the school response rate and the student response rate) varied from 60% (2015) to 71% (2009 and 2011), with a median of 68%. Since the minimum age to purchase cigarettes was 18 in most states from 2001 to 2015, students who identified themselves as ≥18 years old were excluded from this study (n = 18388). A total of 99572 respondents aged under 18 years from eight surveys (the 2001–2015 YRBS) were included in the analysis. Measures Youth Access to Cigarettes Youth access to cigarettes was based on the response to the question, “During the past 30 days, how did you usually get your own cigarettes? (Select only one response.)” The response options included “A. I did not smoke cigarettes during the past 30 days,” “B. I bought them in a store such as a convenience store, supermarket, discount store, or gas station,” “C. I bought them from a vending machine,” “D. I gave someone else money to buy them for me,” “E. I borrowed (bummed) them from someone else,” “F. A person 18 years old or older gave them to me,” “G. I took them from a store or family member,” “H. I got them some other way.” This question was first asked in the 1995 YRBS, but the response options were provided differently in the 1995–1999 surveys, and thus the 3 surveys from this period were not included in this study. In 2015, the response option C was changed to “C. I got them on the Internet.” Due to the change of this response option and small sample sizes, we did not report the response option C in this study. Current Smokers and Smoking Frequency Current smokers were defined as those who reported smoking >0 days in the past 30 days13 in response to the item, “During the past 30 days, on how many days did you smoke cigarettes?” Response options included “0 days,” “1 or 2 days,” “3 to 5 days,” “6 to 9 days,” “10 to 19 days,” “20 to 29 days,” and “all 30 days.” Based on the frequency of smoking, we further classified current smokers into 3 groups: low (1–5 days), medium (6–29 days), and daily smokers (30 days). Covariates To control for other influences, several covariates were included in the analysis, including sex (male or female), race/ethnicity (non-Hispanic (NH) white, NH-black, Hispanic, NH-American Indian or Alaska Native (AI/AN), NH-Asian, NH-Native Hawaiian or Other Pacific Islander (NH/PI), NH-others), and age (≤15 years old or 16–17 years old). Method Data were weighted to provide national estimates by accounting for the oversampling of black and Hispanic students and for nonresponse. First, weighted % and 95% confidence interval (CI) of demographic characteristics, smoking prevalence, and sources of cigarettes among high school students were reported from 2001 to 2015. Temporal trends were examined based on univariate logistic regression analyses where survey years served as a continuous variable. Second, separate multivariable logistic regression models were used to examine temporal trends of smokers obtaining their cigarettes from each source. Trend odds ratio (aOR) and 95% CI for cigarette sources, adjusted by age, sex, race/ethnicity, and smoking frequency, were reported in the multivariable analysis. Third, stratified analyses were further performed to evaluate temporal trends of each cigarette source by age, sex, race/ethnicity, and smoking frequency. Data were analyzed using SAS 9.4 (Cary, NC) survey procedures to account for the nested design of YRBS and weighting.19 A p-value <.05 was considered statistically significant. Results As shown in Table 1, the current smoking prevalence among US high school students less than 18 years old declined from 26.9% in 2001 to 9.9% in 2015 (p < .01). The distributions of respondents’ age and sex were relatively stable from 2001 to 2015, while fewer white students (from 67.1% in 2001 to 54.0% in 2015, p < .01) and more Hispanic students (from 12.1% in 2001 to 22.5% in 2015, p < .01) were included in the surveys. The prevalence of current smokers declined from 9.4% to 5.2% for smokers at the low level (p < .01), from 8.5% to 2.8% for smokers at the medium level (p < .01), and 9.0% to 1.9% for daily smokers (p < .01). Among current smokers, the proportion of high school students getting their cigarettes from different sources along with their p-values from univariate trend analysis was also presented in Table 1. Table 1. Sample Characteristics by Survey Year Among High School Students Aged <18 Years Old, YRBS 2001–2015   2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01    2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01  NH, non-Hispanic; AI/AN, American Indian or Alaska Native; NH/PI, Native Hawaiian or Other Pacific Islander; NS, not significant. ap Value for trend is based on univariate logistic regression model where survey years served as a continuous variable. bStudents who reported smoking >0 days in the past 30 days. cThe sum is not equal to 100% since the response options from “I bought them from a vending machine” in 2001–2013 and “I got them on the Internet” in 2015 were not reported due to the change of this response option and the small sample sizes. View Large Table 1. Sample Characteristics by Survey Year Among High School Students Aged <18 Years Old, YRBS 2001–2015   2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01    2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01  NH, non-Hispanic; AI/AN, American Indian or Alaska Native; NH/PI, Native Hawaiian or Other Pacific Islander; NS, not significant. ap Value for trend is based on univariate logistic regression model where survey years served as a continuous variable. bStudents who reported smoking >0 days in the past 30 days. cThe sum is not equal to 100% since the response options from “I bought them from a vending machine” in 2001–2013 and “I got them on the Internet” in 2015 were not reported due to the change of this response option and the small sample sizes. View Large Multivariable analyses of sources of cigarettes are presented in Table 2. The temporal trends were significant for two sources: a downward trend from 19.1% in 2001 to 12.6% in 2015 (aOR = 0.98, CI = [0.96–1.00]) of high school students buying their cigarettes in a store and an upward trend from 9.5% in 2001 to 16.5% in 2015 (aOR = 1.03, CI = [1.01–1.05]) of high school students getting cigarettes by “some other way.” Older high school students had higher odds of obtaining their cigarettes by buying them in a store (aOR = 2.45, CI = [2.11–2.85]) but lower odds of obtaining their cigarettes by taking them “from a store or family member” (aOR = 0.50, CI = [0.42–0.59]) or by “some other way” (aOR = 0.52, CI = [0.46–0.60]) than did younger students. As compared to female students, male students were more likely to buy their cigarettes in a store (aOR = 1.86, CI = [1.64–2.12]) or get their cigarettes by “some other way” (aOR = 1.27, CI = [1.11–1.45]), but less likely to report that they gave someone else money to buy cigarettes (aOR = 0.70, CI = [0.63–0.77]), or that “a person 18 years old or older gave them to me” (aOR = 0.66, CI = [0.57–0.75]). As compared to white students, black and Hispanic students had higher odds of obtaining their cigarettes by buying them in a store, taking them from a store or family member, or by “some other way,” but lower odds of getting their cigarettes by giving someone else money to buy them, or borrowing/bumming them from someone else. As compared to current smokers at the low level, daily smokers and smokers at the medium level were more likely to obtain their cigarettes by buying them in a store or giving someone else money to buy them, but less likely to obtain their cigarettes from other sources. Table 2. Multivariable Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS  NH, non-Hispanic; REF, reference; NS, not significant. aCurrent smokers were students who reported smoking >0 days in the past 30 days. Each source was treated as a dependent variable and analyzed by a separate logistic regression model. The aOR is adjusted by year, age, sex, race/ethnicity, and smoking frequency. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR for race/ethnicity other than white, black, and Hispanic students were not reported due to the small sample sizes. View Large Table 2. Multivariable Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS  NH, non-Hispanic; REF, reference; NS, not significant. aCurrent smokers were students who reported smoking >0 days in the past 30 days. Each source was treated as a dependent variable and analyzed by a separate logistic regression model. The aOR is adjusted by year, age, sex, race/ethnicity, and smoking frequency. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR for race/ethnicity other than white, black, and Hispanic students were not reported due to the small sample sizes. View Large In Table 3, we present the trend aOR for sources of cigarettes from stratified analyses by age, sex, race/ethnicity, and smoking frequency. The prevalence of high school students who bought cigarettes in a store significantly declined among smokers aged 16–17 (aOR = 0.98, CI = [0.96–1.00]), male smokers (aOR = 0.97, CI = [0.95–0.99]), white smokers (aOR = 0.97, CI = [0.95–1.00]), and daily smokers (aOR = 0.96, CI = [0.93–0.99]), but the trend was not significant among other categories. The prevalence of high school students getting cigarettes “some other way” significantly increased across all groups except Hispanic smokers and medium-level or daily smokers. We did not find any significant trends in the stratified analyses for two social sources (“gave someone else money to buy them for me” and “a person 18 years or older gave them to me”). The prevalence of students who reported obtaining their cigarettes by borrowing/bumming them from someone else significantly declined among Hispanic smokers (aOR = 0.97, CI = [0.95–1.00) and low-level smokers (aOR = 0.97, CI = [0.95–1.00]), but it significantly increased among daily smokers (aOR = 1.06, CI = [1.02–1.11]). The prevalence of obtaining cigarettes by taking them “from a store or family member” significantly increased among smokers aged ≤15 (aOR = 1.03, CI = [1.00–1.05], female smokers (aOR = 1.04, CI = [1.02–1.07]), Hispanic smokers (aOR = 1.04, CI = [1.01–1.08]), and low-level smokers (aOR = 1.03, CI = [1.01–1.06]). Table 3. Stratified Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS  NH, non-Hispanic; NS, not significant. aStudents who reported smoking >0 days in the past 30 days. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR was adjusted by sex, race/ethnicity, and smoking frequency. daOR was adjusted by age, race/ethnicity, and smoking frequency. eaOR was adjusted by age, sex, and smoking frequency. faOR was adjusted by age, sex, and race/ethnicity. View Large Table 3. Stratified Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS  NH, non-Hispanic; NS, not significant. aStudents who reported smoking >0 days in the past 30 days. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR was adjusted by sex, race/ethnicity, and smoking frequency. daOR was adjusted by age, race/ethnicity, and smoking frequency. eaOR was adjusted by age, sex, and smoking frequency. faOR was adjusted by age, sex, and race/ethnicity. View Large Summary and Discussion This study analyzed sources of cigarettes among high school students under 18 years old during 2001–2015 using a large and nationally representative sample. Overall, we observed a declining trend of smoking prevalence, with the current smoking prevalence dropping from 26.9% in 2001 to 9.9% in 2015. The drop in smoking prevalence was more pronounced among smokers at the medium level (8.5% to 2.8%) and daily smokers (9.0% to 1.9%) as compared to current smokers at the low level (9.3% to 5.2%). Consistent with previous studies,13–15,20–25 we found that store purchases accounted for a small percentage of youth acquisition of cigarettes and a majority of youth usually obtained their cigarettes from social sources (ie, “gave someone else money to buy them for me,” “borrowed or bummed them from someone else,” “a person 18 years old gave them to me,” “took from a store or family member”) and “some other way.” Legislation along with social and demographic factors can impact where and how youth smokers get their cigarettes. This study found an overall downward trend of current high school smokers buying their cigarettes in a store. Our findings are generally consistent with other two studies on temporal trends of youth cigarette acquisition.13,14 This overall downward trend could be explained by enforcement of youth access laws to prohibit underage tobacco sales. For instance, under the 2009 Family Smoking Prevention and Tobacco Control Act (FSPTCA), the Food and Drug Administration (FDA) has been routinely inspecting tobacco retailers’ compliance with underage sales laws. Studies show that regular compliance checks along with penalties imposed for retailer violations can significantly reduce youth access to cigarettes.26 The analysis of FDA compliance inspections further shows that state-level cigarette tax and tobacco prevention spending toward the Centers for Disease Control recommended funding targets might also help reduce tobacco retailers’ violation rate for sales to minors.27 The results of this study indicate that older students (vs. younger students), male students (vs. female students), black and Hispanic students (vs. white students), and daily or smokers at the medium level (vs. smokers at the low level) were more likely to buy their cigarettes from a store. It is promising to identify a significantly decreasing trend in purchasing cigarettes from a store among these high-risk populations from stratified analyses, which supports continued emphasis on enforcing underage sales restrictions.26 The key elements of enforcement include clarifying enforcement responsibilities, providing adequate funding, setting goals for retailer compliance rates, and imposing penalties for violations.28 To further reduce disparities of youth access cigarettes in stores, retailer inspection programs may consider oversampling retailers in areas with higher likelihood of sales to minors. There was an overall upward trend of young smokers obtaining cigarettes by “some other way.” For instance, 9.5% of high school students reported that they got cigarettes some other way in 2001, increasing to 16.5% in 2015. Furthermore, the upward trends were significant among most demographic groups (except Hispanic students). However, it is unclear what “some other way” means. Future surveys should clearly define this category and further investigate the driving factors for this cigarette access source. In the multivariable analysis, we did not observe significant trends in four other social sources from which youth obtained their cigarettes: “gave someone else money to buy them for me,” “borrowed (or bummed) them from someone else,” “a person 18 years or older gave them to me,” and “took from a store or family member.” The lack of significant trends for these sources could be due to two plausible reasons. First, we found there are different patterns of social access trajectories by age, sex, race/ethnicity, and smoking frequency through the stratified analysis. For instance, the prevalence of obtaining cigarettes by borrowing/bumming them from someone else significantly decreased among low-level smokers, but significantly increased among daily smokers. Disparities in cigarette access must be reduced across subgroups in order to achieve an overall declining trend. Second, youth under age 18 often obtain their cigarettes from young adults aged 18–25 years.3 During 2001–2015, the minimum sales age for tobacco was 18 years old in most regions of the United States, and policies restricting youth access to tobacco did not significantly change over the survey period. Since 2015, two states and at least 245 municipalities have implemented the Tobacco 21 policy,29 which prohibits the distribution or sale of tobacco products, including cigarettes, chewing tobacco, hookah, e-cigarettes, and liquid nicotine, to individuals under the age of 21. A pilot study of Tobacco 21 in Needham, MA,30 the first municipality in United States to implement the policy in 2005, has shown promise in reducing youth smoking. Tobacco 21 laws make the minimum age for purchasing tobacco products consistent with the minimum legal drinking age, and this consistency could simplify ID checks for retailers as driver’s licenses look different for those under 21 years old in many states.31 We conjecture that the Tobacco 21 campaign could prevent youth from getting cigarettes through social sources. Continuous monitoring of youth tobacco access trends and evaluation of their association with Tobacco 21 is critically needed. Our findings underscore the heterogeneity of youth cigarette acquisition from social sources and the disparities by age, sex, race/ethnicity, and smoking frequency. Male students were less likely than female students to give someone else money to buy cigarettes for them or to get them from a person 18 years or older. Black and Hispanic students were less likely than white students to give someone else money to buy cigarettes for them or to borrow/bum cigarettes. Daily smokers and smokers at the medium level were more likely to give someone else money to buy cigarettes for them, but less likely to rely on other social sources to obtain cigarettes than were smokers at the low level. Tailored interventions and educational campaigns should be developed to reach a large audience and further reduce youth access to cigarettes from social sources. Such strategies may include raising the minimum smoking age to 21, denormalizing smoking behaviors among peers, and implementing smoke-free home and vehicle rules. This study has several limitations. First, the YRBS is school-based survey of students from the 9th through 12th grades. By excluding high school dropouts and homeschooled students, the school-based survey might not be generalizable to the wider youth population. Second, data on sources of cigarettes among high school students were self-reported and thus might be subject to recall and other forms of self-reported bias.32 In addition, participants were able to select only one source for how they usually obtain cigarettes. This might introduce additional bias. Third, the study utilized the YRBS national data and therefore we were not able to identify the geographic differences. Because tobacco policies, including smoke-free policies and cigarette price increases, are different across geographic regions, the temporal trends of youth sources of cigarettes might have spatial variance. Future research should address the regional difference and evaluate the impacts of various tobacco policies on the sources of youth cigarette acquisition. Finally, small sample sizes limited the analyses of temporal trends of obtaining cigarettes from a vending machine or on the Internet. This study extends current literature by examining the temporal trends in sources of cigarettes among high school students from 2001 to 2015. We found an overall downward trend of buying cigarettes in a store, while identifying an overall upward trend of obtaining cigarettes from “some other way.” We also observed the heterogeneity in sources of cigarettes by age, sex, race/ethnicity, and smoking frequency. This heterogeneity highlights the importance of implementing tailored policies and interventions to reduce youth access to cigarettes and prevent youth from smoking. Declaration of Interests None declared. Acknowledgments Authors’ contribution: HD acquired data, conceptualized the study, performed analyses, drafted the initial manuscript, and approved the final manuscript as submitted. JH assisted in data analysis and result interpretation, and approved the final manuscript as submitted. 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Tob Control . 2000; 9( 2): 169– 176. Google Scholar CrossRef Search ADS PubMed  27. Dai H, Hao J. The effects of tobacco control policies on retailer sales to minors in the USA, 2015. Tob Control . 2017. 28. Campaign for Tobacco-Free Kids. Enforcing Laws Prohibiting Cigarette Sales to Kids Reducing Youth Smoking. 2010. www.tobaccofreekids.org/research/factsheets/pdf/0049.pdf. Accessed May 1, 2016. 29. Campaign for Tobacco-Free Kids. States and Localities that have Passed the Minimum Legal Sale Age for Tobacco Products to 21. 2017. www.tobaccofreekids.org/content/what_we_do/state_local_issues/sales_21/states_localities_MLSA_21.pdf. Accessed February 7, 2017. 30. Kessel Schneider S, Buka SL, Dash K, Winickoff JP, O’Donnell L. Community reductions in youth smoking after raising the minimum tobacco sales age to 21. Tob Control . 2016; 25( 3): 355– 359. Google Scholar CrossRef Search ADS PubMed  31. Winickoff JP, McMillen R, Tanski S, Wilson K, Gottlieb M, Crane R. Public support for raising the age of sale for tobacco to 21 in the United States. Tob Control . 2016; 25( 3): 284– 288. Google Scholar CrossRef Search ADS PubMed  32. Grimes DA, Schulz KF. Bias and causal associations in observational research. Lancet . 2002; 359( 9302): 248– 252. Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nicotine and Tobacco Research Oxford University Press

Temporal Trends of Sources of Cigarettes Among US High School Students: 2001–2015

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
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1462-2203
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1469-994X
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10.1093/ntr/nty001
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Abstract

Abstract Introduction Restricting the supply of cigarettes to youth plays an important role in reducing youth smoking. Methods The study included data from 8 years of the national Youth Risk Behavior Survey (YRBS) from 2001 to 2015 with 99572 high school students less than 18 years old. Data were weighted to provide national estimates of the temporal trends of cigarette sources. Each cigarette source was analyzed by a separate multivariable logistic regression model and the linear trend odds ratio (aOR) was adjusted by age, sex, race/ethnicity, and smoking frequency. Results The current smoking prevalence among US high school students less than 18 years of age declined from 26.9% in 2001 to 9.9% in 2015. Among current smokers, we found an overall downward trend of buying cigarettes in a store (aOR = 0.98, confidence interval [CI] = [0.96–1.00]) and an overall upward trend of getting them “some other way” (aOR = 1.03, CI = [1.01–1.05]). The prevalence of purchasing cigarettes in a store significantly declined among smokers aged 16–17, male smokers, white smokers, and daily smokers, but not among other categories. The prevalence of getting cigarettes “some other way” significantly increased across all groups except Hispanic smokers and medium-level or daily smokers. Conclusions The proportion of high school students reporting that they bought cigarettes from a store has been declining over the years, while the proportion of high schoolers reporting that they got cigarettes “some other way” has been increasing. The temporal trends also varied by age, sex, race/ethnicity, and smoking frequency. Implications Patterns of high school student access to cigarettes have changed from 2001 to 2015, with access from “some other way” becoming more prevalent. The differences in cigarette acquisition by age, sex, race/ethnicity, and smoking frequency highlight the importance of implementing tailored policies and interventions to reduce youth access to cigarettes and prevent youth from smoking. Introduction Cigarette smoking is the leading cause of preventable death in most countries. In the United States, smoking is responsible for more than 480000 deaths and $289 billion in direct health care expenditures and lost productivity each year.1–3 Youth are at the greatest risk of smoking, as evidenced by 9 out of 10 smokers having tried their first cigarette by age 18.4 Though the cigarette smoking prevalence among youth has been declining in recent years,3,5 9.3% of high school students reported smoking cigarettes in the past 30 days, and 2.3% of middle school students reported currently smoking cigarettes in 2015.6 It is estimated that 5.6 million youth currently aged 0–17 will die early from a cigarette smoking-related illness unless youth smoking rates drop rapidly.3 An important component in reducing youth smoking is to restrict the supply of cigarettes to youth. Control of youth access to cigarettes has been included in the Best Practices for Comprehensive Tobacco Control Programs from the Centers for Disease Control and Prevention7 as well as Healthy People 2020.8 The sources of cigarettes among youth can be grouped into 2 general categories: commercial sources (buying from a store or on the Internet) and social sources (borrowing, buying, or taking from others). Though federal laws restrict the sales of cigarettes to youth under 18 years old, past studies have raised concerns about the effectiveness of such regulation.9,10 More than 60% of responders from the 2014 National Youth Tobacco Survey11 think it is “easy” or “somewhat easy” for youth to buy tobacco products in stores. In addition, youth are acquiring cigarettes from social sources, such as friends or family members. Past studies have shown that younger adolescents (vs. older youth) and nondaily smokers (vs. daily smokers) were more likely to obtain their cigarettes from social sources.12–15 Examining each of these sources of youth cigarette acquisition—social and commercial—is important to further reduce youth smoking. Given the changes in tobacco control policies, such as increased cigarette prices and enforcement of retail compliance with underage sales laws, it is reasonable to expect that youth might shift their sources of cigarette acquisition over time. A few studies examined the temporal trend of youth access to cigarettes and identified shifts in sources of where youth obtained their cigarettes.13,14 Jones et al.13 analyzed the 1995, 1997, and 1999 national Youth Risk Behavior Surveys and found that relying on store purchases significantly decreased from 38.7% in 1995 to 23.5% in 1999, while giving someone else money to buy cigarettes significantly increased. Lenk et al.14 studied trends in sources of cigarettes among adolescents from 2000 to 2006 in Minnesota and identified a downward trend of youth buying cigarettes from stores but an upward trend in stealing cigarettes from others. However, these studies either relied on data before 200013 or focused on a regional trend.14 To the best of our knowledge, no recent study has examined the temporal trends of youth access to cigarettes at the national level and assessed heterogeneity in the ways youth obtain cigarettes, such as variations by demographic status and smoking frequency. To fill the gaps in knowledge, we used a national survey from 2001 to 2015 to analyze the temporal trends of youth access to cigarettes, overall and stratified by smoking frequency and demographic characteristics. This study provides policy makers and school administrators with information and analysis to assist them in formulating strategies to control the supply of cigarettes to youth more effectively and further prevent youth from smoking. Data and Methods Data The data were collected from the national Youth Risk Behavior Survey (YRBS). The YRBS has been conducted biennially in odd-numbered years since 1991 using a nationally representative sample of high school students in grades 9–12 in the United States. The national YRBS uses a three-stage, cluster sample design. A detailed description of YRBS survey design and data collection can be found on the YRBS website.16–18 The study included data from 8 years of the YRBS from 2001 to 2015 with a total of 117815 respondents. The overall response rates (the product of the school response rate and the student response rate) varied from 60% (2015) to 71% (2009 and 2011), with a median of 68%. Since the minimum age to purchase cigarettes was 18 in most states from 2001 to 2015, students who identified themselves as ≥18 years old were excluded from this study (n = 18388). A total of 99572 respondents aged under 18 years from eight surveys (the 2001–2015 YRBS) were included in the analysis. Measures Youth Access to Cigarettes Youth access to cigarettes was based on the response to the question, “During the past 30 days, how did you usually get your own cigarettes? (Select only one response.)” The response options included “A. I did not smoke cigarettes during the past 30 days,” “B. I bought them in a store such as a convenience store, supermarket, discount store, or gas station,” “C. I bought them from a vending machine,” “D. I gave someone else money to buy them for me,” “E. I borrowed (bummed) them from someone else,” “F. A person 18 years old or older gave them to me,” “G. I took them from a store or family member,” “H. I got them some other way.” This question was first asked in the 1995 YRBS, but the response options were provided differently in the 1995–1999 surveys, and thus the 3 surveys from this period were not included in this study. In 2015, the response option C was changed to “C. I got them on the Internet.” Due to the change of this response option and small sample sizes, we did not report the response option C in this study. Current Smokers and Smoking Frequency Current smokers were defined as those who reported smoking >0 days in the past 30 days13 in response to the item, “During the past 30 days, on how many days did you smoke cigarettes?” Response options included “0 days,” “1 or 2 days,” “3 to 5 days,” “6 to 9 days,” “10 to 19 days,” “20 to 29 days,” and “all 30 days.” Based on the frequency of smoking, we further classified current smokers into 3 groups: low (1–5 days), medium (6–29 days), and daily smokers (30 days). Covariates To control for other influences, several covariates were included in the analysis, including sex (male or female), race/ethnicity (non-Hispanic (NH) white, NH-black, Hispanic, NH-American Indian or Alaska Native (AI/AN), NH-Asian, NH-Native Hawaiian or Other Pacific Islander (NH/PI), NH-others), and age (≤15 years old or 16–17 years old). Method Data were weighted to provide national estimates by accounting for the oversampling of black and Hispanic students and for nonresponse. First, weighted % and 95% confidence interval (CI) of demographic characteristics, smoking prevalence, and sources of cigarettes among high school students were reported from 2001 to 2015. Temporal trends were examined based on univariate logistic regression analyses where survey years served as a continuous variable. Second, separate multivariable logistic regression models were used to examine temporal trends of smokers obtaining their cigarettes from each source. Trend odds ratio (aOR) and 95% CI for cigarette sources, adjusted by age, sex, race/ethnicity, and smoking frequency, were reported in the multivariable analysis. Third, stratified analyses were further performed to evaluate temporal trends of each cigarette source by age, sex, race/ethnicity, and smoking frequency. Data were analyzed using SAS 9.4 (Cary, NC) survey procedures to account for the nested design of YRBS and weighting.19 A p-value <.05 was considered statistically significant. Results As shown in Table 1, the current smoking prevalence among US high school students less than 18 years old declined from 26.9% in 2001 to 9.9% in 2015 (p < .01). The distributions of respondents’ age and sex were relatively stable from 2001 to 2015, while fewer white students (from 67.1% in 2001 to 54.0% in 2015, p < .01) and more Hispanic students (from 12.1% in 2001 to 22.5% in 2015, p < .01) were included in the surveys. The prevalence of current smokers declined from 9.4% to 5.2% for smokers at the low level (p < .01), from 8.5% to 2.8% for smokers at the medium level (p < .01), and 9.0% to 1.9% for daily smokers (p < .01). Among current smokers, the proportion of high school students getting their cigarettes from different sources along with their p-values from univariate trend analysis was also presented in Table 1. Table 1. Sample Characteristics by Survey Year Among High School Students Aged <18 Years Old, YRBS 2001–2015   2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01    2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01  NH, non-Hispanic; AI/AN, American Indian or Alaska Native; NH/PI, Native Hawaiian or Other Pacific Islander; NS, not significant. ap Value for trend is based on univariate logistic regression model where survey years served as a continuous variable. bStudents who reported smoking >0 days in the past 30 days. cThe sum is not equal to 100% since the response options from “I bought them from a vending machine” in 2001–2013 and “I got them on the Internet” in 2015 were not reported due to the change of this response option and the small sample sizes. View Large Table 1. Sample Characteristics by Survey Year Among High School Students Aged <18 Years Old, YRBS 2001–2015   2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01    2001  2003  2005  2007  2009  2011  2013  2015  p Value for trenda  No. of respondents  11392  12804  11645  11872  13815  13143  11263  13493  Noncurrent smoker  73.1 (71.1–75.1)  79.2 (77–81.3)  77.9 (75.5–80.3)  81.4 (78.9–83.8)  81.8 (80.0–83.5)  83.6 (82.0–85.2)  85.2 (82.8–87.7)  90.1 (88.3–91.8)  <.01  Current smokerb  26.9 (24.9–28.9)  20.8 (18.7–23)  22.1 (19.7–24.5)  18.6 (16.2–21.1)  18.2 (16.5–20.0)  16.4 (14.8–18.0)  14.8 (12.3–17.2)  9.9 (8.2–11.7)  <.01   Low (1–5 days)  9.4 (8.5–10.2)  7.2 (6.3–8.1)  8.8 (7.9–9.8)  7.5 (6.6–8.4)  7.8 (7.0–8.7)  7.7 (6.9–8.6)  6.7 (5.8–7.6)  5.2 (4.3–6.1)  <.01   Medium (6–29 days)  8.5 (7.7–9.4)  6.8 (5.9–7.6)  6.7 (5.9–7.4)  5.8 (4.8–6.8)  5.8 (5.2–6.5)  4.8 (4.2–5.4)  4.6 (3.9–5.4)  2.8 (2.2–3.4)  <.01   Daily (30 days)  9.0 (7.8–10.2)  6.9 (5.7–8.1)  6.6 (5.3–7.9)  5.4 (4.1–6.6)  4.6 (3.8–5.4)  3.9 (3.2–4.6)  3.5 (2.3–4.6)  1.9 (1.4–2.5)  <.01  Age   ≤15 years old  42.5 (40.5–44.5)  43.4 (41.7–45.1)  42.9 (41.3–44.5)  43.3 (41.6–45)  42 (40.2–43.7)  42.4 (40.3–44.5)  40.8 (39.3–42.4)  42.7 (40.9–44.6)  NS   >15 years old  57.5 (55.5–59.5)  56.6 (54.9–58.3)  57.1 (55.5–58.7)  56.7 (55–58.4)  58 (56.3–59.8)  57.6 (55.5–59.7)  59.2 (57.6–60.7)  57.3 (55.4–59.1)  NS  Sex   Female  52.2 (49.9–54.5)  49.2 (47.7–50.7)  50.2 (49.2–51.3)  49.8 (48.5–51.2)  48.3 (45.7–50.9)  49.1 (47.1–51)  50.6 (49.3–52.0)  49.6 (46.7–52.5)  NS   Male  47.8 (45.5–50.1)  50.8 (49.3–52.3)  49.8 (48.7–50.8)  50.2 (48.8–51.5)  51.7 (49.1–54.3)  50.9 (49–52.9)  49.4 (48.0–50.7)  50.4 (47.5–53.3)  NS  Race/ethnicity   NH-white  67.1 (62.6–71.7)  61.4 (53.6–69.2)  61.8 (54.8–68.8)  59.9 (52.5–67.3)  58.3 (50.8–65.8)  56.4 (49.0–63.9)  55.2 (47.0–63.4)  54.0 (46.2–61.8)  <.01   NH-black  13.1 (10.6–15.6)  13.7 (9.4–18.1)  14.7 (10.3–19.1)  15.1 (10.4–19.7)  14.2 (9.7–18.8)  14.1 (10.2–18.0)  14.3 (9.3–19.2)  13.8 (9.9–17.7)  NS   Hispanic  12.1 (9.0–15.1)  16.6 (11.8–21.4)  15.2 (10.9–19.6)  17.1 (12.5–21.6)  19 (14.2–23.9)  20.2 (14.7–25.8)  21.3 (15.9–26.6)  22.5 (16.1–28.8)  <.01   NH-Asian  3.4 (2.1–4.6)  3.2 (2.0–4.4)  3.3 (2.1–4.5)  3.6 (2.1–5)  3.5 (1.6–5.4)  3.2 (2.3–4.2)  3.1 (1.8–4.5)  3.8 (2.1–5.5)  NS   NH-AI/AN  0.7 (0.3–1.1)  1.1 (0.8–1.3)  1.0 (0.3–1.8)  1.0 (0.0–2.2)  0.6 (0.4–0.8)  0.8 (0.0–1.8)  0.7 (0.5–0.9)  0.6 (0.3–0.9)  NS   NH-NH/PI  0.7 (0.3–1.1)  1.0 (0.6–1.4)  0.8 (0.4–1.2)  0.8 (0.5–1.1)  0.8 (0.3–1.3)  1.0 (0.6–1.4)  0.9 (0.4–1.4)  0.7 (0.4–0.9)  NS   NH-others  2.9 (2.2–3.5)  3.0 (2.4–3.6)  3.1 (2.5–3.7)  2.6 (2.0–3.2)  3.6 (2.6–4.5)  4.2 (3.4–4.9)  4.6 (3.8–5.5)  4.6 (3.8–5.4)  <.01  Sources of youth cigarettes among current smokersc   I bought them in a store such as a convenience store, supermarket, discount store, or gas station  19.1 (16.8–21.4)  18.9 (16.2–21.6)  15.6 (12.9–18.3)  16.2 (12.9–19.6)  14.2 (11.4–16.9)  13.9 (11.4–16.4)  18.4 (14.7–22.0)  12.6 (9.3–15.9)  <.01   I gave someone else money to buy them for me  31.7 (28.7–34.8)  29.7 (25.4–34.0)  28.5 (25.4–31.5)  26.3 (23.4–29.3)  28.2 (25.3–31.1)  26.3 (23.6–29.0)  28.8 (25.4–32.3)  24.0 (20.2–27.8)  <.01   I borrowed (or bummed) them from someone else  26.6 (23.6–29.6)  24.6 (22.6–26.6)  26.9 (24.2–29.6)  27.9 (25.1–30.7)  28.0 (25.5–30.4)  26.9 (24.3–29.5)  27.2 (24.3–30.0)  31.1 (26.5–35.6)  NS   A person 18 years old or older gave them to me  7.9 (6.3–9.6)  8.6 (6.3–10.8)  10.3 (8.6–12)  10.5 (8.9–12.1)  10.6 (8.8–12.3)  9.4 (7.9–10.9)  8.4 (7.0–9.7)  8.9 (6.6–11.1)  NS   I took them from a store or family member  4.3 (3.2–5.4)  5.2 (4.1–6.3)  6.9 (5.5–8.3)  6.4 (5.1–7.7)  5.6 (4.4–6.8)  6.8 (5.6–8.1)  6.0 (4.2–7.8)  6.0 (4.2–7.7)  .03   I got them some other way  9.5 (8.0–11.0)  11.1 (9–13.1)  10.9 (9.1–12.7)  11.6 (10–13.3)  12.4 (10.6–14.2)  14.9 (12.6–17.2)  10.5 (8.2–12.8)  16.5 (13.7–19.3)  <.01  NH, non-Hispanic; AI/AN, American Indian or Alaska Native; NH/PI, Native Hawaiian or Other Pacific Islander; NS, not significant. ap Value for trend is based on univariate logistic regression model where survey years served as a continuous variable. bStudents who reported smoking >0 days in the past 30 days. cThe sum is not equal to 100% since the response options from “I bought them from a vending machine” in 2001–2013 and “I got them on the Internet” in 2015 were not reported due to the change of this response option and the small sample sizes. View Large Multivariable analyses of sources of cigarettes are presented in Table 2. The temporal trends were significant for two sources: a downward trend from 19.1% in 2001 to 12.6% in 2015 (aOR = 0.98, CI = [0.96–1.00]) of high school students buying their cigarettes in a store and an upward trend from 9.5% in 2001 to 16.5% in 2015 (aOR = 1.03, CI = [1.01–1.05]) of high school students getting cigarettes by “some other way.” Older high school students had higher odds of obtaining their cigarettes by buying them in a store (aOR = 2.45, CI = [2.11–2.85]) but lower odds of obtaining their cigarettes by taking them “from a store or family member” (aOR = 0.50, CI = [0.42–0.59]) or by “some other way” (aOR = 0.52, CI = [0.46–0.60]) than did younger students. As compared to female students, male students were more likely to buy their cigarettes in a store (aOR = 1.86, CI = [1.64–2.12]) or get their cigarettes by “some other way” (aOR = 1.27, CI = [1.11–1.45]), but less likely to report that they gave someone else money to buy cigarettes (aOR = 0.70, CI = [0.63–0.77]), or that “a person 18 years old or older gave them to me” (aOR = 0.66, CI = [0.57–0.75]). As compared to white students, black and Hispanic students had higher odds of obtaining their cigarettes by buying them in a store, taking them from a store or family member, or by “some other way,” but lower odds of getting their cigarettes by giving someone else money to buy them, or borrowing/bumming them from someone else. As compared to current smokers at the low level, daily smokers and smokers at the medium level were more likely to obtain their cigarettes by buying them in a store or giving someone else money to buy them, but less likely to obtain their cigarettes from other sources. Table 2. Multivariable Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS  NH, non-Hispanic; REF, reference; NS, not significant. aCurrent smokers were students who reported smoking >0 days in the past 30 days. Each source was treated as a dependent variable and analyzed by a separate logistic regression model. The aOR is adjusted by year, age, sex, race/ethnicity, and smoking frequency. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR for race/ethnicity other than white, black, and Hispanic students were not reported due to the small sample sizes. View Large Table 2. Multivariable Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Year (2001– 2015) trendb  0.98 (0.96–1.00)  0.03  1.00 (0.98–1.01)  NS  0.99 (0.98–1.01)  NS  1.01 (0.99–1.02)  NS  1.02 (1.00–1.04)  NS  1.03 (1.01–1.05)  <.01  Age   ≤15 years old  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   16–17 years old  2.45 (2.11–2.85)  <.01  1.04 (0.93–1.16)  NS  1.01 (0.90–1.14)  NS  1.16 (0.98–1.36)  NS  0.50 (0.42–0.59)  <.01  0.52 (0.46–0.60)  <.01  Sex   Male  1.86 (1.64–2.12)  <.01  0.70 (0.63–0.77)  <.01  0.95 (0.86–1.04)  NS  0.66 (0.57–0.75)  <.01  1.05 (0.89–1.23)  NS  1.27 (1.11–1.45)  <.01   Female  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  Race/ethnicityc   NH-white  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   NH-black  1.69 (1.33–2.15)  <.01  0.72 (0.59–0.87)  <.01  0.49 (0.41–0.58)  <.01  1.16 (0.94–1.43)  NS  1.46 (1.10–1.93)  0.01  1.79 (1.48–2.17)  <.01   Hispanic  1.48 (1.26–1.75)  <.01  0.77 (0.68–0.88)  <.01  0.52 (0.45–0.60)  <.01  1.28 (1.09–1.51)  <.01  1.57 (1.27–1.94)  <.01  1.76 (1.52–2.04)  <.01  Smoking frequency   Low  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF  REF   Medium  2.25 (1.94–2.62)  <.01  3.37 (3.00–3.77)  <.01  0.35 (0.32–0.40)  <.01  0.82 (0.69–0.97)  .02  0.71 (0.57–0.87)  <.01  0.67 (0.56–0.81)  <.01   Daily  3.99 (3.39–4.69)  <.01  4.26 (3.73–4.87)  <.01  0.06 (0.05–0.08)  <.01  0.82 (0.69–0.98)  .03  0.60 (0.48–0.76)  <.01  1.04 (0.89–1.20)  NS  NH, non-Hispanic; REF, reference; NS, not significant. aCurrent smokers were students who reported smoking >0 days in the past 30 days. Each source was treated as a dependent variable and analyzed by a separate logistic regression model. The aOR is adjusted by year, age, sex, race/ethnicity, and smoking frequency. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR for race/ethnicity other than white, black, and Hispanic students were not reported due to the small sample sizes. View Large In Table 3, we present the trend aOR for sources of cigarettes from stratified analyses by age, sex, race/ethnicity, and smoking frequency. The prevalence of high school students who bought cigarettes in a store significantly declined among smokers aged 16–17 (aOR = 0.98, CI = [0.96–1.00]), male smokers (aOR = 0.97, CI = [0.95–0.99]), white smokers (aOR = 0.97, CI = [0.95–1.00]), and daily smokers (aOR = 0.96, CI = [0.93–0.99]), but the trend was not significant among other categories. The prevalence of high school students getting cigarettes “some other way” significantly increased across all groups except Hispanic smokers and medium-level or daily smokers. We did not find any significant trends in the stratified analyses for two social sources (“gave someone else money to buy them for me” and “a person 18 years or older gave them to me”). The prevalence of students who reported obtaining their cigarettes by borrowing/bumming them from someone else significantly declined among Hispanic smokers (aOR = 0.97, CI = [0.95–1.00) and low-level smokers (aOR = 0.97, CI = [0.95–1.00]), but it significantly increased among daily smokers (aOR = 1.06, CI = [1.02–1.11]). The prevalence of obtaining cigarettes by taking them “from a store or family member” significantly increased among smokers aged ≤15 (aOR = 1.03, CI = [1.00–1.05], female smokers (aOR = 1.04, CI = [1.02–1.07]), Hispanic smokers (aOR = 1.04, CI = [1.01–1.08]), and low-level smokers (aOR = 1.03, CI = [1.01–1.06]). Table 3. Stratified Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS  NH, non-Hispanic; NS, not significant. aStudents who reported smoking >0 days in the past 30 days. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR was adjusted by sex, race/ethnicity, and smoking frequency. daOR was adjusted by age, race/ethnicity, and smoking frequency. eaOR was adjusted by age, sex, and smoking frequency. faOR was adjusted by age, sex, and race/ethnicity. View Large Table 3. Stratified Analyses of Sources of Cigarettes Among Current Smokers,a YRBS 2001–2015   Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS    Students obtaining cigarettes from “bought them in a store”  Students obtaining cigarettes from “gave someone else money to buy them for me”  Students obtaining cigarettes from “borrowed (bummed) from someone else”  Students obtaining cigarettes from “a person 18 years old or older gave to me”  Students obtaining cigarettes from “took from a store or family member”  Students obtaining cigarettes from “some other way”    Trend aORb  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Trend aOR  p Value  Agec   ≤15 years old  0.99 (0.95–1.02)  NS  0.98 (0.96–1.00)  NS  0.98 (0.96–1.01)  NS  1.02 (0.99–1.05)  NS  1.03 (1.00–1.05)  .04  1.03 (1.01–1.05)  .02   16–17 years old  0.98 (0.96–1.00)  .02  1.00 (0.99–1.02)  NS  1.00 (0.98–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.04)  NS  1.03 (1.01–1.06)  <.01  Sexd   Female  0.99 (0.96–1.02)  NS  0.98 (0.97–1.00)  NS  0.99 (0.97–1.01)  NS  1.01 (0.99–1.03)  NS  1.04 (1.02–1.07)  <.01  1.04 (1.01–1.06)  <.01   Male  0.97 (0.95–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (0.87–1.21)  NS  1.00 (0.97–1.02)  NS  1.00 (0.97–1.02)  NS  1.03 (1.01–1.05)  .02  Race/ethnicitye   NH-white  0.97 (0.95–1.00)  .03  1.00 (0.98–1.01)  NS  1.00 (0.98–1.01)  NS  1.01 (0.99–1.03)  NS  1.01 (0.98–1.04)  NS  1.04 (1.02–1.06)  <.01   NH-black  0.98 (0.94–1.03)  NS  0.99 (0.95–1.04)  NS  0.96 (0.93–1.00)  NS  1.00 (0.95–1.04)  NS  1.03 (0.98–1.07)  NS  1.06 (1.02–1.11)  <.01   Hispanic  1.00 (0.97–1.03)  NS  1.00 (0.98–1.03)  NS  0.97 (0.95–1.00)  .04  1.00 (0.97–1.03)  NS  1.04 (1.01–1.08)  .01  1.01 (0.98–1.04)  NS  Current smokerf   Low (1–5 per day)  0.99 (0.97–1.02)  NS  1.02 (1.00–1.04)  NS  0.97 (0.96–0.99)  <.01  1.01 (0.99–1.03)  NS  1.03 (1.01–1.06)  .01  1.03 (1.00–1.05)  .02   Medium (6–29)  0.98 (0.96–1.01)  NS  1.00 (0.98–1.02)  NS  1.01 (0.99–1.03)  NS  1.01 (0.97–1.04)  NS  1.01 (0.98–1.05)  NS  1.00 (0.97–1.04)  NS   Daily (30)  0.96 (0.93–0.99)  0.01  0.98 (0.96–1.01)  NS  1.06 (1.02–1.11)  <.01  1.00 (0.97–1.03)  NS  0.99 (0.94–1.04)  NS  1.06 (1.04–1.09)  NS  NH, non-Hispanic; NS, not significant. aStudents who reported smoking >0 days in the past 30 days. bSurvey years (2001–2015) were treated as a continuous variable to detect linear trends. caOR was adjusted by sex, race/ethnicity, and smoking frequency. daOR was adjusted by age, race/ethnicity, and smoking frequency. eaOR was adjusted by age, sex, and smoking frequency. faOR was adjusted by age, sex, and race/ethnicity. View Large Summary and Discussion This study analyzed sources of cigarettes among high school students under 18 years old during 2001–2015 using a large and nationally representative sample. Overall, we observed a declining trend of smoking prevalence, with the current smoking prevalence dropping from 26.9% in 2001 to 9.9% in 2015. The drop in smoking prevalence was more pronounced among smokers at the medium level (8.5% to 2.8%) and daily smokers (9.0% to 1.9%) as compared to current smokers at the low level (9.3% to 5.2%). Consistent with previous studies,13–15,20–25 we found that store purchases accounted for a small percentage of youth acquisition of cigarettes and a majority of youth usually obtained their cigarettes from social sources (ie, “gave someone else money to buy them for me,” “borrowed or bummed them from someone else,” “a person 18 years old gave them to me,” “took from a store or family member”) and “some other way.” Legislation along with social and demographic factors can impact where and how youth smokers get their cigarettes. This study found an overall downward trend of current high school smokers buying their cigarettes in a store. Our findings are generally consistent with other two studies on temporal trends of youth cigarette acquisition.13,14 This overall downward trend could be explained by enforcement of youth access laws to prohibit underage tobacco sales. For instance, under the 2009 Family Smoking Prevention and Tobacco Control Act (FSPTCA), the Food and Drug Administration (FDA) has been routinely inspecting tobacco retailers’ compliance with underage sales laws. Studies show that regular compliance checks along with penalties imposed for retailer violations can significantly reduce youth access to cigarettes.26 The analysis of FDA compliance inspections further shows that state-level cigarette tax and tobacco prevention spending toward the Centers for Disease Control recommended funding targets might also help reduce tobacco retailers’ violation rate for sales to minors.27 The results of this study indicate that older students (vs. younger students), male students (vs. female students), black and Hispanic students (vs. white students), and daily or smokers at the medium level (vs. smokers at the low level) were more likely to buy their cigarettes from a store. It is promising to identify a significantly decreasing trend in purchasing cigarettes from a store among these high-risk populations from stratified analyses, which supports continued emphasis on enforcing underage sales restrictions.26 The key elements of enforcement include clarifying enforcement responsibilities, providing adequate funding, setting goals for retailer compliance rates, and imposing penalties for violations.28 To further reduce disparities of youth access cigarettes in stores, retailer inspection programs may consider oversampling retailers in areas with higher likelihood of sales to minors. There was an overall upward trend of young smokers obtaining cigarettes by “some other way.” For instance, 9.5% of high school students reported that they got cigarettes some other way in 2001, increasing to 16.5% in 2015. Furthermore, the upward trends were significant among most demographic groups (except Hispanic students). However, it is unclear what “some other way” means. Future surveys should clearly define this category and further investigate the driving factors for this cigarette access source. In the multivariable analysis, we did not observe significant trends in four other social sources from which youth obtained their cigarettes: “gave someone else money to buy them for me,” “borrowed (or bummed) them from someone else,” “a person 18 years or older gave them to me,” and “took from a store or family member.” The lack of significant trends for these sources could be due to two plausible reasons. First, we found there are different patterns of social access trajectories by age, sex, race/ethnicity, and smoking frequency through the stratified analysis. For instance, the prevalence of obtaining cigarettes by borrowing/bumming them from someone else significantly decreased among low-level smokers, but significantly increased among daily smokers. Disparities in cigarette access must be reduced across subgroups in order to achieve an overall declining trend. Second, youth under age 18 often obtain their cigarettes from young adults aged 18–25 years.3 During 2001–2015, the minimum sales age for tobacco was 18 years old in most regions of the United States, and policies restricting youth access to tobacco did not significantly change over the survey period. Since 2015, two states and at least 245 municipalities have implemented the Tobacco 21 policy,29 which prohibits the distribution or sale of tobacco products, including cigarettes, chewing tobacco, hookah, e-cigarettes, and liquid nicotine, to individuals under the age of 21. A pilot study of Tobacco 21 in Needham, MA,30 the first municipality in United States to implement the policy in 2005, has shown promise in reducing youth smoking. Tobacco 21 laws make the minimum age for purchasing tobacco products consistent with the minimum legal drinking age, and this consistency could simplify ID checks for retailers as driver’s licenses look different for those under 21 years old in many states.31 We conjecture that the Tobacco 21 campaign could prevent youth from getting cigarettes through social sources. Continuous monitoring of youth tobacco access trends and evaluation of their association with Tobacco 21 is critically needed. Our findings underscore the heterogeneity of youth cigarette acquisition from social sources and the disparities by age, sex, race/ethnicity, and smoking frequency. Male students were less likely than female students to give someone else money to buy cigarettes for them or to get them from a person 18 years or older. Black and Hispanic students were less likely than white students to give someone else money to buy cigarettes for them or to borrow/bum cigarettes. Daily smokers and smokers at the medium level were more likely to give someone else money to buy cigarettes for them, but less likely to rely on other social sources to obtain cigarettes than were smokers at the low level. Tailored interventions and educational campaigns should be developed to reach a large audience and further reduce youth access to cigarettes from social sources. Such strategies may include raising the minimum smoking age to 21, denormalizing smoking behaviors among peers, and implementing smoke-free home and vehicle rules. This study has several limitations. First, the YRBS is school-based survey of students from the 9th through 12th grades. By excluding high school dropouts and homeschooled students, the school-based survey might not be generalizable to the wider youth population. Second, data on sources of cigarettes among high school students were self-reported and thus might be subject to recall and other forms of self-reported bias.32 In addition, participants were able to select only one source for how they usually obtain cigarettes. This might introduce additional bias. Third, the study utilized the YRBS national data and therefore we were not able to identify the geographic differences. Because tobacco policies, including smoke-free policies and cigarette price increases, are different across geographic regions, the temporal trends of youth sources of cigarettes might have spatial variance. Future research should address the regional difference and evaluate the impacts of various tobacco policies on the sources of youth cigarette acquisition. Finally, small sample sizes limited the analyses of temporal trends of obtaining cigarettes from a vending machine or on the Internet. This study extends current literature by examining the temporal trends in sources of cigarettes among high school students from 2001 to 2015. We found an overall downward trend of buying cigarettes in a store, while identifying an overall upward trend of obtaining cigarettes from “some other way.” We also observed the heterogeneity in sources of cigarettes by age, sex, race/ethnicity, and smoking frequency. This heterogeneity highlights the importance of implementing tailored policies and interventions to reduce youth access to cigarettes and prevent youth from smoking. Declaration of Interests None declared. Acknowledgments Authors’ contribution: HD acquired data, conceptualized the study, performed analyses, drafted the initial manuscript, and approved the final manuscript as submitted. JH assisted in data analysis and result interpretation, and approved the final manuscript as submitted. 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Nicotine and Tobacco ResearchOxford University Press

Published: Jan 12, 2018

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