The Role of Physical Activity in the Association Between Smoking Status and Quality of Life

The Role of Physical Activity in the Association Between Smoking Status and Quality of Life Abstract Objectives Nonsmoking status and physical activity have, individually, been shown to be associated with health-related quality of life (HRQoL). The objective of this study was to assess whether the relationship between smoking status and HRQoL is modified or influenced by physical activity. Methods Data were extracted from the 2014 Behavioral Risk Factor Surveillance Survey dataset (N = 332680) in 2015. Logistic regression models were used to address study objectives. Health-related quality of life (HRQoL), measured using eight domains (general health, physical health, mental health, activity limitations, pain, depressive symptoms, anxiety, and vitality), was regressed on smoking status without and with adjustment for age, race, gender, education, marital status, income, employment, healthcare coverage, comorbidity, body mass index, flu vaccination, alcohol use, and physical activity. Smoking status by physical activity interaction term was added to the adjusted model and evaluated for significance. Results There were significant smoking status by physical activity interaction effects on general health, physical health, activity limitations, and depressive symptoms domains. Among those who exercised, relative differences in the odds of a high HRQoL was smaller between former smokers and nonsmokers and larger between current smokers and nonsmokers when compared to those who did not exercise. Similarly, there were sharper relative differences between those who exercised and those who did not exercise among former smokers than among current smokers. Conclusions Smokers who successfully quit smoking (former smokers) may benefit from enhanced HRQoL that tends towards that of nonsmokers if they adopt physical activity in their daily routine. Implications Behavioral interventions that combine smoking cessation and physical activity may be more effective than either smoking cessation or physical activity alone in improving the quality of life measures such as overall, physical and mental health, and degree of limitation to activities due to poor health. Health care providers can support patients who successfully quit smoking to add exercise to their daily routine with the expectation of enhanced HRQoL. Introduction There is strong evidence that smoking causes cancers, respiratory illnesses, and cardiovascular diseases and is associated with approximately 10 year reduction in life expectancy.1–4 These deleterious effects take time to manifest5,6 and may not be convincing reasons to quit smoking before they manifest. Smoking tends to cluster with other behavioral risk factors.7,8 For example, over 50% of US adults have at least two behavioral risk factors.7 This can have an additive or synergistic negative influence on chronic illness. It has been argued that patients may be more likely to quit smoking and not relapse if they experience immediate positive effects such as improvement in perceived health-related quality of life (HRQoL).9,10 HRQoL is a measure of an individual’s perception of physical, mental, and social well-being11,12 and may present additional opportunities for improving smoking cessation outcomes. A large number of studies examining the relationship between smoking status and HRQoL have found that smoking cessation improves HRQoL10,11,13–16 or that nonsmokers and former smokers have better HRQoL compared to current smokers.9,16–23 This suggests that smoking status is related to HRQoL. Physical activity has been shown to improve HRQoL.24 In particular, exercise training improves HRQoL among patients with cancers,25,26 chronic obstructive pulmonary disease,27 and cardiovascular disease.28–31 Recent findings from a smoking cessation trial by Bloom and colleagues suggest that being physically active may result in incremental improvements in HRQoL among smokers who successfully quit smoking.32 In particular, exercise was associated with improved mental well-being (but not physical or overall health) after taking into account smoking status at the end of the study period.32 However, the sample size for the trial was small (N = 61) and may not have been powered to detect changes in quality of life scores. We now use data from a large national cross-sectional study to assess whether physical activity modifies the association between smoking status and HRQoL. Methods Data were extracted from the 2014 Behavioral Risk Factor Surveillance System (BRFSS) secondary dataset in 2015. BRFSS is an on-going telephone-based survey system that assesses behavioral risk factors among non-institutionalized US population aged 18 years or older. The Centers for Disease Control and Prevention developed the survey and individual state health departments have conducted the survey annually since 1984. The 2014 survey includes participants from the 50 US states, the District of Columbia, Guam, and Puerto Rico who were selected using a stratified, multistage probability sampling design, incorporating random-digit-dialing methods for data collection via both landline and cellular telephones. Approval for this study was obtained from the University of Texas at Austin Office of Research Support. Study Sample Residents of the 50 US states and the District of Columbia and those who gave definitive responses to all variables of interest were included in the present study. Residents of Guam and Puerto Rico and those who gave inexact responses (“not sure” or “don’t know”) or had missing values on any variable of interest were excluded. Measures The dependent variables were eight quality of life indicators obtained from the sections of the BRFSS on health status and healthy days (health-related quality of life) in the core module and the section on healthy days (symptoms) in the optional module. The core module is used by all state health departments without modification in wording while the optional module is optional. The indicators measured general health, physical health, mental health, activity limitations, pain, depressive symptoms, anxiety symptoms, and vitality (Supplementary Appendix Table 1). Respondents were asked to rate their general health with the following response options provided: excellent, very good, good, fair, and poor. We dichotomized the responses as either (1) excellent/very good/good or (2) fair/poor. The responses of excellent, very good, or good were deemed “high HRQoL.” For the remaining HRQoL variables, respondents were asked to provide the number of days during the past 30 days that they felt a certain way. We dichotomized the frequency into: ≥14 days and <14 days. Less than 14 days of poor physical health, poor mental health, activity limitations, pain, depressive symptoms, and anxiety symptoms were deemed “high HRQoL.” Likewise, reporting feeling full of energy for 14 or more days was deemed “high HRQoL.” The use of binary data for quality of life indicators is consistent with other studies that assessed the relationship between smoking and HRQoL using BRFSS data.9,21 Determination of smoking status was based on two self-reported questions: (1) “Have you smoked at least 100 cigarettes in your entire life?” and (2) “Do you now smoke cigarettes every day, some days, or not at all?” Respondents who had smoked <100 cigarettes in their entire life were classified as nonsmokers, those who had smoked ≥100 cigarettes in their entire life and were “now” smoking every day or some days were classified as current smokers, whereas those who had smoked ≥100 cigarettes in their entire life but were “now” not smoking at all were classified as former smokers. We also extracted demographic variables (age, race, gender, educational attainment, marital status, income, and employment status), clinical variables (healthcare coverage, comorbidity, and body mass index), and behavioral variables (alcohol use within the past 30 days, flu vaccination within the past 12 months, and physical activity within the past month). The comorbidity variable was derived from recoding the items in the section on chronic health conditions. This section was introduced with the question: “Has a doctor, nurse, or other health professional EVER told you that you had any of the following?” Respondents were classified as not having a comorbid condition if they responded “no” to the following conditions: myocardial infarction, coronary heart disease, stroke, asthma, cancer, chronic obstructive pulmonary disease, arthritis depression, kidney disease, and diabetes. Respondents were classified as having a comorbid condition if they reported having a diagnosis of any of the previously listed conditions. Respondents who reported that they had “ever” been told that they had asthma were asked the follow-up question: “Do you still have asthma?” We classified those who responded “yes” to this follow-up question as having asthma and those who responded ‘no’ as not having asthma. Female respondents who reported that they had ‘ever’ been told that they diabetes were asked the follow-up question: “Was this only when you were pregnant?” We classified those who responded that they had been told they had diabetes only during pregnancy as not having diabetes and those who had been told they had diabetes at other times as having diabetes. Statistical Analysis Demographic, clinical, and behavioral variables were summarized using frequencies and percentages. Chi-square analysis was used to determine whether there were differences among (1) nonsmokers, (2) former smokers, and (3) current smokers based on demographic, clinical, and behavioral characteristics. For each quality of life indicator, unadjusted and adjusted logistic regression models were used to assess the relationship between smoking status and HRQoL. We adjusted for demographic, clinical, and behavioral variables. We also included the smoking status by exercise interaction term to the adjusted models and evaluated whether the interaction term was significant. For all analyses, we adjusted for the complex sampling design of the survey data. Data analyses were performed using SAS version 9.4 (SAS Institute, Inc, Cary, North Carolina). To control for multiple tests, we used Bonferonni-corrected p values where p < .05 for a significant global test. Results The 2013 BRFSS included data from 464664 (weighted n = 248482532) adult respondents. After the exclusion of residents of Guam and Puerto Rico (8506) and those who gave inexact responses or had missing values on any variable of interest (123478), the final sample size for our study was 332680 (weighted n = 173278039). According to our definition of smoking status, 56.9% were nonsmokers, 25.3% were former smokers, and 17.8% were current smokers. Table 1 shows the differences between nonsmokers, former smokers, and current smokers categorized by demographic, clinical, and behavioral characteristics. Compared to nonsmokers, former smokers were more likely to be 65 years or older, White, have at least one comorbidity, report using alcohol within the past 30 days, and report receiving a flu vaccination within the past 12 months. On the other hand, current smokers were more likely to be uncoupled (divorced, widowed, separated, or never married) and earn less than $20000 and less likely to have graduated college, have health care coverage or engage in physical activity. Table 1. Differences Among Nonsmokers, Former Smokers, and Current Smokers According to Demographic, Clinical, and Lifestyle Characteristics (N = 332680; Weighted N = 173278039) Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  *Statistically significant at p < .0001. aN = 183299; Weighted n = 98617039. bN = 98346; Weighted n = 43877591. cN = 51035; Weighted n = 30783409. View Large Table 1. Differences Among Nonsmokers, Former Smokers, and Current Smokers According to Demographic, Clinical, and Lifestyle Characteristics (N = 332680; Weighted N = 173278039) Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  *Statistically significant at p < .0001. aN = 183299; Weighted n = 98617039. bN = 98346; Weighted n = 43877591. cN = 51035; Weighted n = 30783409. View Large Table 2 shows the odds of a high HRQoL for former smokers and current smokers compared to nonsmokers. Table 3 shows the odds of having high HRQoL for those who exercise compared to those who do not. The adjusted models in Tables 2 and 3 are identical. However, different post hoc tests are represented in the tables. Overall, former smokers and current smokers had lower odds of having high HRQoL compared to nonsmokers. The odds were lower for current smokers than for former smokers. Conversely, those who exercised had higher odds of having high HRQoL compared to those who did not exercise. There were significant interactions between smoking status and physical activity on the general health, physical health, activity limitations, and depressive symptoms domains. There were smaller relative differences in the odds of a high HRQoL between former smokers and nonsmokers among those who exercised than among those who did not exercise. That is, the odds ratios for former smokers were closer to 1 among those who exercised relative to those who did not exercise (Table 2). Also, there were sharper differences in the odds of a high HRQoL between current smokers and nonsmokers among those who exercised than among those who did not exercise. That is, the odds ratios for current smokers were further away from 1 among those who exercised compared to those who did not exercise (Table 2). Similarly, there were sharper relative differences between those who exercised and those who did not exercise among former smokers than among current smokers. In other words, the odds ratios for those who exercised were further away from 1 among former smokers compared to current smokers (Table 3). Table 2. Odds of High Health-Related Quality of Life Based on Smoking Status and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  aHealth-related quality of life (HRQoL) regressed on smoking status. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by smoking status at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 2. Odds of High Health-Related Quality of Life Based on Smoking Status and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  aHealth-related quality of life (HRQoL) regressed on smoking status. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by smoking status at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 3. Odds of High Health-Related Quality of Life Based on Physical Activity and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  aHealth-related quality of life (HRQoL) regressed on exercise. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by engagement in physical activity at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 3. Odds of High Health-Related Quality of Life Based on Physical Activity and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  aHealth-related quality of life (HRQoL) regressed on exercise. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by engagement in physical activity at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Discussion Smoking cessation11,13–16 and physical activity24 have, individually, been shown to improve HRQoL. This supports our overall finding of higher HRQoL among former smokers and those who exercise relative to smokers and those who do not exercise. Our study assessed whether there is an interaction between smoking status and engagement in physical activity in their association with HRQoL. We found evidence to support this question on four quality of life domains: general health, physical health, activity limitations, and depressive symptoms. On these domains, differences in HRQoL between former smokers and nonsmokers were stronger among those who did not exercise than among those who did. This indicates that smokers who quit smoking may experience HRQoL that more closely approximates that of nonsmokers if they include physical activity in their lifestyle. This could be beneficial to former smokers, given that former smokers tend to have poorer quality of life when compared to nonsmokers.9,18,19,23 A similar argument also holds when comparing the relationship between physical activity and HRQoL by smoking status. Differences in HRQoL between those who exercised and those who did not were stronger among former smokers than among current smokers. On the four domains with significant interaction effects, former smokers who exercised had 70% to 160% higher odds of a high HRQoL than those who did not exercise (Table 3). On the other hand, the odds of a high HRQoL ranged from 20% to 110% higher for smokers who exercised relative to those who did not exercise. This implies that physical activity alone may not sufficiently improve overall well-being experienced by individuals who smoke. It is important to note that the ideal option would be not to initiate smoking since a higher proportion of nonsmokers had high HRQoL compared to former smokers on all HRQoL measures (Table 2). The study implications are particularly important for program planners who design lifestyle interventions and for health care professionals who advise and assist patients to make lifestyle changes. The findings are also important for patients with medical illness. Medical illness has been shown to motivate individuals who smoke to quit smoking.33,34 Individuals with medical illness are also more likely to make other lifestyle changes such as adopting physical activity.35 Hence, behavioral interventions that combine smoking cessation and physical activity may be more effective than either smoking cessation or physical activity alone in improving quality of life measures such as overall, physical and mental health, and degree of limitation to activities due to poor health. Additionally, health care providers can support patients who successfully quit smoking to add exercise to their daily routine with the expectation that they would experience enhanced improvement in their overall well-being. The study has several limitations. The strength of our evidence is weakened by the cross-sectional design of our study. Although the smoking cessation trial by Bloom and colleagues,32 of which our study is a replication, may have offered stronger evidence given its randomized controlled design, it also faced challenges that limited the power of the study and compromised its randomized design. We make up for some of our shortcoming by our large sample and national representativeness of the sample. However, our use of case-wise deletion of missing data may have introduced some bias as it is possible that participants excluded from the study may have been different from our final study sample. To conclude, smoking and lack of physical activity are associated with poor quality of life. Physical activity may have an additive effect in improving HRQoL among smokers who quit smoking such that their well-being tends towards that of nonsmokers. Health care providers may advise and support their patients to combine engagement in physical activity and smoking cessation or non-initiation of smoking with the aim of improving their general and physical health as well as alleviating activity limitations and depressive symptoms. Further research should include adequately powered intervention studies to validate our findings. Supplementary Material Supplementary data is available at Nicotine & Tobacco Research online Funding No financial disclosures were reported by the authors of this paper Declaration of Interests The authors have no conflicts of interest to declare. References 1. 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The Role of Physical Activity in the Association Between Smoking Status and Quality of Life

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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.
ISSN
1462-2203
eISSN
1469-994X
D.O.I.
10.1093/ntr/nty052
Publisher site
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Abstract

Abstract Objectives Nonsmoking status and physical activity have, individually, been shown to be associated with health-related quality of life (HRQoL). The objective of this study was to assess whether the relationship between smoking status and HRQoL is modified or influenced by physical activity. Methods Data were extracted from the 2014 Behavioral Risk Factor Surveillance Survey dataset (N = 332680) in 2015. Logistic regression models were used to address study objectives. Health-related quality of life (HRQoL), measured using eight domains (general health, physical health, mental health, activity limitations, pain, depressive symptoms, anxiety, and vitality), was regressed on smoking status without and with adjustment for age, race, gender, education, marital status, income, employment, healthcare coverage, comorbidity, body mass index, flu vaccination, alcohol use, and physical activity. Smoking status by physical activity interaction term was added to the adjusted model and evaluated for significance. Results There were significant smoking status by physical activity interaction effects on general health, physical health, activity limitations, and depressive symptoms domains. Among those who exercised, relative differences in the odds of a high HRQoL was smaller between former smokers and nonsmokers and larger between current smokers and nonsmokers when compared to those who did not exercise. Similarly, there were sharper relative differences between those who exercised and those who did not exercise among former smokers than among current smokers. Conclusions Smokers who successfully quit smoking (former smokers) may benefit from enhanced HRQoL that tends towards that of nonsmokers if they adopt physical activity in their daily routine. Implications Behavioral interventions that combine smoking cessation and physical activity may be more effective than either smoking cessation or physical activity alone in improving the quality of life measures such as overall, physical and mental health, and degree of limitation to activities due to poor health. Health care providers can support patients who successfully quit smoking to add exercise to their daily routine with the expectation of enhanced HRQoL. Introduction There is strong evidence that smoking causes cancers, respiratory illnesses, and cardiovascular diseases and is associated with approximately 10 year reduction in life expectancy.1–4 These deleterious effects take time to manifest5,6 and may not be convincing reasons to quit smoking before they manifest. Smoking tends to cluster with other behavioral risk factors.7,8 For example, over 50% of US adults have at least two behavioral risk factors.7 This can have an additive or synergistic negative influence on chronic illness. It has been argued that patients may be more likely to quit smoking and not relapse if they experience immediate positive effects such as improvement in perceived health-related quality of life (HRQoL).9,10 HRQoL is a measure of an individual’s perception of physical, mental, and social well-being11,12 and may present additional opportunities for improving smoking cessation outcomes. A large number of studies examining the relationship between smoking status and HRQoL have found that smoking cessation improves HRQoL10,11,13–16 or that nonsmokers and former smokers have better HRQoL compared to current smokers.9,16–23 This suggests that smoking status is related to HRQoL. Physical activity has been shown to improve HRQoL.24 In particular, exercise training improves HRQoL among patients with cancers,25,26 chronic obstructive pulmonary disease,27 and cardiovascular disease.28–31 Recent findings from a smoking cessation trial by Bloom and colleagues suggest that being physically active may result in incremental improvements in HRQoL among smokers who successfully quit smoking.32 In particular, exercise was associated with improved mental well-being (but not physical or overall health) after taking into account smoking status at the end of the study period.32 However, the sample size for the trial was small (N = 61) and may not have been powered to detect changes in quality of life scores. We now use data from a large national cross-sectional study to assess whether physical activity modifies the association between smoking status and HRQoL. Methods Data were extracted from the 2014 Behavioral Risk Factor Surveillance System (BRFSS) secondary dataset in 2015. BRFSS is an on-going telephone-based survey system that assesses behavioral risk factors among non-institutionalized US population aged 18 years or older. The Centers for Disease Control and Prevention developed the survey and individual state health departments have conducted the survey annually since 1984. The 2014 survey includes participants from the 50 US states, the District of Columbia, Guam, and Puerto Rico who were selected using a stratified, multistage probability sampling design, incorporating random-digit-dialing methods for data collection via both landline and cellular telephones. Approval for this study was obtained from the University of Texas at Austin Office of Research Support. Study Sample Residents of the 50 US states and the District of Columbia and those who gave definitive responses to all variables of interest were included in the present study. Residents of Guam and Puerto Rico and those who gave inexact responses (“not sure” or “don’t know”) or had missing values on any variable of interest were excluded. Measures The dependent variables were eight quality of life indicators obtained from the sections of the BRFSS on health status and healthy days (health-related quality of life) in the core module and the section on healthy days (symptoms) in the optional module. The core module is used by all state health departments without modification in wording while the optional module is optional. The indicators measured general health, physical health, mental health, activity limitations, pain, depressive symptoms, anxiety symptoms, and vitality (Supplementary Appendix Table 1). Respondents were asked to rate their general health with the following response options provided: excellent, very good, good, fair, and poor. We dichotomized the responses as either (1) excellent/very good/good or (2) fair/poor. The responses of excellent, very good, or good were deemed “high HRQoL.” For the remaining HRQoL variables, respondents were asked to provide the number of days during the past 30 days that they felt a certain way. We dichotomized the frequency into: ≥14 days and <14 days. Less than 14 days of poor physical health, poor mental health, activity limitations, pain, depressive symptoms, and anxiety symptoms were deemed “high HRQoL.” Likewise, reporting feeling full of energy for 14 or more days was deemed “high HRQoL.” The use of binary data for quality of life indicators is consistent with other studies that assessed the relationship between smoking and HRQoL using BRFSS data.9,21 Determination of smoking status was based on two self-reported questions: (1) “Have you smoked at least 100 cigarettes in your entire life?” and (2) “Do you now smoke cigarettes every day, some days, or not at all?” Respondents who had smoked <100 cigarettes in their entire life were classified as nonsmokers, those who had smoked ≥100 cigarettes in their entire life and were “now” smoking every day or some days were classified as current smokers, whereas those who had smoked ≥100 cigarettes in their entire life but were “now” not smoking at all were classified as former smokers. We also extracted demographic variables (age, race, gender, educational attainment, marital status, income, and employment status), clinical variables (healthcare coverage, comorbidity, and body mass index), and behavioral variables (alcohol use within the past 30 days, flu vaccination within the past 12 months, and physical activity within the past month). The comorbidity variable was derived from recoding the items in the section on chronic health conditions. This section was introduced with the question: “Has a doctor, nurse, or other health professional EVER told you that you had any of the following?” Respondents were classified as not having a comorbid condition if they responded “no” to the following conditions: myocardial infarction, coronary heart disease, stroke, asthma, cancer, chronic obstructive pulmonary disease, arthritis depression, kidney disease, and diabetes. Respondents were classified as having a comorbid condition if they reported having a diagnosis of any of the previously listed conditions. Respondents who reported that they had “ever” been told that they had asthma were asked the follow-up question: “Do you still have asthma?” We classified those who responded “yes” to this follow-up question as having asthma and those who responded ‘no’ as not having asthma. Female respondents who reported that they had ‘ever’ been told that they diabetes were asked the follow-up question: “Was this only when you were pregnant?” We classified those who responded that they had been told they had diabetes only during pregnancy as not having diabetes and those who had been told they had diabetes at other times as having diabetes. Statistical Analysis Demographic, clinical, and behavioral variables were summarized using frequencies and percentages. Chi-square analysis was used to determine whether there were differences among (1) nonsmokers, (2) former smokers, and (3) current smokers based on demographic, clinical, and behavioral characteristics. For each quality of life indicator, unadjusted and adjusted logistic regression models were used to assess the relationship between smoking status and HRQoL. We adjusted for demographic, clinical, and behavioral variables. We also included the smoking status by exercise interaction term to the adjusted models and evaluated whether the interaction term was significant. For all analyses, we adjusted for the complex sampling design of the survey data. Data analyses were performed using SAS version 9.4 (SAS Institute, Inc, Cary, North Carolina). To control for multiple tests, we used Bonferonni-corrected p values where p < .05 for a significant global test. Results The 2013 BRFSS included data from 464664 (weighted n = 248482532) adult respondents. After the exclusion of residents of Guam and Puerto Rico (8506) and those who gave inexact responses or had missing values on any variable of interest (123478), the final sample size for our study was 332680 (weighted n = 173278039). According to our definition of smoking status, 56.9% were nonsmokers, 25.3% were former smokers, and 17.8% were current smokers. Table 1 shows the differences between nonsmokers, former smokers, and current smokers categorized by demographic, clinical, and behavioral characteristics. Compared to nonsmokers, former smokers were more likely to be 65 years or older, White, have at least one comorbidity, report using alcohol within the past 30 days, and report receiving a flu vaccination within the past 12 months. On the other hand, current smokers were more likely to be uncoupled (divorced, widowed, separated, or never married) and earn less than $20000 and less likely to have graduated college, have health care coverage or engage in physical activity. Table 1. Differences Among Nonsmokers, Former Smokers, and Current Smokers According to Demographic, Clinical, and Lifestyle Characteristics (N = 332680; Weighted N = 173278039) Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  *Statistically significant at p < .0001. aN = 183299; Weighted n = 98617039. bN = 98346; Weighted n = 43877591. cN = 51035; Weighted n = 30783409. View Large Table 1. Differences Among Nonsmokers, Former Smokers, and Current Smokers According to Demographic, Clinical, and Lifestyle Characteristics (N = 332680; Weighted N = 173278039) Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  Characteristics  Nonsmokera % (SE)  Former smokerb % (SE)  Current smokerc % (SE)  Age (%)*   18–44  51.3 (0.2)  28.5 (0.3)  52.3 (0.4)   45–64  33.6 (0.2)  39.5 (0.3)  38.3 (0.4)   ≥65  15.1 (0.1)  32.0 (0.3)  9.4 (0.2)  Race (%)*   White  63.2 (0.2)  77.7 (0.3)  70.0 (0.4)   Black  13.0 (0.2)  7.6 (0.2)  13.0 (0.3)   Hispanic  15.3 (0.2)  9.8 (0.3)  10.8 (0.3)   Multiracial  1.2 (0.0)  1.2 (0.1)  1.8 (0.1)   Other  7.3 (0.2)  3.7 (0.2)  4.3 (0.2)  Gender (%)*   Male  45.9 (0.2)  57.7 (0.3)  55.0 (0.4)   Female  54.1 (0.2)  42.3 (0.3)  45.0 (0.4)  Educational level (%)*   Some high school or less  9.7 (0.2)  11.8 (0.3)  20.5 (0.4)   High school graduate  24.3 (0.2)  29.3 (0.3)  35.9 (0.4)   Some college/Technical school  31.1 (0.2)  33.5 (0.3)  31.9 (0.4)   College graduate  34.9 (0.2)  25.3 (0.2)  11.8 (0.2)  Marital status (%)*   Not coupled  41.6 (0.2)  35.7 (0.3)  54.9 (0.4)   Coupled  58.4 (0.2)  64.3 (0.3)  45.1 (0.4)  Income (%)*   <$20000  16.5 (0.2)  15.9 (0.2)  30.1 (0.4)   <$35000  18.3 (0.2)  20.0 (0.3)  25.2 (0.4)   <$75000  28.9 (0.2)  32.1 (0.3)  27.3 (0.4)   ≥$75000  36.3 (0.2)  32.0 (0.3)  17.4 (0.3)  Employment status (%)*   Employed  62.8 (0.2)  53.1 (0.3)  58.1 (0.4)   Unemployed  19.2 (0.2)  10.5 (0.2)  18.3 (0.3)   Retired  13.8 (0.1)  29.1 (0.3)  10.1 (0.2)   Unable to work  4.2 (0.1)  7.3 (0.2)  13.6 (0.3)  Healthcare coverage (%)*   Yes  88.5 (0.2)  91.1 (0.2)  78.5 (0.4)   No  11.5 (0.2)  8.9 (0.2)  21.5 (0.4)  Comorbidities (%)*   None  56.7 (0.2)  36.3 (0.3)  41.2 (0.4)   At least one  43.3 (0.2)  63.7 (0.3)  58.8 (0.4)  Body mass index (%)*   <18.50  1.7 (0.1)  1.1 (0.1)  2.8 (0.1)   ≥18.50 – <25.00  35.0 (0.2)  26.9 (0.3)  34.9 (0.4)   ≥25.00 – <30.00  34.9 (0.2)  38.5 (0.3)  34.1 (0.4)   ≥30.00  28.4 (0.2)  33.6 (0.3)  28.2 (0.4)  Alcohol use (%)*   Yes, within past 30 days  52.8 (0.2)  59.2 (0.3)  58.9 (0.4)   Not within past 30 days  47.2 (0.2)  40.8 (0.3)  41.1 (0.4)  Flu vaccination (%)*   Yes, within past 12 months  39.5 (0.2)  45.6 (0.3)  28.7 (0.4)   Not within past 12 months  60.5 (0.2)  54.4 (0.3)  71.3 (0.4)  Physical activity (%)*   Yes, within past month  81.0 (0.2)  77.2 (0.3)  69.5 (0.4)   Not within past month  19.0 (0.2)  22.8 (0.3)  30.5 (0.4)  *Statistically significant at p < .0001. aN = 183299; Weighted n = 98617039. bN = 98346; Weighted n = 43877591. cN = 51035; Weighted n = 30783409. View Large Table 2 shows the odds of a high HRQoL for former smokers and current smokers compared to nonsmokers. Table 3 shows the odds of having high HRQoL for those who exercise compared to those who do not. The adjusted models in Tables 2 and 3 are identical. However, different post hoc tests are represented in the tables. Overall, former smokers and current smokers had lower odds of having high HRQoL compared to nonsmokers. The odds were lower for current smokers than for former smokers. Conversely, those who exercised had higher odds of having high HRQoL compared to those who did not exercise. There were significant interactions between smoking status and physical activity on the general health, physical health, activity limitations, and depressive symptoms domains. There were smaller relative differences in the odds of a high HRQoL between former smokers and nonsmokers among those who exercised than among those who did not exercise. That is, the odds ratios for former smokers were closer to 1 among those who exercised relative to those who did not exercise (Table 2). Also, there were sharper differences in the odds of a high HRQoL between current smokers and nonsmokers among those who exercised than among those who did not exercise. That is, the odds ratios for current smokers were further away from 1 among those who exercised compared to those who did not exercise (Table 2). Similarly, there were sharper relative differences between those who exercised and those who did not exercise among former smokers than among current smokers. In other words, the odds ratios for those who exercised were further away from 1 among former smokers compared to current smokers (Table 3). Table 2. Odds of High Health-Related Quality of Life Based on Smoking Status and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  aHealth-related quality of life (HRQoL) regressed on smoking status. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by smoking status at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 2. Odds of High Health-Related Quality of Life Based on Smoking Status and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  QoL measure    Percentage with high HRQOL  Unadjusted Modela OR (95% CI)  Adjusted modelb OR (95% CI)          Exercise  No exercise  General healthcde  Nonsmoker  87.59  1  1  1  Former smoker  80.19  0.574* (0.549–0.599)  0.847* (0.796–0.901)  0.722* (0.662–0.788)  Current smoker  74.71  0.419* (0.399–0.439)  0.650* (0.602–0.701)  0.750* (0.680–0.826)  Physical healthcdf  Nonsmoker  91.49  1  1  1  Former smoker  85.84  0.564* (0.537–0.592)  0.862* (0.804–0.925)  0.733* (0.671–0.800)  Current smoker  81.84  0.419* (0.397–0.442)  0.668* (0.612–0.729)  0.775* (0.701–0.855)  Mental healthdf  Nonsmoker  91.60  1  1  1  Former smoker  89.24  0.760* (0.720–0.803)  0.817* (0.760–0.878)  0.813 (0.734–0.901)  Current smoker  78.25  0.330* (0.312–0.348)  0.525* (0.486–0.568)  0.612* (0.552–0.678)  Activity limitationscdf  Nonsmoker  94.74  1  1  1  Former smoker  90.43  0.524* (0.495–0.556)  0.745* (0.682–0.813)  0.723* (0.652–0.800)  Current smoker  85.21  0.320* (0.301–0.340)  0.545* (0.490–0.606)  0.681* (0.608–0.762)  Paindf  Nonsmoker  99.63  1  1  Former smoker  99.26  0.499* (0.406–0.614)  0.731 (0.591–0.904)  Current smoker  98.82  0.274* (0.221–0.339)  0.601* (0.471–0.768)  Depressive symptomscdf  Nonsmoker  99.73  1  1  1  Former smoker  99.62  0.724 (0.559–0.936)  1.004 (0.706–1.427)  0.863 (0.567–1.266)  Current smoker  98.90  0.247* (0.193–0.317)  0.423* (0.291–0.616)  0.847 (0.577–1.244)  Anxietydf  Nonsmoker  99.49  1  1  Former smoker  99.39  0.833 (0.676–1.027)  0.940 (0.753–1.173)  Current smoker  98.45  0.325* (0.268–0.394)  0.622* (0.498–0.776)  Vitalitydf  Nonsmoker  3.39  1  1  Former smoker  2.79  0.817* (0.746–0.896)  0.900 (0.818–0.990)  Current smoker  2.86  0.841 (0.746–0.949)  0.876 (0.772–0.995)  aHealth-related quality of life (HRQoL) regressed on smoking status. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by smoking status at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 3. Odds of High Health-Related Quality of Life Based on Physical Activity and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  aHealth-related quality of life (HRQoL) regressed on exercise. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by engagement in physical activity at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Table 3. Odds of High Health-Related Quality of Life Based on Physical Activity and Smoking Status by Physical Activity Interaction (N = 332680; Weighted N = 173278039) HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  HRQoL measure    Percentage with high HRQoL  Unadjusted model OR (95% CI)a  Adjusted model OR (95% CI)b          Nonsmoker  Former smoker  Current smoker  General health cde  No exercise  67.62  1  1  1  1  Exercise  87.88  3.472* (3.338–3.612)  1.838* (1.706–1.981)  2.157* (1.997–2.330)  1.593* (1.446–1.754)  Physical health cdf  No exercise  76.01  1  1  1  1  Exercise  91.82  3.546* (3.394–3.703)  2.026* (1.870–2.196)  2.385* (2.201–2.585)  1.748* (1.579–1.935)  Mental healthdf  No exercise  81.56  1  1  Exercise  90.63  2.185* (2.084–2.292)  1.48* (1.400–1.567)  Activity limitations cdf  No exercise  81.57  1  1  1  1  Exercise  94.88  4.191* (3.985–4.408)  2.566* (2.326–2.831)  2.645* (2.407–2.906)  2.055* (1.833–2.303)  Paindf  No exercise  98.71  1  1  Exercise  99.64  3.656* (3.071–4.352)  1.729** (1.438–2.079)  Depressive symptoms cdf  No exercise  99.15  1  1  1  1  Exercise  99.67  2.589* (2.099–3.193)  1.685 (1.160–2.449)  1.960* (1.34–2.868)  0.842 (0.601–1.180)  Anxietydf  No exercise  98.85  1  1  Exercise  99.40  1.934* (1.631–2.292)  1.205 (1.014–1.432)  Vitalitydf  No exercise  2.29  1  1  Exercise  3.38  1.491* (1.343–1.656)  1.474* (1.320–1.647)  aHealth-related quality of life (HRQoL) regressed on exercise. bHRQoL regressed on age, race, gender, educational attainment, marital status, income, employment status, healthcare coverage, comorbidity, body mass index, alcohol use, flu vaccination, physical activity, smoking status, and smoking status by physical activity interaction. cInteraction effect is significant (Bonferroni-corrected). dChi-square test show a significant difference in proportion of individuals with high HRQoL by engagement in physical activity at p <0.001 (Bonferroni-corrected). eHRQoL scores were dichotomized into high HRQoL (Excellent, Very Good, or Good) versus low HRQoL (Fair or Poor). fHRQoL scores were dichotomized into high HRQoL (those experiencing high HRQoL for 14 or more days in the past 30 days) versus low HRQoL (those experiencing high HRQoL for less than 14 days in the past 30 days). View Large Discussion Smoking cessation11,13–16 and physical activity24 have, individually, been shown to improve HRQoL. This supports our overall finding of higher HRQoL among former smokers and those who exercise relative to smokers and those who do not exercise. Our study assessed whether there is an interaction between smoking status and engagement in physical activity in their association with HRQoL. We found evidence to support this question on four quality of life domains: general health, physical health, activity limitations, and depressive symptoms. On these domains, differences in HRQoL between former smokers and nonsmokers were stronger among those who did not exercise than among those who did. This indicates that smokers who quit smoking may experience HRQoL that more closely approximates that of nonsmokers if they include physical activity in their lifestyle. This could be beneficial to former smokers, given that former smokers tend to have poorer quality of life when compared to nonsmokers.9,18,19,23 A similar argument also holds when comparing the relationship between physical activity and HRQoL by smoking status. Differences in HRQoL between those who exercised and those who did not were stronger among former smokers than among current smokers. On the four domains with significant interaction effects, former smokers who exercised had 70% to 160% higher odds of a high HRQoL than those who did not exercise (Table 3). On the other hand, the odds of a high HRQoL ranged from 20% to 110% higher for smokers who exercised relative to those who did not exercise. This implies that physical activity alone may not sufficiently improve overall well-being experienced by individuals who smoke. It is important to note that the ideal option would be not to initiate smoking since a higher proportion of nonsmokers had high HRQoL compared to former smokers on all HRQoL measures (Table 2). The study implications are particularly important for program planners who design lifestyle interventions and for health care professionals who advise and assist patients to make lifestyle changes. The findings are also important for patients with medical illness. Medical illness has been shown to motivate individuals who smoke to quit smoking.33,34 Individuals with medical illness are also more likely to make other lifestyle changes such as adopting physical activity.35 Hence, behavioral interventions that combine smoking cessation and physical activity may be more effective than either smoking cessation or physical activity alone in improving quality of life measures such as overall, physical and mental health, and degree of limitation to activities due to poor health. Additionally, health care providers can support patients who successfully quit smoking to add exercise to their daily routine with the expectation that they would experience enhanced improvement in their overall well-being. The study has several limitations. The strength of our evidence is weakened by the cross-sectional design of our study. Although the smoking cessation trial by Bloom and colleagues,32 of which our study is a replication, may have offered stronger evidence given its randomized controlled design, it also faced challenges that limited the power of the study and compromised its randomized design. We make up for some of our shortcoming by our large sample and national representativeness of the sample. However, our use of case-wise deletion of missing data may have introduced some bias as it is possible that participants excluded from the study may have been different from our final study sample. To conclude, smoking and lack of physical activity are associated with poor quality of life. Physical activity may have an additive effect in improving HRQoL among smokers who quit smoking such that their well-being tends towards that of nonsmokers. Health care providers may advise and support their patients to combine engagement in physical activity and smoking cessation or non-initiation of smoking with the aim of improving their general and physical health as well as alleviating activity limitations and depressive symptoms. Further research should include adequately powered intervention studies to validate our findings. Supplementary Material Supplementary data is available at Nicotine & Tobacco Research online Funding No financial disclosures were reported by the authors of this paper Declaration of Interests The authors have no conflicts of interest to declare. References 1. 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Nicotine and Tobacco ResearchOxford University Press

Published: Mar 15, 2018

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