Physical activity and cause-specific mortality: the Rotterdam Study

Physical activity and cause-specific mortality: the Rotterdam Study Abstract Background Physical activity (PA) is associated with lower risk for all-cause mortality. However, in elderly people, it remains unknown which types of PA are associated with mortality and whether the association between PA and mortality differs by cause of death. Methods We assessed the association of total PA, walking, cycling, domestic work, sports and gardening with all-cause mortality, and the association of total PA with cause-specific mortality, using Cox proportional hazard models among 7225 older adults (mean age: 70 years) from the prospective population-based Rotterdam Study. Deaths were classified as due to cardiovascular diseases (CVDs), cancer, infections, external causes, dementia, chronic lung diseases or other causes. Activities were categorized into tertiles (lowest tertile as reference). To account for the possibility of reverse causation, we excluded the first 5 and 10 years of follow-up. Results Over a median of 13.1 years of follow-up (interquartile range: 8.4–14.6 years), 3261 participants died. The hazard ratios (HRs) and 95% confidence intervals (95% CIs) associated with high total PA compared with low were 0.69 (0.63, 0.75), 0.69 (0.58, 0.81), 0.44 (0.27, 0.71), 0.47 (0.32, 0.71) and 0.56 (0.46, 0.69) for mortality from all causes, CVDs, chronic lung diseases, infections and other causes, respectively. With longer exclusion times, the strength of these associations was attenuated. All PA types were associated with lower all-cause mortality risk. Conclusions Engagement in higher PA levels was associated with lower risk of mortality from CVDs, chronic lung diseases, infections and other causes. Participating in any PA might reduce mortality risk in older adults. Epidemiology, cause-specific mortality, Rotterdam Study, physical activity, older adults Key Messages In older adults, it remains unknown whether cycling, walking, domestic work, gardening and sports contribute to the reduction in all-cause mortality risk. There is limited information on the association of physical activity with specific causes of death, including mortality related to dementia and chronic lung diseases. In this population-based study of older adults, we found total physical activity to be associated with a lower mortality risk related to all causes and cardiovascular diseases, chronic lung diseases, infections and other causes. All physical activity types were associated with a reduction in all-cause mortality. Public health efforts should stress engagement in any type of physical activity. Introduction Being physically active at moderate intensity at the recommended level of 150 to 300 min/week1 can reduce the all-cause mortality risk by up to 26%.2,3 However, most studies have focused on the effect of overall physical activity (PA). Thus, it remains unclear which specific PA types relate to mortality.4–7 Differences in frequency, intensity, duration and context in which one is engaged in specific PA types8,9 might lead to different associations with mortality. For older people who are unable to engage in recreational or leisure-time PA, information on the health effects of other PA types could help public health institutes create recommendations specially targeted at older adults. Recently, one study investigated the association between different PA domains and mortality among adults (aged 16–92 years) and found a beneficial association of leisure-time PA with all-cause mortality, but not with work-related PA or commuting.7 In two other studies, cycling to work4 and walking or cycling for transportation6 were associated with a lower all-cause mortality risk. The described studies were performed mostly in middle-aged adults, and less is known about what kind of activities are beneficially associated with mortality in an elderly population. This is important, since PA levels tend to decrease with age and PA types in which older adults engage differ markedly from the activities performed by younger and middle-aged adults.10 Additionally, information is lacking on whether PA is associated with specific causes of death, including mortality related to dementia and chronic lung diseases.11–13 We examined the association of PA with all-cause and cause-specific mortality in a middle-aged and elderly population. Furthermore, we assessed independent associations of walking, cycling, sports, domestic work and gardening with all-cause mortality. Methods Study population This study was embedded in the Rotterdam Study (RS), a prospective population-based cohort, among subjects aged 55 years or older in the municipality of Rotterdam, The Netherlands. The aim of the study was to examine the incidence of risk factors for neurological, cardiovascular, psychiatric and other chronic diseases. Details of the study have been published previously.14 Between 1997 and 2001, 7808 participants were invited for the research examinations and of these 7310 participants completed a PA questionnaire (Figure 1). Subsequently, 52 subjects were excluded because informed consent for follow-up data collection was withdrawn or not provided, and 33 participants were excluded due to unreliable PA data. Finally, 7225 subjects were included in the analyses. To collect baseline information, trained research assistants interviewed the participants at home. Information regarding the measurement of covariates is available as Supplementary data at IJE online. Figure 1 View largeDownload slide Flowchart of participant inclusion for the Rotterdam Study. Figure 1 View largeDownload slide Flowchart of participant inclusion for the Rotterdam Study. All subjects gave written informed consent, and the study was approved by the institutional review board (Medical Ethics Committee) of the Erasmus Medical Center and by the review board of The Netherlands Ministry of Health, Welfare and Sports. Physical activity assessment PA levels were assessed at baseline with an adapted version of the Zutphen Physical Activity Questionnaire.15 This questionnaire has been validated with a test-retest reliability of 0.93. The correlation with doubly labelled water, the gold standard for measuring PA, was 0.61.16 The original Zutphen questionnaire contains questions on walking, cycling, sports, gardening and hobbies. In the current, study questions on housekeeping activities were added, to attain a more complete assessment of PA levels. Detailed information on the collection of PA data has been described previously.17 To quantify activity intensity, we used metabolic equivalent of task (MET). We assigned MET-values to all activities mentioned in the questionnaire.18 Sports that were not in this compendium and to which no MET-value could be assigned (e.g. underwater hockey, roller skiing) were not used in the analyses (n = 33; 2.8%). Finally, we multiplied MET-values of specific activities with time (in hours) per week spent in that activity to calculate MET·h·week-1 in total PA and in every PA type (cycling, walking, sports, domestic work, gardening). Assessment of cause-specific mortality General practitioners report events of interest by means of a computerized system, or notify new events annually. Trained research assistants subsequently collected information from medical records at the general practitioners’ offices, hospitals and nursing homes. Two research physicians independently coded the events according to the International Classification of Diseases, Tenth Revision (ICD-10). Thereafter, a senior physician reviewed all coded events. Information on vital status of the participants was obtained from the clinical follow-up data collection described above and from municipal records. Coded information on cause-specific mortality was available until 1 January 2014. Cause-specific mortality was recoded according to the ICD-10 codes. We categorized the events as deaths due to cardiovascular diseases (CVDs), cancer, external causes, dementia, infections, chronic lung diseases and other causes19 (see Supplementary document, available as Supplementary data at IJE online). Statistical analysis Due to non-normal distributions, total PA, walking and domestic work were categorized into three equal-sized groups (i.e. tertiles). Since cycling, gardening and sports were not practised by more than 60% of the population, the reference category for PA levels was no participation and the remaining two categories were divided by using the median.8 Consequently, the categories of total PA, walking and domestic work were coded as low, medium and high, and the categories of cycling, gardening and sports were coded as never, medium and high. We investigated the associations of total PA and every PA type with all-cause mortality, and the association of total PA with cause-specific mortality, with Cox proportional hazard analysis, after confirming that the assumption for proportional hazards was met on the basis of Schoenfeld residuals. We adjusted our models for age, sex, smoking, alcohol consumption, education, diet quality (Dutch healthy diet index), marital status and current diseases [i.e. diabetes, CVDs, cancer and chronic obstructive pulmonary disease (COPD)]. In the analyses between PA types and all-cause mortality, we additionally adjusted for the other PA types, operationalized as [(MET·h·week-1 in total PA) minus (MET·h·week-1 from PA type under investigation)]. The decision to include confounders in the multivariable regression models was based on previous literature or a >10%-change of the effect estimate in the crude model.4,5 PA variables were entered as categorical variables (lowest tertile/no participation as reference) in the separate models. Additionally, we analysed total PA continuously per 50 MET·h·week-1 increase. The underlying time scale in all models was follow-up time, defined as the time between PA assessment and death, loss to follow-up or censoring at 1 January 2014. In sensitivity analyses, to examine the effect of body mass index (BMI) and other biological covariates, we repeated all our analyses in a model adjusted for BMI (Model 2a) and a model additionally adjusted for total and high-density lipoprotein (HDL) cholesterol, glucose, systolic blood pressure (SBP) and the use of anti-hypertensive medication (Model 2 b). We also performed sensitivity analyses with stratified models by age (below/above 65 years) and sex, including descriptive analyses comparing men and women. We investigated the possible effect of reverse causation, by excluding the first 5 and 10 years of follow-up. We also excluded adults with prevalent CVDs, COPD, cancer or diabetes at baseline, to examine the possibility that the results would be driven by adults in worse health. Moreover, 11.5% (n = 828) were employed at baseline, but we did not collect information on occupational PA. Therefore, we repeated our analyses in participants not in the active labour force. Finally, we examined the association between PA and mortality from the five most frequently occurring cancers in the current study: lung cancer, colon cancer, pancreas cancer, breast cancer and prostate cancer. Data were missing for diet quality (27.0%), HDL cholesterol (14.3%), total cholesterol (13.3%), glucose (13.3%), BMI (10.7%), SBP (10.3%) and diabetes (9.5%). Other covariates had <5% missing data. We imputed missing data using Markov Chain Monte Carlo multiple imputation (n = 5 imputations). All analyses were conducted using SPSS software version 20 (IBM SPSS Statistics for Windows, Armonk, NY: IBM Corp.) and R (3.0.1). Results Baseline characteristics of the study population are shown in Table 1, and the proportion of participants who engaged in the different PA types is shown in Supplementary Figure 1, available as Supplementary data at IJE online. Table 1 Baseline participant characteristics by tertile of total physical activity Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Numbers are mean (SD), unless otherwise stated. Table 1 Baseline participant characteristics by tertile of total physical activity Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Numbers are mean (SD), unless otherwise stated. During 15 years of follow-up (median: 13.1 years, interquartile range: 8.4–14.6 years), 3261 participants died. The number of participants and the number of events in each group of every PA type are presented in Supplementary Table 1, available as Supplementary data at IJE online. A description and frequency of each cause of death in the total population are presented in Table 2. Table 2 Description and frequencies of cause-specific mortality for participants in the Rotterdam Study Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Table 2 Description and frequencies of cause-specific mortality for participants in the Rotterdam Study Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) All-cause mortality In the categorical analysis, high compared with low total PA was associated with a 31% lower risk of all-cause mortality (95% CI: 0.63, 0.75) (Figure 2). Additionally, all PA types were associated with a reduction in all-cause mortality (Table 3). Each 50 MET·h·week-1 increment of total PA, equivalent to an average 105 min/day of PA of 4 METs, was associated with a 19% lower mortality risk (95% CI: 0.78, 0.85) (Figure 2). Table 3 Association of physical activity types with all-cause mortality HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) The models were adjusted for age, sex, smoking, alcohol consumption, education, marital status, diet quality, current CVD, current cancer, current diabetes, chronic obstructive pulmonary disease and the other physical activity types. The icons at the top represent walking, cycling, domestic work, gardening and sports, from left to right. a For cycling, gardening and sports, the low category refers to not doing that particular activity. Walking is equivalent to 3.0 METs. The median levels of walking across categories are therefore equivalent respectively to 24, 60 and 141 min per day of walking. Average domestic work is equivalent to 3.5 METs.18 The median levels of domestic work across categories are therefore equivalent to 28, 83 and 142 min per day of domestic work. Cycling is equivalent to 4.0 METs. The median levels of cycling across categories are therefore equivalent to 0, 13 and 51 min per day of cycling. Gardening is equivalent to 4.0 METs. The median levels of gardening across categories are therefore equivalent to 0, 9 and 30 min per day of gardening. Average sports is equivalent to 5.5 METs. The median levels of sports across categories are therefore equivalent to 0, 8 and 30 min per day of sports. Table 3 Association of physical activity types with all-cause mortality HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) The models were adjusted for age, sex, smoking, alcohol consumption, education, marital status, diet quality, current CVD, current cancer, current diabetes, chronic obstructive pulmonary disease and the other physical activity types. The icons at the top represent walking, cycling, domestic work, gardening and sports, from left to right. a For cycling, gardening and sports, the low category refers to not doing that particular activity. Walking is equivalent to 3.0 METs. The median levels of walking across categories are therefore equivalent respectively to 24, 60 and 141 min per day of walking. Average domestic work is equivalent to 3.5 METs.18 The median levels of domestic work across categories are therefore equivalent to 28, 83 and 142 min per day of domestic work. Cycling is equivalent to 4.0 METs. The median levels of cycling across categories are therefore equivalent to 0, 13 and 51 min per day of cycling. Gardening is equivalent to 4.0 METs. The median levels of gardening across categories are therefore equivalent to 0, 9 and 30 min per day of gardening. Average sports is equivalent to 5.5 METs. The median levels of sports across categories are therefore equivalent to 0, 8 and 30 min per day of sports. Figure 2 View largeDownload slide Association of total physical activity in tertiles with overall and cause-specific mortality among participants in the Rotterdam Study, 1997–2014. For every medium and high group, the reference is the low category. The models were adjusted for age, sex, smoking, alcohol consumption, education, current CVD, current cancer, current diabetes and current chronic obstructive pulmonary disease. Total PA is composed of all PA types and thus of different METs. In this regard, the median levels of total PA across categories are equivalent to 1.4, 2.7 and 4.4 h per day of moderate PA equivalent of 4 METs. Figure 2 View largeDownload slide Association of total physical activity in tertiles with overall and cause-specific mortality among participants in the Rotterdam Study, 1997–2014. For every medium and high group, the reference is the low category. The models were adjusted for age, sex, smoking, alcohol consumption, education, current CVD, current cancer, current diabetes and current chronic obstructive pulmonary disease. Total PA is composed of all PA types and thus of different METs. In this regard, the median levels of total PA across categories are equivalent to 1.4, 2.7 and 4.4 h per day of moderate PA equivalent of 4 METs. Cause-specific mortality Higher levels of total PA were associated with lower risk of mortality from CVDs, chronic lung diseases, infections and death from other causes. Each 50 MET·h·week-1 more of total PA was associated with up to 39% lower risk of mortality from CVDs, chronic lung diseases, other causes and infections (Figure 2). Sensitivity analyses Supplementary Tables 2 and 3, available as Supplementary data at IJE online, show the results from all sensitivity analyses of PA types with all-cause mortality, and total PA with cause-specific mortality, respectively. Additional adjustment for BMI in Model 2a and for other biological risk factors in Model 2 b slightly attenuated the associations. In the descriptive analyses stratified by sex, we observed that the mean level of total PA was higher in women than in men, and that domestic work was on average higher in women at 46.2 [standard deviation (SD): 21.3] MET·h·week-1 compared with men at 21.2 (SD: 17.7) MET·h·week-1 (Supplementary Table 4, available as Supplementary data at IJE online). The association between domestic work and all-cause mortality seems to be driven by women. After excluding the first 5 years of follow-up, our results did not materially change. After excluding the first 10 years of follow-up, the associations were attenuated. Noteworthy, we observed a reduction in the strength of the association between total PA and cause-specific mortality with longer exclusion times (Supplementary Figure 2, available as Supplementary data at IJE online). The association in participants without current chronic disease were similar to the main results. Excluding participants in the active labour force did not materially change the effect estimates. In our sensitivity analysis stratified by age, we observed that the associations were stronger in adults aged >65 years. The analyses in cancer-specific mortality did not show any associations (Supplementary Table 5, available as Supplementary data at IJE online). Discussion In this population-based study of older adults aged 55 and over, total PA was associated with a lower risk of mortality due to all causes, CVDs, chronic lung diseases, infections and other causes. In contrast, we did not observe an association of total PA with mortality from cancer, dementia or external causes. All five PA types were associated with a lower risk of all-cause mortality. Our findings underline that engagement in any PA type may be conducive to reducing mortality risk in older adults. Existing literature on cause-specific mortality mostly focused on CVD and cancer mortality.4–6,20,21 Our finding that higher levels of total PA are associated with lower risk of CVD mortality is in agreement with these studies. However, the fact that we did not observe an association with cancer mortality is in contrast to most previous evidence indicating a protective effect from higher PA levels.5,20,22–24 The association between PA and cancer might depend on the cancer site25,26 and it has been suggested that the association between PA and cancer occurs at least 10 years after the activity has been undertaken.6 However, in additional analyses stratifying by the five most frequently occurring cancers in the current study, and in analyses excluding the first 10 years of follow-up, we still observed no association between PA and cancer mortality. The small number of events in the cancer-specific analyses might have led to limited power to detect an association, and the results do suggest a positive association between PA and cancer, which is similar across cancer sites. Future studies with larger sample sizes should further evaluate these associations. There is a paucity of studies regarding mortality related to external causes, dementia, infections and chronic lung diseases. Our finding that PA is associated with reduced mortality related to chronic lung diseases is in agreement with some studies on respiratory disease.12,13,27 The mechanism for the potential beneficial effects of regular PA are unknown, although improved muscle function, exercise capacity and reduced inflammation can be on the causal pathway.12 Although we adjusted for prevalent COPD, our finding might still be related to reversed causality, as participants with undiagnosed lung disease might not be capable of engaging in high levels of PA to begin with. Future studies with careful adjustments should be performed to examine whether higher levels of PA truly decrease the risk for lung disease mortality. In our population, engaging in a median of 13 min/day of cycling (the medium category) was associated with a 28% lower all-cause mortality risk, which is in line with recent evidence that any PA is better than none.28 The mortality risk associated with cycling has been studied before, but conflicting results have been found. Several studies found that cycling to work,4 cycling for commuting20 or cycling for sports21 was associated with lower risk of mortality. In contrast, no association between cycling or walking for transportation and all-cause mortality6 was found among British adults. The way in which cycling was operationalized (commuting to work, any commuting, cycling for sports or all cycling) might contribute to the different findings. Moreover, the age of the participants and the cycling prevalence differed between studies. In studies including younger participants, the lower number of cases might have led to insufficient power to detect an association and in contrast to the UK, cycling is a common method of transportation in The Netherlands, where our study was performed. Domestic work is an important contributor to daily PA, especially in the elderly,10 and was associated with a lower all-cause mortality risk. The associations seemed to be driven by the women in our study, who engaged in domestic work more often than men. Our results are in line with previous studies, observing a lower all-cause mortality risk related to light household activity (<3 METS)5 and activities around the house, including gardening and do-it-yourself activities.6 However, in another study, housework was not associated with all-cause mortality in 50–64-year-old individuals.29 The differences between the studies might be related to the age group studied. This is supported by our analyses in adults <65 years, among whom we found weaker associations between domestic work and mortality. The inverse relation between domestic work and mortality independent of other PA types is consistent with the recommendations emphasizing the importance of moderate-to-vigorous intensity PA performed as part of daily living. We acknowledge that our study has several limitations. It may be hypothesized that people in poor health participate in PA less than others, creating the possibility for reverse causation. After repeating our analyses in participants without prevalent chronic disease, we observed comparable estimates, suggesting that underlying disease did not affect our associations. In contrast, in the analyses excluding the first 5 and 10 years of follow-up, the strength of the association between total PA and cause-specific mortality was attenuated with longer exclusion times. This indicates that we cannot rule out the possibility of reverse causation affecting our results. Additionally, the attenuation of the association observed with increasing exclusion times might be the result of increasing exposure misclassification, as the time span between exposure and outcome classification increases. In the current study, we only measured PA at baseline, which can cause misclassification of PA over time, since PA levels among adults tend to decline with age.30 Due to the prospective design, this misclassification is likely to be non-differential. However, future studies with repeated PA measurements are needed to investigate the effect of exposure misclassification on the association between PA and mortality. Furthermore, we collected no information about occupational PA, so we could not adjust for this in our main analyses. However, excluding participants in the active labour force (n = 828, 11.5%) in our sensitivity analyses revealed comparable estimates. Additionally, our results are based on self-reported PA. Although our questionnaire has shown to be valid and reliable,16 potential recall bias and social desirability cannot be excluded. This limitation could have resulted in bias either towards or away from the null hypothesis. Finally, our questionnaire did not distinguish between walking and cycling for sports or for means of transportation. Since the intensity might differ between sports and transportation,18 future studies are needed to examine the association of the two distinct forms with mortality. Major strengths of the current study are its prospective population-based design, large sample size of adults aged over 55, relatively long follow-up period and inclusion of seven different causes of death. Furthermore, we adjusted for several factors, thereby minimizing the possibility of the observed associations being explained by confounding. In addition, we included a number of different activities while adjusting for the remaining activities, which enabled us to examine their independent associations with all-cause mortality. In summary, in this population of older and elderly adults, we found that PA was associated with a lower risk of mortality from all causes, CVDs, chronic lung diseases, infections and other causes. All the five PA types under investigation contributed to the reduction in the all-cause mortality risk. For public health recommendations, our findings underline that engagement in any type of PA may successfully reduce mortality risk in older adults. Adults incapable of engaging in sports or exercise can engage in any activity that they enjoy and that their health allows them to, including cycling, walking and activities in and around the house. Supplementary Data Supplementary data are available at IJE online. Funding The Rotterdam Study is funded by: Erasmus MC and Erasmus University, Rotterdam, The Netherlands; the Netherlands Organisation for Scientific Research (NWO); the Netherlands Organisation for the Health Research and Development (ZonMw); the Research Institute for Diseases in the Elderly (RIDE); the Ministry of Education, Culture and Science; the Ministry for Health, Welfare and Sports; the European Commission (DG XII); and the Municipality of Rotterdam. O.H.F. works in ErasmusAGE, a centre for ageing research across the life course, funded by Nestlé Nutrition (Nestec Ltd) and Metagenic. Nestlé Nutrition (Nested Ltd) and Metagenics Inc. had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; or preparation, review and approval of the manuscript. L.L. is a Postdoctoral Fellow of the Research Foundation - Flanders (FWO). The work of H.T. was supported by a Netherlands Organisation for Scientific Research grant (017.106.370). Acknowledgements The authors gratefully acknowledge the study participants, the staff from the Rotterdam Study and the participating general practitioners and pharmacists of the Ommoord district. Additionally, we thank Meghan Murphy for carefully editing our manuscript. Author Contributions C.M.K., K.D., J.D.S., L.L., F.J.A.vR., M.A.I., G.B., H.T. and O.H.F. participated actively in each of the following aspects for this article: concep and design or analysis and interpretation of data; drafting the article or revising it critically for important intellectual content; and final approval of the version to be published. Conflict of interest: The authors declare that there is no conflict of interests regarding the publication of the paper. References 1 Physical Activity Guidelines Advisory Committee . Physical Activity Guidelines Advisory Committee Report, 2008 . Washington, DC : U.S Department of Health and Human Services , 2008 . 2 Arem H , Moore SC , Patel A et al. Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship . JAMA Intern Med 2015 ; 175 : 959 – 67 . Google Scholar CrossRef Search ADS PubMed 3 Samitz G , Egger M , Zwahlen M. Domains of physical activity and all-cause mortality: systematic review and dose-response meta-analysis of cohort studies . Int J Epidemiol 2011 ; 40 : 1382 – 400 . Google Scholar CrossRef Search ADS PubMed 4 Andersen LB , Schnohr P , Schroll M , Hein HO. All-cause mortality associated with physical activity during leisure time, work, sports, and cycling to work . Arch Intern Med 2000 ; 160 : 1621 – 28 . Google Scholar CrossRef Search ADS PubMed 5 Autenrieth CS , Baumert J , Baumeister SE et al. Association between domains of physical activity and all-cause, cardiovascular and cancer mortality . Eur J Epidemiol 2011 ; 26 : 91 – 99 . Google Scholar CrossRef Search ADS PubMed 6 Besson H , Ekelund U , Brage S et al. Relationship between subdomains of total physical activity and mortality . Med Sci Sports Exerc 2008 ; 40 : 1909 – 15 . Google Scholar CrossRef Search ADS PubMed 7 Wanner M , Tarnutzer S , Martin BW et al. Impact of different domains of physical activity on cause-specific mortality: a longitudinal study . Prev Med 2014 ; 62 : 89 – 95 . Google Scholar CrossRef Search ADS PubMed 8 Sabia S , Dugravot A , Kivimaki M , Brunner E , Shipley MJ , Singh-Manoux A. Effect of intensity and type of physical activity on mortality: results from the Whitehall II cohort study . Am J Public Health 2012 ; 102 : 698 – 704 . Google Scholar CrossRef Search ADS PubMed 9 Holtermann A , Marott JL , Gyntelberg F et al. Occupational and leisure time physical activity: risk of all-cause mortality and myocardial infarction in the Copenhagen City Heart Study. A prospective cohort study . BMJ Open 2012 ; 2 : e000556 . Google Scholar CrossRef Search ADS PubMed 10 Dong L , Block G , Mandel S. Activities contributing to total energy expenditure in the United States: results from the NHAPS Study . Int J Behav Nutr Phys Act 2004 ; 1 : 4 . Google Scholar CrossRef Search ADS PubMed 11 Rosness TA , Strand BH , Bergem AL , Engedal K , Bjertness E. Associations between physical activity in old age and dementia-related mortality: a population-based cohort study . Dement Geriatr Cogn Disord Extra 2014 ; 4 : 410 – 18 . Google Scholar CrossRef Search ADS 12 Garcia‐Aymerich J , Lange P , Benet M , Schnohr P , Antó JM. Regular physical activity reduces hospital admission and mortality in chronic obstructive pulmonary disease: a population based cohort study . Thorax 2006 ; 61 : 772 – 78 . Google Scholar CrossRef Search ADS PubMed 13 Kopperstad O , Skogen JC , Sivertsen B , Tell GS , Saether SM. Physical activity is independently associated with reduced mortality: 15-years follow-up of the Hordaland Health Study (HUSK) . PLoS One 2017 ; 12 : e0172932 . Google Scholar CrossRef Search ADS PubMed 14 Ikram MA , Brusselle GGO , Murad SD et al. The Rotterdam Study: 2018 update on objectives, design and main results . Eur J Epidemiol 2017 ; 32 : 807 – 50 . Google Scholar CrossRef Search ADS PubMed 15 Caspersen CJ , Bloemberg BP , Saris WH , Merritt RK , Kromhout D. The prevalence of selected physical activities and their relation with coronary heart disease risk factors in elderly men: the Zutphen Study, 1985 . Am J Epidemiol 1991 ; 133 : 1078 – 92 . Google Scholar CrossRef Search ADS PubMed 16 Westerterp K , Saris W , Bloemberg B , Kempen K , Caspersen C , Kromhout D. Validation of the Zutphen physical activity questionnaire for the elderly with doubly labeled water [abstract] . Med Sci Sports Exerc 1992 ; 24 : S68 . Google Scholar CrossRef Search ADS 17 Koolhaas CM , Dhana K , Golubic R et al. Physical activity types and coronary heart disease risk in middle-aged and elderly persons: the Rotterdam Study . Am J Epidemiol 2016 ; 183 : 729 – 38 . Google Scholar CrossRef Search ADS PubMed 18 Ainsworth BE , Haskell WL , Herrmann SD et al. 2011 compendium of physical activities: a second update of codes and MET values . Med Sci Sports Exerc 2011 ; 43 : 1575 – 81 . Google Scholar CrossRef Search ADS PubMed 19 Campos-Obando N , Castano-Betancourt MC , Oei L et al. Bone mineral density and chronic lung disease mortality: the Rotterdam Study . J Clin Endocrinol Metab 2014 ; 99 : 1834 – 42 . Google Scholar CrossRef Search ADS PubMed 20 Celis-Morales CA , Lyall DM , Welsh P et al. Association between active commuting and incident cardiovascular disease, cancer, and mortality: prospective cohort study . BMJ 2017 ; 357 : j1456 . Google Scholar CrossRef Search ADS PubMed 21 Oja P , Kelly P , Pedisic Z et al. Associations of specific types of sports and exercise with all-cause and cardiovascular-disease mortality: a cohort study of 80 306 British adults . Br J Sports Med 2017 ; 51 : 812 – 17 . Google Scholar CrossRef Search ADS PubMed 22 Leening MJ , Kavousi M , Heeringa J et al. Methods of data collection and definitions of cardiac outcomes in the Rotterdam Study . Eur J Epidemiol 2012 ; 27 : 173 – 85 . Google Scholar CrossRef Search ADS PubMed 23 Keum N , Bao Y , Smith-Warner SA et al. Association of physical activity by type and intensity with digestive system cancer risk . JAMA Oncol 2016 ; 2 : 1146 – 53 . Google Scholar CrossRef Search ADS PubMed 24 Kyu HH , Bachman VF , Alexander LT et al. Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013 . BMJ 2016 ; 354 : i3857. Google Scholar CrossRef Search ADS PubMed 25 Clague J , Bernstein L. Physical activity and cancer . Curr Oncol Rep 2012 ; 14 : 550 – 58 . Google Scholar CrossRef Search ADS PubMed 26 Li Y , Gu M , Jing F et al. Association between physical activity and all cancer mortality: dose-response meta-analysis of cohort studies . Int J Cancer 2016 ; 138 : 818 – 32 . Google Scholar CrossRef Search ADS PubMed 27 Andersen ZJ , de Nazelle A , Mendez MA et al. A study of the combined effects of physical activity and air pollution on mortality in elderly urban residents: the Danish Diet, Cancer, and Health Cohort . Environ Health Perspect 2015 ; 123 : 557 – 63 . Google Scholar PubMed 28 Hupin D , Roche F , Gremeaux V et al. Even a low-dose of moderate-to-vigorous physical activity reduces mortality by 22% in adults aged ≥60 years: a systematic review and meta-analysis . Br J Sports Med 2015 ; 49 : 1262 – 67 . Google Scholar CrossRef Search ADS PubMed 29 Johnsen NF , Ekblond A , Thomsen BL , Overvad K , Tjonneland A. Leisure time physical activity and mortality . Epidemiology 2013 ; 24 : 717 – 25 . Google Scholar CrossRef Search ADS PubMed 30 Päivi M , Mirja H , Terttu P. Changes in physical activity involvement and attitude to physical activity in a 16-year follow-up study among the elderly . J Aging Res 2010 ; 2010 : 174290 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Epidemiology Oxford University Press

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Abstract

Abstract Background Physical activity (PA) is associated with lower risk for all-cause mortality. However, in elderly people, it remains unknown which types of PA are associated with mortality and whether the association between PA and mortality differs by cause of death. Methods We assessed the association of total PA, walking, cycling, domestic work, sports and gardening with all-cause mortality, and the association of total PA with cause-specific mortality, using Cox proportional hazard models among 7225 older adults (mean age: 70 years) from the prospective population-based Rotterdam Study. Deaths were classified as due to cardiovascular diseases (CVDs), cancer, infections, external causes, dementia, chronic lung diseases or other causes. Activities were categorized into tertiles (lowest tertile as reference). To account for the possibility of reverse causation, we excluded the first 5 and 10 years of follow-up. Results Over a median of 13.1 years of follow-up (interquartile range: 8.4–14.6 years), 3261 participants died. The hazard ratios (HRs) and 95% confidence intervals (95% CIs) associated with high total PA compared with low were 0.69 (0.63, 0.75), 0.69 (0.58, 0.81), 0.44 (0.27, 0.71), 0.47 (0.32, 0.71) and 0.56 (0.46, 0.69) for mortality from all causes, CVDs, chronic lung diseases, infections and other causes, respectively. With longer exclusion times, the strength of these associations was attenuated. All PA types were associated with lower all-cause mortality risk. Conclusions Engagement in higher PA levels was associated with lower risk of mortality from CVDs, chronic lung diseases, infections and other causes. Participating in any PA might reduce mortality risk in older adults. Epidemiology, cause-specific mortality, Rotterdam Study, physical activity, older adults Key Messages In older adults, it remains unknown whether cycling, walking, domestic work, gardening and sports contribute to the reduction in all-cause mortality risk. There is limited information on the association of physical activity with specific causes of death, including mortality related to dementia and chronic lung diseases. In this population-based study of older adults, we found total physical activity to be associated with a lower mortality risk related to all causes and cardiovascular diseases, chronic lung diseases, infections and other causes. All physical activity types were associated with a reduction in all-cause mortality. Public health efforts should stress engagement in any type of physical activity. Introduction Being physically active at moderate intensity at the recommended level of 150 to 300 min/week1 can reduce the all-cause mortality risk by up to 26%.2,3 However, most studies have focused on the effect of overall physical activity (PA). Thus, it remains unclear which specific PA types relate to mortality.4–7 Differences in frequency, intensity, duration and context in which one is engaged in specific PA types8,9 might lead to different associations with mortality. For older people who are unable to engage in recreational or leisure-time PA, information on the health effects of other PA types could help public health institutes create recommendations specially targeted at older adults. Recently, one study investigated the association between different PA domains and mortality among adults (aged 16–92 years) and found a beneficial association of leisure-time PA with all-cause mortality, but not with work-related PA or commuting.7 In two other studies, cycling to work4 and walking or cycling for transportation6 were associated with a lower all-cause mortality risk. The described studies were performed mostly in middle-aged adults, and less is known about what kind of activities are beneficially associated with mortality in an elderly population. This is important, since PA levels tend to decrease with age and PA types in which older adults engage differ markedly from the activities performed by younger and middle-aged adults.10 Additionally, information is lacking on whether PA is associated with specific causes of death, including mortality related to dementia and chronic lung diseases.11–13 We examined the association of PA with all-cause and cause-specific mortality in a middle-aged and elderly population. Furthermore, we assessed independent associations of walking, cycling, sports, domestic work and gardening with all-cause mortality. Methods Study population This study was embedded in the Rotterdam Study (RS), a prospective population-based cohort, among subjects aged 55 years or older in the municipality of Rotterdam, The Netherlands. The aim of the study was to examine the incidence of risk factors for neurological, cardiovascular, psychiatric and other chronic diseases. Details of the study have been published previously.14 Between 1997 and 2001, 7808 participants were invited for the research examinations and of these 7310 participants completed a PA questionnaire (Figure 1). Subsequently, 52 subjects were excluded because informed consent for follow-up data collection was withdrawn or not provided, and 33 participants were excluded due to unreliable PA data. Finally, 7225 subjects were included in the analyses. To collect baseline information, trained research assistants interviewed the participants at home. Information regarding the measurement of covariates is available as Supplementary data at IJE online. Figure 1 View largeDownload slide Flowchart of participant inclusion for the Rotterdam Study. Figure 1 View largeDownload slide Flowchart of participant inclusion for the Rotterdam Study. All subjects gave written informed consent, and the study was approved by the institutional review board (Medical Ethics Committee) of the Erasmus Medical Center and by the review board of The Netherlands Ministry of Health, Welfare and Sports. Physical activity assessment PA levels were assessed at baseline with an adapted version of the Zutphen Physical Activity Questionnaire.15 This questionnaire has been validated with a test-retest reliability of 0.93. The correlation with doubly labelled water, the gold standard for measuring PA, was 0.61.16 The original Zutphen questionnaire contains questions on walking, cycling, sports, gardening and hobbies. In the current, study questions on housekeeping activities were added, to attain a more complete assessment of PA levels. Detailed information on the collection of PA data has been described previously.17 To quantify activity intensity, we used metabolic equivalent of task (MET). We assigned MET-values to all activities mentioned in the questionnaire.18 Sports that were not in this compendium and to which no MET-value could be assigned (e.g. underwater hockey, roller skiing) were not used in the analyses (n = 33; 2.8%). Finally, we multiplied MET-values of specific activities with time (in hours) per week spent in that activity to calculate MET·h·week-1 in total PA and in every PA type (cycling, walking, sports, domestic work, gardening). Assessment of cause-specific mortality General practitioners report events of interest by means of a computerized system, or notify new events annually. Trained research assistants subsequently collected information from medical records at the general practitioners’ offices, hospitals and nursing homes. Two research physicians independently coded the events according to the International Classification of Diseases, Tenth Revision (ICD-10). Thereafter, a senior physician reviewed all coded events. Information on vital status of the participants was obtained from the clinical follow-up data collection described above and from municipal records. Coded information on cause-specific mortality was available until 1 January 2014. Cause-specific mortality was recoded according to the ICD-10 codes. We categorized the events as deaths due to cardiovascular diseases (CVDs), cancer, external causes, dementia, infections, chronic lung diseases and other causes19 (see Supplementary document, available as Supplementary data at IJE online). Statistical analysis Due to non-normal distributions, total PA, walking and domestic work were categorized into three equal-sized groups (i.e. tertiles). Since cycling, gardening and sports were not practised by more than 60% of the population, the reference category for PA levels was no participation and the remaining two categories were divided by using the median.8 Consequently, the categories of total PA, walking and domestic work were coded as low, medium and high, and the categories of cycling, gardening and sports were coded as never, medium and high. We investigated the associations of total PA and every PA type with all-cause mortality, and the association of total PA with cause-specific mortality, with Cox proportional hazard analysis, after confirming that the assumption for proportional hazards was met on the basis of Schoenfeld residuals. We adjusted our models for age, sex, smoking, alcohol consumption, education, diet quality (Dutch healthy diet index), marital status and current diseases [i.e. diabetes, CVDs, cancer and chronic obstructive pulmonary disease (COPD)]. In the analyses between PA types and all-cause mortality, we additionally adjusted for the other PA types, operationalized as [(MET·h·week-1 in total PA) minus (MET·h·week-1 from PA type under investigation)]. The decision to include confounders in the multivariable regression models was based on previous literature or a >10%-change of the effect estimate in the crude model.4,5 PA variables were entered as categorical variables (lowest tertile/no participation as reference) in the separate models. Additionally, we analysed total PA continuously per 50 MET·h·week-1 increase. The underlying time scale in all models was follow-up time, defined as the time between PA assessment and death, loss to follow-up or censoring at 1 January 2014. In sensitivity analyses, to examine the effect of body mass index (BMI) and other biological covariates, we repeated all our analyses in a model adjusted for BMI (Model 2a) and a model additionally adjusted for total and high-density lipoprotein (HDL) cholesterol, glucose, systolic blood pressure (SBP) and the use of anti-hypertensive medication (Model 2 b). We also performed sensitivity analyses with stratified models by age (below/above 65 years) and sex, including descriptive analyses comparing men and women. We investigated the possible effect of reverse causation, by excluding the first 5 and 10 years of follow-up. We also excluded adults with prevalent CVDs, COPD, cancer or diabetes at baseline, to examine the possibility that the results would be driven by adults in worse health. Moreover, 11.5% (n = 828) were employed at baseline, but we did not collect information on occupational PA. Therefore, we repeated our analyses in participants not in the active labour force. Finally, we examined the association between PA and mortality from the five most frequently occurring cancers in the current study: lung cancer, colon cancer, pancreas cancer, breast cancer and prostate cancer. Data were missing for diet quality (27.0%), HDL cholesterol (14.3%), total cholesterol (13.3%), glucose (13.3%), BMI (10.7%), SBP (10.3%) and diabetes (9.5%). Other covariates had <5% missing data. We imputed missing data using Markov Chain Monte Carlo multiple imputation (n = 5 imputations). All analyses were conducted using SPSS software version 20 (IBM SPSS Statistics for Windows, Armonk, NY: IBM Corp.) and R (3.0.1). Results Baseline characteristics of the study population are shown in Table 1, and the proportion of participants who engaged in the different PA types is shown in Supplementary Figure 1, available as Supplementary data at IJE online. Table 1 Baseline participant characteristics by tertile of total physical activity Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Numbers are mean (SD), unless otherwise stated. Table 1 Baseline participant characteristics by tertile of total physical activity Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Tertiles of total PA Low Medium High Total PA, MET·h·week-1, median (range) 38.5 (<57.6) 74.3 (57.6-94.0) 123.1 (≥94.0) Participants, no (%) 2401 (33.0) 2421 (34.0) 2403 (33.0) Female, no. (%) 1045 (43.5) 1506 (62.2) 1643 (68.4) Age, years 72.7 (9.8) 69.5 (7.9) 68.0 (7.2) Educational level  Primary education, no. (%) 387 (16.1) 328 (13.5) 356 (14.8)  Lower education, no. (%) 901 (37.5) 1109 (45.8) 1118 (46.5)  Intermediate education, no. (%) 738 (30.7) 690 (28.5) 690 (28.7)  Higher education, no. (%) 375 (15.6) 294 (12.1) 239 (9.9) Living with partner, no. (%) 1409 (58.7) 1525 (63.0) 1590 (66.2) Employed, no. (%) 399 (16.6) 252 (10.4) 177 (7.4) Smoking  Never, no. (%) 991 (41.3) 1150 (47.5) 1137 (47.3)  Former, no. (%) 1048 (43.6) 983 (40.6) 968 (40.3)  Current, no. (%) 362 (15.1) 288 (11.9) 298 (12.4) Dutch Healthy Diet Index 47.0 (10.6) 48.9 (11.2) 49.3 (11.1) Alcohol, glasses/day 1.1 (1.5) 1.0 (1.5) 1.0 (1.3) BMI, kg/m2 27.3 (4.1) 27.2 (4.1) 26.8 (3.8) Disabled, no. (%) 1167 (48.6) 778 (32.1) 572 (23.8) Diabetes, no. (%) 482 (20.1) 365 (15.1) 377 (15.7) Current cancer, no. (%) 290 (12.1) 261 (10.8) 213 (8.9) Current CVD, no. (%) 561 (23.4) 308 (12.7) 252 (10.5) Current COPD, no. (%) 225 (9.4) 173 (7.1) 130 (5.4) Walking, MET·h·week-1 12.3 (9.2) 22.9 (13.6) 46.9 (29.7) Cycling, MET·h·week-1 2.6 (5.3) 7.7 (10.0) 15.1 (17.3) Domestic work, MET·h·week-1 17.9 (12.4) 36.9 (16.6) 52.3 (24.9) Gardening, MET·h·week-1 1.4 (3.6) 3.2 (7.0) 6.6 (13.3) Sports, MET·h·week-1 2.0 (5.1) 4.2 (8.5) 9.9 (18.1) Systolic blood pressure, mmHg 145.6 (21.6) 144.1 (22.1) 142.0 (21.1) Cholesterol, mmol/l 5.7 (1.0) 5.8 (0.9) 5.9 (1.0) HDL-cholesterol, mmol/l 1.3 (0.4) 1.4 (0.4) 1.4 (0.4) Glucose, mmol/l 6.2 (1.7) 6.0 (1.6) 5.8 (1.2) Numbers are mean (SD), unless otherwise stated. During 15 years of follow-up (median: 13.1 years, interquartile range: 8.4–14.6 years), 3261 participants died. The number of participants and the number of events in each group of every PA type are presented in Supplementary Table 1, available as Supplementary data at IJE online. A description and frequency of each cause of death in the total population are presented in Table 2. Table 2 Description and frequencies of cause-specific mortality for participants in the Rotterdam Study Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Table 2 Description and frequencies of cause-specific mortality for participants in the Rotterdam Study Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) Cause Description Number (%) of deaths CVD Cardio- and cerebrovascular pathology 981 (30.1) Cancer All cancer-related mortality 843 (25.9) Chronic lung disease COPD, respiratory failure 124 (3.8) Dementia Dementia as final cause of death 339 (10.4) Other causes Unspecified, unattended and sudden death, non-tumoural renal, gastrointestinal, haematological and cerebral diseases, cachexia and senility 662 (20.3) Infectious All infection-related mortality 187 (5.7) External causes Fractures, accidents and suicides 117 (3.6) Missing Cases without ICD-10 codes 8 (0.2) All-cause mortality In the categorical analysis, high compared with low total PA was associated with a 31% lower risk of all-cause mortality (95% CI: 0.63, 0.75) (Figure 2). Additionally, all PA types were associated with a reduction in all-cause mortality (Table 3). Each 50 MET·h·week-1 increment of total PA, equivalent to an average 105 min/day of PA of 4 METs, was associated with a 19% lower mortality risk (95% CI: 0.78, 0.85) (Figure 2). Table 3 Association of physical activity types with all-cause mortality HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) The models were adjusted for age, sex, smoking, alcohol consumption, education, marital status, diet quality, current CVD, current cancer, current diabetes, chronic obstructive pulmonary disease and the other physical activity types. The icons at the top represent walking, cycling, domestic work, gardening and sports, from left to right. a For cycling, gardening and sports, the low category refers to not doing that particular activity. Walking is equivalent to 3.0 METs. The median levels of walking across categories are therefore equivalent respectively to 24, 60 and 141 min per day of walking. Average domestic work is equivalent to 3.5 METs.18 The median levels of domestic work across categories are therefore equivalent to 28, 83 and 142 min per day of domestic work. Cycling is equivalent to 4.0 METs. The median levels of cycling across categories are therefore equivalent to 0, 13 and 51 min per day of cycling. Gardening is equivalent to 4.0 METs. The median levels of gardening across categories are therefore equivalent to 0, 9 and 30 min per day of gardening. Average sports is equivalent to 5.5 METs. The median levels of sports across categories are therefore equivalent to 0, 8 and 30 min per day of sports. Table 3 Association of physical activity types with all-cause mortality HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI) Lowa 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] 1.00 [ref] Medium 0.82 (0.75, 0.89) 0.72 (0.66, 0.79) 0.86 (0.79, 0.94) 0.75 (0.68, 0.83) 0.84 (0.76, 0.93) High 0.89 (0.81, 0.97) 0.65 (0.58, 0.72) 0.77 (0.70, 0.86) 0.86 (0.77, 0.96) 0.81 (0.73, 0.91) The models were adjusted for age, sex, smoking, alcohol consumption, education, marital status, diet quality, current CVD, current cancer, current diabetes, chronic obstructive pulmonary disease and the other physical activity types. The icons at the top represent walking, cycling, domestic work, gardening and sports, from left to right. a For cycling, gardening and sports, the low category refers to not doing that particular activity. Walking is equivalent to 3.0 METs. The median levels of walking across categories are therefore equivalent respectively to 24, 60 and 141 min per day of walking. Average domestic work is equivalent to 3.5 METs.18 The median levels of domestic work across categories are therefore equivalent to 28, 83 and 142 min per day of domestic work. Cycling is equivalent to 4.0 METs. The median levels of cycling across categories are therefore equivalent to 0, 13 and 51 min per day of cycling. Gardening is equivalent to 4.0 METs. The median levels of gardening across categories are therefore equivalent to 0, 9 and 30 min per day of gardening. Average sports is equivalent to 5.5 METs. The median levels of sports across categories are therefore equivalent to 0, 8 and 30 min per day of sports. Figure 2 View largeDownload slide Association of total physical activity in tertiles with overall and cause-specific mortality among participants in the Rotterdam Study, 1997–2014. For every medium and high group, the reference is the low category. The models were adjusted for age, sex, smoking, alcohol consumption, education, current CVD, current cancer, current diabetes and current chronic obstructive pulmonary disease. Total PA is composed of all PA types and thus of different METs. In this regard, the median levels of total PA across categories are equivalent to 1.4, 2.7 and 4.4 h per day of moderate PA equivalent of 4 METs. Figure 2 View largeDownload slide Association of total physical activity in tertiles with overall and cause-specific mortality among participants in the Rotterdam Study, 1997–2014. For every medium and high group, the reference is the low category. The models were adjusted for age, sex, smoking, alcohol consumption, education, current CVD, current cancer, current diabetes and current chronic obstructive pulmonary disease. Total PA is composed of all PA types and thus of different METs. In this regard, the median levels of total PA across categories are equivalent to 1.4, 2.7 and 4.4 h per day of moderate PA equivalent of 4 METs. Cause-specific mortality Higher levels of total PA were associated with lower risk of mortality from CVDs, chronic lung diseases, infections and death from other causes. Each 50 MET·h·week-1 more of total PA was associated with up to 39% lower risk of mortality from CVDs, chronic lung diseases, other causes and infections (Figure 2). Sensitivity analyses Supplementary Tables 2 and 3, available as Supplementary data at IJE online, show the results from all sensitivity analyses of PA types with all-cause mortality, and total PA with cause-specific mortality, respectively. Additional adjustment for BMI in Model 2a and for other biological risk factors in Model 2 b slightly attenuated the associations. In the descriptive analyses stratified by sex, we observed that the mean level of total PA was higher in women than in men, and that domestic work was on average higher in women at 46.2 [standard deviation (SD): 21.3] MET·h·week-1 compared with men at 21.2 (SD: 17.7) MET·h·week-1 (Supplementary Table 4, available as Supplementary data at IJE online). The association between domestic work and all-cause mortality seems to be driven by women. After excluding the first 5 years of follow-up, our results did not materially change. After excluding the first 10 years of follow-up, the associations were attenuated. Noteworthy, we observed a reduction in the strength of the association between total PA and cause-specific mortality with longer exclusion times (Supplementary Figure 2, available as Supplementary data at IJE online). The association in participants without current chronic disease were similar to the main results. Excluding participants in the active labour force did not materially change the effect estimates. In our sensitivity analysis stratified by age, we observed that the associations were stronger in adults aged >65 years. The analyses in cancer-specific mortality did not show any associations (Supplementary Table 5, available as Supplementary data at IJE online). Discussion In this population-based study of older adults aged 55 and over, total PA was associated with a lower risk of mortality due to all causes, CVDs, chronic lung diseases, infections and other causes. In contrast, we did not observe an association of total PA with mortality from cancer, dementia or external causes. All five PA types were associated with a lower risk of all-cause mortality. Our findings underline that engagement in any PA type may be conducive to reducing mortality risk in older adults. Existing literature on cause-specific mortality mostly focused on CVD and cancer mortality.4–6,20,21 Our finding that higher levels of total PA are associated with lower risk of CVD mortality is in agreement with these studies. However, the fact that we did not observe an association with cancer mortality is in contrast to most previous evidence indicating a protective effect from higher PA levels.5,20,22–24 The association between PA and cancer might depend on the cancer site25,26 and it has been suggested that the association between PA and cancer occurs at least 10 years after the activity has been undertaken.6 However, in additional analyses stratifying by the five most frequently occurring cancers in the current study, and in analyses excluding the first 10 years of follow-up, we still observed no association between PA and cancer mortality. The small number of events in the cancer-specific analyses might have led to limited power to detect an association, and the results do suggest a positive association between PA and cancer, which is similar across cancer sites. Future studies with larger sample sizes should further evaluate these associations. There is a paucity of studies regarding mortality related to external causes, dementia, infections and chronic lung diseases. Our finding that PA is associated with reduced mortality related to chronic lung diseases is in agreement with some studies on respiratory disease.12,13,27 The mechanism for the potential beneficial effects of regular PA are unknown, although improved muscle function, exercise capacity and reduced inflammation can be on the causal pathway.12 Although we adjusted for prevalent COPD, our finding might still be related to reversed causality, as participants with undiagnosed lung disease might not be capable of engaging in high levels of PA to begin with. Future studies with careful adjustments should be performed to examine whether higher levels of PA truly decrease the risk for lung disease mortality. In our population, engaging in a median of 13 min/day of cycling (the medium category) was associated with a 28% lower all-cause mortality risk, which is in line with recent evidence that any PA is better than none.28 The mortality risk associated with cycling has been studied before, but conflicting results have been found. Several studies found that cycling to work,4 cycling for commuting20 or cycling for sports21 was associated with lower risk of mortality. In contrast, no association between cycling or walking for transportation and all-cause mortality6 was found among British adults. The way in which cycling was operationalized (commuting to work, any commuting, cycling for sports or all cycling) might contribute to the different findings. Moreover, the age of the participants and the cycling prevalence differed between studies. In studies including younger participants, the lower number of cases might have led to insufficient power to detect an association and in contrast to the UK, cycling is a common method of transportation in The Netherlands, where our study was performed. Domestic work is an important contributor to daily PA, especially in the elderly,10 and was associated with a lower all-cause mortality risk. The associations seemed to be driven by the women in our study, who engaged in domestic work more often than men. Our results are in line with previous studies, observing a lower all-cause mortality risk related to light household activity (<3 METS)5 and activities around the house, including gardening and do-it-yourself activities.6 However, in another study, housework was not associated with all-cause mortality in 50–64-year-old individuals.29 The differences between the studies might be related to the age group studied. This is supported by our analyses in adults <65 years, among whom we found weaker associations between domestic work and mortality. The inverse relation between domestic work and mortality independent of other PA types is consistent with the recommendations emphasizing the importance of moderate-to-vigorous intensity PA performed as part of daily living. We acknowledge that our study has several limitations. It may be hypothesized that people in poor health participate in PA less than others, creating the possibility for reverse causation. After repeating our analyses in participants without prevalent chronic disease, we observed comparable estimates, suggesting that underlying disease did not affect our associations. In contrast, in the analyses excluding the first 5 and 10 years of follow-up, the strength of the association between total PA and cause-specific mortality was attenuated with longer exclusion times. This indicates that we cannot rule out the possibility of reverse causation affecting our results. Additionally, the attenuation of the association observed with increasing exclusion times might be the result of increasing exposure misclassification, as the time span between exposure and outcome classification increases. In the current study, we only measured PA at baseline, which can cause misclassification of PA over time, since PA levels among adults tend to decline with age.30 Due to the prospective design, this misclassification is likely to be non-differential. However, future studies with repeated PA measurements are needed to investigate the effect of exposure misclassification on the association between PA and mortality. Furthermore, we collected no information about occupational PA, so we could not adjust for this in our main analyses. However, excluding participants in the active labour force (n = 828, 11.5%) in our sensitivity analyses revealed comparable estimates. Additionally, our results are based on self-reported PA. Although our questionnaire has shown to be valid and reliable,16 potential recall bias and social desirability cannot be excluded. This limitation could have resulted in bias either towards or away from the null hypothesis. Finally, our questionnaire did not distinguish between walking and cycling for sports or for means of transportation. Since the intensity might differ between sports and transportation,18 future studies are needed to examine the association of the two distinct forms with mortality. Major strengths of the current study are its prospective population-based design, large sample size of adults aged over 55, relatively long follow-up period and inclusion of seven different causes of death. Furthermore, we adjusted for several factors, thereby minimizing the possibility of the observed associations being explained by confounding. In addition, we included a number of different activities while adjusting for the remaining activities, which enabled us to examine their independent associations with all-cause mortality. In summary, in this population of older and elderly adults, we found that PA was associated with a lower risk of mortality from all causes, CVDs, chronic lung diseases, infections and other causes. All the five PA types under investigation contributed to the reduction in the all-cause mortality risk. For public health recommendations, our findings underline that engagement in any type of PA may successfully reduce mortality risk in older adults. Adults incapable of engaging in sports or exercise can engage in any activity that they enjoy and that their health allows them to, including cycling, walking and activities in and around the house. Supplementary Data Supplementary data are available at IJE online. Funding The Rotterdam Study is funded by: Erasmus MC and Erasmus University, Rotterdam, The Netherlands; the Netherlands Organisation for Scientific Research (NWO); the Netherlands Organisation for the Health Research and Development (ZonMw); the Research Institute for Diseases in the Elderly (RIDE); the Ministry of Education, Culture and Science; the Ministry for Health, Welfare and Sports; the European Commission (DG XII); and the Municipality of Rotterdam. O.H.F. works in ErasmusAGE, a centre for ageing research across the life course, funded by Nestlé Nutrition (Nestec Ltd) and Metagenic. Nestlé Nutrition (Nested Ltd) and Metagenics Inc. had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; or preparation, review and approval of the manuscript. L.L. is a Postdoctoral Fellow of the Research Foundation - Flanders (FWO). The work of H.T. was supported by a Netherlands Organisation for Scientific Research grant (017.106.370). Acknowledgements The authors gratefully acknowledge the study participants, the staff from the Rotterdam Study and the participating general practitioners and pharmacists of the Ommoord district. Additionally, we thank Meghan Murphy for carefully editing our manuscript. Author Contributions C.M.K., K.D., J.D.S., L.L., F.J.A.vR., M.A.I., G.B., H.T. and O.H.F. participated actively in each of the following aspects for this article: concep and design or analysis and interpretation of data; drafting the article or revising it critically for important intellectual content; and final approval of the version to be published. Conflict of interest: The authors declare that there is no conflict of interests regarding the publication of the paper. References 1 Physical Activity Guidelines Advisory Committee . Physical Activity Guidelines Advisory Committee Report, 2008 . 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International Journal of EpidemiologyOxford University Press

Published: Apr 16, 2018

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