Does the association between physical activity during work and leisure and blood pressure differ across sex? A cross-sectional compositional data analysis in a Danish population-based cohort

BACKGROUND: A proposed risk factor for cardiovascular disease is high occupational physical activity (OPA), which seems to increase blood pressure (BP), in contrast to leisure time physical activity. Increased BP may lead to hypertension that increase the risk of cardiovascular disease and premature death. Exposures to OPA differ across sex and also within occupational group. Thus, we aimed to investigate associations between OPA and LTPA and BP among men and women using compositional data analysis. METHODS: This population-based cross-sectional study, used data from the Copenhagen Aging and Midlife Biobank. OPA and LTPA were self-reported time spent in light physical activity (LPA) during work = standing or walking work; moderate-to-vigorous physical activity (MVPA) during work = heavy manual work; LPA during leisure = light physical activity during leisure; MVPA during leisure = biking or walking as commute to work + daily amount of MVPA during leisure, and sleep. Systolic and diastolic BP (SBP, DBP; mmHg) was measured during sitting rest. We used linear regression models to investigate the association between OPA and LTPA, expressed as isometric log-ratios, and BP. The models were used to predict the BP for reallocated physical activity (PA) compositions (i.e., theoretically 'moving' time from sitting to PA within each domain). Specifically, we predicted the BP for each reallocated PA compositions and calculated the difference in BP between the reallocated compositions and the mean composition. RESULTS: In total, 1,334 women and 2,983 men (mean age 55.1 and 52.5 years, respectively) were included in the analyses. About 50% of the women, and 66% of the men, had hypertension. The linear regressions based on the compositional data analysis, showed no association between OPA and LTPA and SBP among women or men. Among men, less time spent sitting and more time spent in LTPA, compared to the mean composition, was associated with a lower DBP (e.g., 60 min less sitting and 60 min more LTPA: -0.25, 95% CI: -0.05, -0.45 mmHg). CONCLUSION: No association between OPA and LTPA and BP was observed across sexes, except between LTPA and DBP among men. This could be due to information bias and lack of precision in self-reported time use data of PA. TRIAL REGISTRATION: None.