Independent and joint effects of self-reported physical activity and sedentary behaviors on mortality in community-dwelling older persons: a prospective cohort study.

Background: This study aims to assess the joint and independent effects of self-reported physical activity and sedentary behavior on mortality in older persons.

Methods: A prospective community-based cohort study was conducted to examine physical activity (PA) level and sitting time (ST) in relation to mortality among 1,786 older persons aged 65 years and above. PA was assessed by a checklist of 26 self-reported items about PA and hours per week, and the metabolic equivalent hours/week was derived, and ST was measured by a self-reported item asking the average number of hours spent sitting per day. The participants were divided into four combination groups of PA and ST based on WHO guideline and values found in literature: high PA/short ST group, high PA/long ST group, low PA/long ST group, and low PA/short ST group. Data on death ascertainment were obtained through linkage with the national death datasets and expanded cardiovascular disease (CVD) included cardiovascular disease, diabetes, and chronic kidney disease.

Results: After follow-up for a median 11.1 years, 599 mortality cases were recorded, giving a crude all-cause mortality of 32.5/1,000 person-years, CVD mortality of 8.6/1,000 person-years, expanded CVD mortality of 11.9/1,000 person-years, and nonexpanded CVD mortality of 20.8/1,000 person-years. For all-cause, and expanded CVD, the hazards ratios (HRs) for the low PA/long ST group remained significant compared with that for the high PA/short ST group after all covariates were considered [HRs for all-cause mortality: 1.4 [95% confidence interval (CI) 1.1, 1.8]; and expanded CVD mortality: 1.7 (95% CI 1.1, 2.4).

Conclusions: The independent effect of PA and the joint effects of PA and ST are associated with all-cause and expanded CVD death risks. Expanded CVD mortality may be minimized by engaging in PA and reducing sedentary behaviors.