Weekly activity-sedentary balance and risk of all-cause mortality and cardiovascular disease: a longitudinal cohort study from China

Physical activity (PA) and sedentary behavior (SB) influence health, but their joint effect is unclear. We examined an integrated PA/SB balance and health outcomes among 10,686 participants in the China Health and Nutrition Survey (1989–2015). All-cause mortality was ascertained through household surveys; incident cardiovascular disease (CVD) was validated by hospital certificates. The Weekly Activity-Sedentary Balance Index (WASBI), a time-varying exposure, was analyzed using time-dependent Cox proportional hazards regression. Over 11.6 years of follow-up, 853 deaths and 560 incident CVD events occurred (CVD subsample n = 6,196). Participants in the third WASBI quartile had the lowest all-cause mortality risk (hazard ratio [HR] = 0.65, 95% CI: 0.53–0.81); CVD risk declined progressively to the fourth quartile (HR = 0.69, 95% CI: 0.47–1.00), attenuated in sensitivity analyses. Each 1-unit WASBI increment was associated with lower all-cause mortality (HR = 0.72, 95% CI: 0.55–0.89) and, more tentatively, lower CVD risk (HR = 0.66, 95% CI: 0.45–0.87). Interaction testing showed this association moderated by BMI for both outcomes. A near-neutral WASBI was associated with lower mortality risk and, more tentatively, lower CVD risk, suggesting risk is lowest not at maximal PA but within a broad PA–SB balance zone.Trial registration Not applicable as no health care intervention on human participants was performed in the present study.