Physical activity, sedentary behavior, and mortality in adults with cardiovascular disease: a NHANES 2007–2018 cohort study

Physical inactivity and prolonged sedentary behavior are common among adults with cardiovascular disease (CVD) and may jointly contribute to increased mortality. However, evidence regarding their combined associations with all-cause and cardiovascular mortality among adults with established CVD remains limited. To examine the individual and joint associations of physical activity and sedentary behavior with all-cause and cardiovascular mortality among US adults with self-reported physician-diagnosed CVD. We conducted a retrospective cohort analysis of adults aged ≥ 20 years with self-reported physician-diagnosed CVD who participated in the 2007–2018 National Health and Nutrition Examination Survey. Moderate-to-vigorous physical activity (MVPA) and sedentary time were assessed using standardized self-report questionnaires. Participants were classified into four joint exposure groups according to physical activity sufficiency and sedentary time. Mortality status was ascertained through linkage to the National Death Index. Survey-weighted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Among 2,434 adults with self-reported CVD included in the fully adjusted complete-case analysis, 710 all-cause deaths and 239 cardiovascular deaths occurred during follow-up. Compared with participants reporting sufficient physical activity and low sedentary time, those reporting insufficient physical activity and high sedentary time had higher all-cause mortality (fully adjusted HR, 1.99; 95% CI, 1.55–2.57) and cardiovascular mortality (HR, 1.70; 95% CI, 1.05–2.74). Insufficient physical activity combined with low sedentary time was associated with higher all-cause mortality (HR, 1.31; 95% CI, 1.04–1.65), whereas sufficient physical activity combined with high sedentary time was not significantly associated with either outcome. Sensitivity analyses consistently supported the all-cause mortality findings. Cardiovascular mortality estimates were less precise given the limited number of events ( n = 239) and were not statistically significant under some alternative sedentary-time definitions and after excluding participants with stroke. Among US adults with self-reported physician-diagnosed CVD, insufficient physical activity combined with high sedentary time was associated with higher all-cause mortality. An association with cardiovascular mortality was also observed in the primary analysis; however, this estimate was based on 239 cardiovascular deaths and was not robust across several sensitivity analyses. The cardiovascular mortality finding should therefore be considered suggestive rather than conclusive.