Joint associations of leisure-time physical activity and daily sitting time with mortality among US adults classified as CKM stages 0-3: a prospective cohort study of NHANES 2007-2018.

Abstract

Background: Prior studies have linked physical activity to cardiovascular-kidney-metabolic (CKM) prevalence or mortality and sedentary behavior to CKM severity, and both behaviors are established mortality risk factors in the general population; however, prospective evidence on their joint associations with cause-specific mortality across CKM stages 0-3 remains limited.

Methods: We analyzed 8,556 NHANES 2007-2018 participants aged ≥20 years with CKM stages 0-3, complete prespecified covariates, and a positive fasting-subsample weight. Leisure-time physical activity (LTPA) was categorized as inactive (0 min/week), insufficient (>0 to <150 min/week), or sufficient (≥150 min/week); daily sitting time was categorized as <6, 6 to <8, or ≥8 h/day. The primary outcome was all-cause mortality; cardiovascular disease (CVD) and non-CVD mortality were secondary outcomes. Survey-design-based Cox models incorporated the 12-year fasting weight, strata, and primary sampling units. Multiplicative and additive interactions were assessed.

Results: During a median follow-up of 6.75 years, 670 deaths occurred, including 175 CVD and 495 non-CVD deaths. In fully adjusted models, sufficient versus no LTPA was associated with lower all-cause (hazard ratio [HR], 0.630; 95% confidence interval [CI], 0.483-0.822), CVD (HR, 0.536; 95% CI, 0.297-0.969), and non-CVD mortality (HR, 0.662; 95% CI, 0.478-0.916). Sitting ≥8 versus <6 h/day was associated with higher all-cause (HR, 1.506; 95% CI, 1.253-1.810), CVD (HR, 1.845; 95% CI, 1.246-2.732), and non-CVD mortality (HR, 1.406; 95% CI, 1.109-1.782). Compared with sufficient LTPA and sitting <6 h/day, <150 min/week of LTPA combined with sitting ≥8 h/day was associated with all-cause (HR, 1.972; 95% CI, 1.429-2.721), CVD (HR, 2.493; 95% CI, 1.232-5.045), and non-CVD mortality (HR, 1.806; 95% CI, 1.202-2.712). Multiplicative interaction was not detected for all-cause (P = 0.951) or non-CVD mortality (P = 0.274); the CVD interaction signal (P = 0.016) was exploratory because it depended on a joint category with few events.

Conclusion: Higher LTPA and shorter sitting time were independently associated with lower mortality among US adults with CKM stages 0-3. Joint categories identified a higher-risk behavioral pattern, but did not establish that LTPA offsets the risk of prolonged sitting.