Even Low Levels of Physical Activity are Associated with Lower All-Cause Mortality: A Cohort Study of 594,000 US Adults

BACKGROUND: Dose-response associations between moderate-to-vigorous physical activity (MVPA) and all-cause mortality are nonlinear, but estimating near-zero activity can be sensitive to exposure construction in national surveillance data. METHODS: We analyzed 594,285 adults from the National Health Interview Survey linked mortality file (1997-2018) with follow-up through 2019. MVPA was quantified as moderate-equivalent minutes per week (moderate + 2×vigorous), explicitly preserving a true-zero category. Survey-weighted Cox proportional hazards models with natural cubic spline were adjusted for demographic, socioeconomic, behavioral, and health-related factors. Hazard ratios (HRs) were estimated relative to 0 minutes/week. Ten-year absolute mortality risk was estimated using inverse probability of censoring weights combined with survey weights. RESULTS: During a median 9.5 years of follow-up (81,689 deaths), 35.8% reported 0 MVPA. Compared with inactivity, adjusted HRs were 0.87 (95% CI: 0.81-0.93) at 5 minutes/week, 0.81 (0.80-0.83) at 150 minutes/week, 0.76 (0.74-0.78) at 300 minutes/week, and 0.74 (0.72-0.76) at 600 minutes/week. Ten-year mortality risk decreased from 19.9% (95% CI: 19.6%-20.2%) at 0 MVPA to 7.2% (6.8%-7.5%) at >600 minutes/week. CONCLUSION: Higher MVPA was associated with lower mortality across a broad range of activity volumes, with the largest gains observed when moving from none to modest activity.