Sitting Time, Physical Activity and Mortality: A Cohort Study In Low-Income Older Americans.

Introduction: Physical inactivity and sedentary behavior are recognized as independent risk factors for many diseases. However, studies investigating their associations with total and cause-specific mortality in low-income and Black populations are limited, particularly among older adults.

Methods: A prospective cohort study was conducted among 8,337 predominantly low-income and Black Americans aged ≥65 years residing in the southern United States. Participants reported their daily sitting time and leisure-time physical activity (LTPA) at baseline (2002-2009), and mortality data were collected through 2019. Analysis was conducted from September 2022 to October 2023.

Results: During a median follow-up of 12.25 years, nearly 50% (n=4,111) were deceased. A prolonged sitting time (>10 hours/day versus <4 hours/day) was associated with elevated all-cause mortality (hazard ratios [HR], 1.15; 95% confidence intervals [CI], 1.04-1.27) after adjusting for LTPA and other potential confounders. LTPA was associated with a reduced risk of all-cause mortality, with an adjusted HR of 0.75 (95% CI 0.64, 0.88) associated with 150-300 minutes per week of moderate-intensity physical activity. Individuals who were physically inactive and had a sitting time of >10 hours/day had the highest mortality risk (HR, 1.48; 95% CI, 1.23-1.78), compared with those who were physically active and had low sitting time. These associations were more pronounced for mortality due to cardiovascular diseases.

Conclusions: High sitting time is an independent risk factor for all-cause and cardiovascular disease mortality, and LTPA could partially attenuate the adverse association of prolonged sitting time with mortality.