Light-Intensity Physical Activity in a Large Prospective Cohort of Older US Adults: A 21-Year Follow-Up of Mortality

Background: Studies show that regular moderate to vigorous physical activity is associated with a lower risk of cardiovascular disease, certain cancers, and premature death, but few studies have examined associations of light-intensity physical activity (LPA) and mortality, especially among older adults. Objectives: The aim of this study was to investigate the association of LPA with the risks of death from all causes, cancer, cardiovascular diseases, and respiratory diseases among older adults in the Cancer Prevention Study-II Nutrition Cohort (CPS-II NC). Methods: Analyses included 123,232 participants in CPS-II NC, among whom 46,829 died during follow-up (1993-2014). Cox proportional hazards regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for self-reported leisure time LPA associated with mortality. Results: Engaging in little or no LPA (<3 metabolic equivalent [MET]-h/week) was associated with a 16% higher risk of all-cause mortality (HR 1.16, 95% CI 1.12-1.20) compared to engaging in some LPA (3 to <9 MET-h/week) after adjusting for moderate to vigorous physical activity. However, there was no evidence of a dose-response relationship. A statistically significant interaction with age suggested that more LPA was associated with a lower risk of respiratory disease mortality only among participants aged ≥70 years (21+ vs. 3 to <9 MET-h/week, HR 0.78, 95% CI 0.66-0.91; p_int = 0.003). Conclusions: In this prospective study of older adults, accumulating little/no leisure time LPA was associated with a higher risk of mortality. It is of substantial public health value to demonstrate the potential benefits of engaging in any activity, even if light in intensity, among older adults given the aging US population.