Objectively Measured Physical Activity and Mortality Risk Among American Adults.

INTRODUCTION: One major limitation of prior studies examining the influence of physical activity on mortality is use of self-reported measures. This study examined the association between objectively measured light physical activity (LPA) and moderate to vigorous physical activity (MVPA) and all-cause mortality.

METHODS: This study included 5,562 adults from the 2003-2006 National Health and Nutrition Examination Survey. LPA and MVPA were measured over 4-7 days using Actigraph AM-7164 accelerometers. For both activity intensities, the first quintile defined low participation and the remaining quintiles defined modest to high participation. Information on age, sex, race, SES, diet, smoking, and alcohol were collected and controlled for. Survival status through December 31, 2011, was determined. Average follow-up was 6.7 years. Data were analyzed in 2015.

RESULTS: In women, the all-cause mortality hazard ratio (HR) was 0.58 (95% CI=0.38, 0.88) for modest to high LPA and 0.34 (95% CI=0.20, 0.57) for modest to high MVPA. Corresponding HRs in men were 1.02 (95% CI=0.64, 1.61) and 0.39 (95% CI=0.27, 0.56). Compared with women with a low LPA/low MVPA combination, mortality risk was reduced in the modest to high LPA/low MVPA (HR=0.42, 95% CI=0.26, 0.70), low LPA/modest to high MVPA (HR=0.16, 95% CI=0.07, 0.34), and modest to high LPA/modest to high MVPA (HR=0.17, 95% CI=0.09, 0.36) combinations. In men, mortality risk was not reduced with modest to high LPA/low MVPA.

CONCLUSIONS: MVPA was associated with a substantially lower mortality risk. LPA was associated with lower mortality risk, but only within women with low MVPA.