Revisiting the association of sedentary behavior and physical activity with all-cause mortality using a compositional approach: the Women's Health Study

Background: while physical activity has consistently been associated with decreased mortality rates, it remains unknown if there is a single 'ideal' combination of time in physical activities of different intensities and sedentary behavior (SB) associated with the lowest rate. This study examined the associations of combinations of time in moderate-to-vigorous intensity (MVPA), higher-light intensity (HLPA), lower-light intensity activities (LLPA), and SB with mortality rates in older women. Methods: this prospective cohort study included 16,676 older women from throughout the United States enrolled in the Women’s Health Study. Women wore accelerometers on their hip from 2011 to 2015 and were followed through 2017 (mean (SD) of 4.3 (1.1) years). Deaths were confirmed with medical records, death certificates, or the National Death Index. Compositional Cox regression models were used. Results: the mean (SD) age was 72 (5.7) years at accelerometer wear; 503 women died. Compared to the least active women (mean, 3 min/day MVPA, 27 min/day HLPA, 162 min/day LLPA, and 701 min/day SB): compositional models showed an inverse L-shaped dose-response association of MVPA replacing other behaviors with mortality rates mortality rates (P =.02); SB relative to LLPA, HLPA, and MVPA was directly associated with mortality rates in a curvilinear dose-response manner (P <.001); replacing 10 min of SB for MVPA (HR (95% CI) =.86 (.73–.98)) or for HLPA (HR (95% CI.94 (.88–1.00)) associated with 14 and 6% lower mortality rates, respectively; a 47% risk reduction (HR [95% CI] =.53 [.42–.64]) was observed among women meeting physical activity guidelines (mean, 36 min/day MVPA, 79 min/day HLPA, 227 min/day LLPA and 549 min/day SB); and similar mortality rate reductions of 43% (HR (95% CI) =.57 (.41–.73)) were observed with increases in HLPA and LLPA without increasing MVPA, e.g., reallocating SB to 90 min/day of HLPA plus 120 min/day of LLPA. Conclusions: there was no 'ideal' combination of physical activities of different intensities and SB associated with the lowest mortality rates. Of particular relevance to older women, replacing SB with light intensity activity was associated with lower mortality rates, and 'mixing and matching' times in different intensities yielded equivalent mortality risk reductions.