Marcia L. Stefanick, Michael J. LaMonte, David M. Buchner, Kelley R. Evenson, Charles B. Eaton, Andrea Z. LaCroix, Oleg Zaslovsky, Lesly F. Tinker, Chongzhi Di, John Bellettiere, Rebecca Seguin, Cora E. Lewis, I-Min Lee, Eileen Rillamas-Sun
Objectives
To prospectively examine associations between accelerometer-measured physical activity (PA) and mortality in older women, with an emphasis on light-intensity PA.
Design
Prospective cohort study with baseline data collection between March 2012 and April 2014.
Setting
Women's Health Initiative cohort in the United States.
Participants
Community-dwelling women aged 63 to 99 (N = 6,382).
Measurements
Minutes per day of usual PA measured using hip-worn triaxial accelerometers, physical functioning measured using the Short Physical Performance Battery, mortality follow-up for a mean 3.1 years through September 2016 (450 deaths).
Results
When adjusted for accelerometer wear time, age, race-ethnicity, education, smoking, alcohol, self-rated health, and comorbidities, relative risks (95% confidence intervals) for all-cause mortality across PA tertiles were 1.00 (referent), 0.86 (0.69, 1.08), 0.80 (0.62, 1.03) trend P = .07, for low light; 1.00, 0.57 (0.45, 0.71), 0.47 (0.35, 0.61) trend P < .001, for high light; and, 1.00, 0.63 (0.50, 0.79), 0.42 (0.30, 0.57) trend P < .001, for moderate-to-vigorous PA (MVPA). Associations remained significant for high light-intensity PA and MVPA (P < .001) after further adjustment for physical function. Each 30-min/d increment in light-intensity (low and high combined) PA and MVPA was associated, on average, with multivariable relative risk reductions of 12% and 39%, respectively (P < .01). After further simultaneous adjusting for light intensity and MVPA, the inverse associations remained significant (light-intensity PA: RR = 0.93, 95% CI = 0.89–0.97; MVPA: RR = 0.67, 95% CI = 0.58–0.78). These relative risks did not differ between subgroups for age or race and ethnicity (interaction, P ≥ .14, all).
Conclusion
When measured using accelerometers, light-intensity and MVPA are associated with lower mortality in older women. These findings suggest that replacing sedentary time with light-intensity PA is a public health strategy that could benefit an aging society and warrants further investigation.
