Physical Activity and Sitting over 9 years of the Women’s Health Initiative Strong & Healthy ( WHISH ) Randomized Physical Activity Intervention Trial in Older Women

BACKGROUND: The Women's Health Initiative (WHI) Strong & Healthy (WHISH) randomized trial implemented a 9-year remotely-delivered "light touch" multicomponent physical activity intervention (PA-I) aimed at increasing physical activity (PA) and reducing sitting time in a large U.S. cohort of older women. METHODS: Using a randomized consent design, 49,331 women, aged 66-99 years, were assigned to Intervention (N = 24,657), 95.9% (N = 23,653) of whom provided passive consent to receive the WHISH PA-I, or "usual activity" Comparison (N = 24,674). Differences between intention-to-treat arms in self-reported walking, sitting and other PA, averaged over the course of the trial, were derived from a linear regression model with log-transformed outcomes as a function of arm, adjusted for participant selection strata. RESULTS: Pre-randomization mean age (79.7 years), total recreational PA (11.6 MET-hours/week), RAND-36 physical function score, and other characteristics did not differ between trial arms. Over a median 8.7 years, Intervention participants reported higher average walking (3.2%), aerobic (3.4%) and total (3.7%) exercise, as MET-hours/week, and strength training sessions per week (4.4%), and fewer hours/week of sitting (1.5%) than Comparison (p < 0.001 for all). Intervention versus Comparison differences were greater for aerobic exercise (6.92%) and sitting (-2.48%) in the youngest age group (66-76) compared with other age groups (p for interaction <0.001 and 0.02, respectively). CONCLUSION: A 9-year "light touch" remotely-delivered PA intervention modestly attenuated age-related PA decreases and sitting time increases in older women. Building on the pragmatic WHISH PA intervention to augment behavioral changes, especially in adults aged over 80 years, is an important direction for population health.