The Impact of a Long-Term Structured Physical Activity Intervention on Frailty Trajectory and Mobility Disability

by Jack Quach, Dr. Olga Theou, Dr. Ulises Pérez-Zepeda, Dr. Judith Godin, Dr. Scott Kehler

Abstract: We examined the effect of a two-year physical activity (PA) intervention on frailty trajectory and on major mobility disability (MMD) across baseline frailty levels. We analyzed data from 1,635 community-dwelling participants from the Lifestyle Interventions and Independence Study who were 70-89 years old (mean baseline age [SD]: 78.9 [5.2 years], 67.0% female). Participants were randomized to either moderate intensity PA or health education (HE) groups. Frailty was measured with a 44-item frailty index (FI) created from the study questionnaires, using standardized procedures; scores range from 0 (healthy) to 1 (severely frail). MMD was determined by the inability to complete a 400m walk test within 15 minutes without sitting or person- or walking aid assistance. Linear mixed-effects models estimated frailty trajectory. Cox regression models were used, centering FI at 0.05 intervals, to determine if the effect of PA on MMD differed by baseline FI. The mean (SD) FI at baseline was 0.18 (0.10) for both groups. MMD rates were 28.3% (246/818) and 34.5% (290/817) for the PA and HE groups, respectively. Linear mixed-effects models showed that the FI trajectory was not different across interventions (p = 0.303). When FI was centered at 0.15 or higher, PA was associated with lower MMD risk when compared to HE (odds ratio range [95% CI]: 0.65-0.81 [0.43-0.98]). At lower FI (0-0.1), PA was not different than HE in regard to MMD risk. Frailty trajectory was similar across both PA and HE groups. PA intervention reduced the risk of MMD in those who were frailer.