Abstract
BACKGROUND: Frailty, defined as diminished physiological and functional reserve, is linked to negative health outcomes such as falls, fractures, and disability. Physical activity dose plays a significant role in preventing and reducing physical frailty, but the influence of different PA variables on deficit accumulation (ie, frailty index [FI]) is not fully understood. Thus, we examined the relationship between physical activity variables and FI among older adults. METHODS: We utilized Round 11 (2021) data from the National Health and Aging Trends Study, a longitudinal study of Medicare beneficiaries aged 65 and older in the United States. Our participants included 726 community-dwelling older adults who had at least 3 valid days of accelerometer data and all data needed to calculate FI. Demographic variables, health conditions, and physical function were assessed through standardized interviews and objective assessments. We completed regression and Poisson models to estimate FI value and prevalence ratios for frailty. RESULTS: Participants spent 339 daily minutes performing physical activity. The activity was accumulated over 88 bouts averaging 3.8 minutes. Those with frailty have lower levels of activity, higher levels of non-activity and sleep, higher activity fragmentation, fewer bouts, shorter bouts, and lower intensity over 10 consecutive minutes (ps < .001). After adjusting for all activity metrics, activity fragmentation (B = 1.32) and intensity of the most active 10-minute bout (B= -0.46) remained significantly associated with FI (P ≤ .04). CONCLUSIONS: Low-intensity and fragmented physical activity is linked to frailty. Further research should explore the role of sustained activity and fragmentation in monitoring and guiding interventions for frailty.