Association of Timing of Physical Activity with Physical Frailty Incidence in Older Adults

Introduction: Maximizing the benefits of physical activity (PA) is important to prevent physical frailty for a measure of this public health issue. This study aimed to investigate the association of timing of PA with the conversion to physical frailty. Methods: This longitudinal observational study enrolled a total of 1,310 community-dwelling Japanese older adults who enrolled in the National Center for Geriatric and Gerontology-Study of Geriatric Syndromes remained as the examined population. A health checkup was conducted to measure baseline characteristics. Subsequently, objectively measured PA was recorded for ≥7 days (≥10 h per day) for 30 days. Daily steps and the morning (6:00–12:00), afternoon (12:00–18:00), and evening (18:00–24:00) steps were calculated. A 2-year follow-up survey was administered to determine the frailty conversion, defined by newly acquired Kihon Checklist scores of 7 or higher. A logistic regression model was constructed with timing of PA and covariates as explanatory variables and frailty conversion as the dependent variable. Results: The number of conversions to frailty was 121 (9.2%). A significant association were observed between evening steps and frailty conversion (log(OR) = −0.44; 95% confidence interval [CI] = −0.87 to 0.03; p = 0.037). No significant associations were observed in the PA of morning (log(OR) = −0.03; 95% CI = −0.51 to 0.55; p = 0.906) and afternoon (log(OR) = −0.36; 95% CI = −0.78 to 0.13; p = 0.117). Conclusions: Evening PA could be advantageous in preventing frailty conversion among community-dwelling older adults. Maximizing the impact of PA may be effective against this public health concern, physical frailty.