Sedentary behavior as a risk factor for physical frailty independent of moderate activity: Results from the osteoarthritis initiative

Objectives. This prospective longitudinal study investigated the association between baseline objectively measured sedentary time and 2-year onset of physical frailty. Methods. We studied 1333 Osteoarthritis Initiative participants 55 to 83 years of agewho were at risk for physical frailty, as assessed via lowgait speed (< 0.6mper second) or inability to perform a single chair stand. Baseline sedentary time was assessed through accelerometer monitoring. Hazard ratios (HRs) for physical frailty onset were estimated with discrete survival methods that controlled for moderate physical activity, sociodemographic characteristics, baseline gait and chair stand functioning, and health factors. Results. The incidence of physical frailty in this high-risk group was 20.7 per 1000 person-years. Greater baseline sedentary time (adjusted HR= 1.36 per sedentary hour; 95% confidence interval [CI] = 1.02, 1.79) was significantly related to incident physical frailty after control for time spent in moderate-intensity activities and other covariates. Conclusions. Our prospective data demonstrated a strong relationship between daily sedentary time and development of physical frailty distinct from insufficientmoderate activity. Interventions that promote reductions in sedentary behaviors in addition to increases in physical activity may help decrease physical frailty onset.