Physical Activity and Risk of Frailty in U.S. Women 60 Yr and Older.

PURPOSE: Several studies have shown a lower risk of developing frailty with long-term higher levels of physical activity. However, most these studies lacked repeated measurement over the follow-up period. Therefore, we examined the association between different types of physical activity and in frailty development using repeated measurements. METHODS: A total of 69,642 nonfrail women 60 yr and older from the Nurses' Health Study were followed from 1992 to 2016. Leisure time physical activity was assessed biennially. Frailty was defined as having 3+ of the following five criteria from the FRAIL scale: fatigue, low strength, reduced aerobic capacity, having ≥5 illnesses, and ≥5% weight loss. Cox models adjusted for potential confounders were used to estimate hazard ratios (HR) and 95% confidence interval (CI) for the association between total, moderate-intensity physical activity, vigorous-intensity physical activity, walking, and incident frailty. RESULTS: During 24 yr of follow-up, we documented 16,479 incident frailty cases. Comparing top to bottom quintiles of MET-hours per week of physical activity, the HR was 0.48 (95% CI = 0.45-0.50) for total physical activity, 0.51 (0.48-0.54) for moderate, and 0.75 (0.71-0.79) for vigorous activity ( Ptrend <0.001 for all activities). For each hour per week increase, HR was 0.56 (0.53-0.58), 0.51 (0.48-0.54), and 0.63 (0.58-0.68) for total, moderate, and vigorous activity, respectively. Walking was the most common activity, and each hour per day increase in walking was associated with an HR of 0.41 (0.38-0.44) for frailty incidence; this was evident even among those older than 70 yr and those with preexisting frailty characteristics. CONCLUSIONS: Both moderate and vigorous physical activities were associated with a lower risk of frailty. In particular, walking, a broadly accessible activity, was also associated with lower risk.