Associations between dimensions of physical activity (intensity, frequency, duration, and volume) and frailty among middle-aged and older Chinese adults.

Objectives: Physical activity (PA) plays an essential role in preventing and delaying frailty. Although several studies have examined the association between PA and frailty in middle-aged and older adults, no research has considered all four PA dimensions including intensity, duration, frequency, and volume. This study examined the association between PA dimensions and the prevalence of frailty, and established PA cut-points for detecting the presence of frailty. Methods: A total of 9389 individuals aged 40 or older from the China Health and Retirement Longitudinal Study were involved in this cross-sectional study. Frailty was assessed using the frailty index, which was calculated by the health deficit items. A self-reported questionnaire was used to collect information about PA intensity, duration, frequency, and volume. We employed logistic regression analysis to determine the associations between dimensions of PA and frailty, and receiver operating characteristic (ROC) curve analysis to examine the optimal PA cut-point for predicting frailty according to gender and age. Results: The prevalence of frailty was 10.6 % in middle-aged and older adults. Spending at least 1-2 days, 10-29 min per day, and 10-149 min each week in vigorous-intensity PA, moderate-intensity PA or light-intensity PA were all related to a lower likelihood of frailty, with adjusted ORs (95 % CI) ranging from 0.21 (0.12, 0.37) to 0.56 (0.41, 0.75). A sensitivity analysis demonstrated that the association between the dimensions of PA and frailty remained unchanged after employing an alternative frailty criterion. ROC curves analysis indicated that the optimal PA cut-points to predict frailty were 733, 693, 693, and 471 MET-minutes per week for men, women, middle-aged adults, and older adults, respectively. Conclusions: Regardless of PA intensity, even a short duration and low frequency of PA is linked to a lower likelihood of frailty. For middle-aged and older adults, the lower PA value may serve as an early sign indicating a greater prevalence of frailty. The findings provide insight into therapies aimed at preventing and treating frailty in middle-aged and older adults.