A prospective study on the association of sleep duration with grip strength among middle-aged and older Chinese

Background: Longitudinal studies on sleep duration and grip strength decline are limited. This study aimed to evaluate the associations of baseline sleep duration with follow-up grip strength and grip strength changeover time among a large sample of middle-aged and older Chinese. Methods: Data from China Health and Retirement Longitudinal Study, CHARLS (2011-2015), were analyzed. Hand grip strength was measured by dynamometers twice with 4 years interval. Baseline self-reported nighttime sleep duration was collected by questionnaire. Basic demographics, life habits and health status were considered as potential confounders. Multivariate linear regression models with quadratic function and mixed-effects regression models were fitted. Results: Inverted U-shaped associations occurred between baseline sleep duration and follow-up grip strength for both males (beta(linear) = 1.011, p(linear) = 0.002; beta(quadratic) = -0.061, p(quadratic) = 0.014) and females (beta(linear) = 0.605, p(linear) = 0.005, beta(quadratic) = -0.041, p(quadratic) = 0.019). Compared to the sleep duration of 7 h, significant interactions of < 5 hours-by-time (gamma = -0.966 with SEE = 0.442, p = .029) in males as well as 5-7 hours-by-time (gamma= -0.717 with SEE = 0.294, p = .015), 7-9 hours-by-time (gamma = - 0.632 with SEE = 0.311, p = .042) and > 9 hours-by-time (gamma= -1.567 with SEE= 0.560, p = .005) in females were found. Conclusion: For both males and females, compared to the intermediate sleep duration, shorter or longer sleep may predict the weaker follow-up grip strength and the faster rate of hand grip strength decline over time.