Longitudinal analysis of sleep duration trajectories and sarcopenia risk in middle-aged and older Chinese adults: evidence from China health and retirement longitudinal study.

OBJECTIVES: Sarcopenia has emerged as a significant public health issue that threatens the health of older adults. The association between sleep duration and sarcopenia is receiving increasing attention. Based on data from the China Health and Retirement Longitudinal Study (CHARLS), this study investigates the dynamic characteristics of sleep duration trajectories and their relationship with the onset of sarcopenia. DESIGN: A retrospective cohort study. SETTING: The study used data from the CHARLS across various regions of China. PARTICIPANTS: Data were drawn from the 2011, 2013 and 2015 waves of CHARLS, including 2521 participants aged 45 years or older at baseline who had complete 3-year records of sarcopenia diagnosis. Sarcopenia was defined according to the 2019 criteria established by the Asian Working Group for Sarcopenia and was assessed across three dimensions: grip strength, estimated appendicular skeletal muscle mass and physical function. OUTCOME MEASURES: Participants were categorised by changes in sleep duration, and linear mixed-effects models were used to identify three trajectories of sleep duration change (decrease-increase, decrease-no recovery and continuous increase). Multivariate logistic regression was conducted to examine the association between these trajectories and the risk of sarcopenia, adjusting for confounders, such as education level, body mass index (BMI) and lifestyle factors. RESULTS: The median age of the cohort was 57.00 years, 61.40% of participants were female and the median BMI was 23.44. During the 5-year follow-up, the prevalence of sarcopenia was 14.09%. Compared with the non-sarcopenia group, individuals with sarcopenia had a higher median age (60.00 vs 56.00 years, p<0.001), lower BMI (23.06 vs 23.44, p=0.020), a higher proportion of unmarried/divorced individuals (16.34% vs 11.5%, p=0.010) and lower education levels (p<0.001). After adjusting for gender, age, BMI, residential area, education level, marital status, health insurance status, smoking and alcohol consumption, both increased and decreased sleep durations were associated with higher odds of sarcopenia relative to unchanged sleep duration, though the associations were not statistically significant (increased sleep duration: OR=1.081, 95% CI 0.807 to 1.449, p=0.601 and decreased sleep duration: OR=1.225, 95% CI 0.928 to 1.618, p=0.153). These results remained non-significant after further multivariate adjustment. Analysis of the three sleep duration trajectories identified via the linear mixed-effects model showed that, after multivariate adjustment and in comparison with trajectory 1 (sleep duration decreased and then increased significantly, exceeding baseline levels), both trajectory 2 (sleep duration decreased and then slightly increased but remained below baseline) and trajectory 3 (a consistent increase in sleep duration) were associated with a potential reduction in sarcopenia risk. However, these associations were not statistically significant (trajectory 2: OR=0.833, 95% CI 0.620 to 1.120, p=0.226 and trajectory 3: OR=0.844, 95% CI 0.647 to 1.101, p=0.210). CONCLUSIONS: This study developed a novel sleep trajectory model using longitudinal data, revealing the non-linear, multidimensional nature of the relationship between sleep duration and sarcopenia risk. Although no independent association was identified between 5-year sleep duration trajectories and sarcopenia in Chinese middle-aged and older adults, the study provides a valuable methodological framework for exploring multifactorial interactions in the ageing process and establishes a foundation for future research.