The relationship between frailty and multimorbidity in Chinese older adults: the chain mediating effects of sleep quality and anxiety

BACKGROUND: Previous studies have shown an association between frailty and multimorbidity, but the underlying mechanisms are still unclear. Therefore, this study aimed to investigate the potential chain mediating roles of sleep quality and anxiety in the relationship between frailty and multimorbidity. METHODS: This cross-sectional study used data from the first follow-up of the Liyang cohort study on chronic diseases and risk factors monitoring in China (Liyang Study), which comprised 2874 participants aged ≥ 60 years from 17 health centres in Liyang City. Multimorbidity was defined based on 13 self-reported chronic conditions. A modified version of the frailty phenotype was used to assess frailty. Sleep quality and anxiety were assessed using the Pittsburgh Sleep Quality Index and the 7-item Generalized Anxiety Disorder Scale, respectively. Spearman correlation analysis was employed to examine the correlations between frailty, sleep quality, anxiety, and multimorbidity. A chain mediation analysis of sleep quality and anxiety on the relationship between frailty and multimorbidity was conducted using the SPSS PROCESS macro (Model 6). RESULTS: In this study, significant correlations were observed between frailty, sleep quality, anxiety, and multimorbidity (P < 0.01). Frailty had a direct impact on multimorbidity (unstandardised coefficient [B] = 0.196, bootstrap 95% confidence interval [CI] = [0.146, 0.246]). The association was mediated by three important pathways. (1) Sleep quality contributes 26.53% of the total effect (B = 0.052, bootstrap 95% CI = [0.038, 0.068]). (2) Anxiety accounts for 20.92% of the total effect (B = 0.041, bootstrap 95% CI = [0.025, 0.060]). (3) Sleep quality and anxiety represent 5.10% of the total effect (B = 0.010, bootstrap 95% CI = [0.006, 0.015]). The overall mediation effect was 52.55%. CONCLUSIONS: Frailty was positively associated with multimorbidity, and sleep quality and anxiety were important mediators of the association between frailty and multimorbidity. Addressing frailty, enhancing sleep quality, and promoting a positive mood may help reduce multimorbidity and enhance the overall well-being of elderly individuals. This study could potentially contribute to the development of more effective strategies to prevent multimorbidity.