Association between frailty and physical-psychological multimorbidity in middle-aged and elderly Chinese adults: Evidence from the China Health and Retirement Longitudinal Study (CHARLS)

Background As the population ages, chronic diseases, frailty, and physical-psychological multimorbidity (PP-MM) increase. However, the association between frailty and PP-MM remains unclear. This study aimed to investigate this relationship in middle-aged and elderly Chinese individuals. Methods This study used four waves of data from the Chinese Longitudinal Study of Health and Aging. Frailty was assessed using the frailty index (FI), and physical illness was defined as having one or more self-reported chronic diseases. Psychological status was examined using the 10-item version of the Centre for Epidemiological Studies Depression Scale. The participants were inquired about any previous diagnoses of affective, emotional, nervous, or psychiatric disorders. PP-MM was defined as the concurrent presence of two kinds of diseases (physical illness and psychological disorders). The relationship between FI and PP-MM was evaluated using COX risk regression models and restricted cubic spline (RCS) curves. Results This study included 10,707 subjects, and after adjusting for potential confounders, the HR was 3.01 (95% confidence interval (CI) = 2.05–4.23) for pre-frail and 6.11 (95% CI = 3.79–9.84) for frail. COX regression analysis indicated a potential association between FI and PP-MM progression. RCS analysis revealed that the risk of PP-MM prevalence increased faster with an FI between 0.10 and 0.25. Conclusion Our study suggests that FI is positively associated with the prevalence of PP-MM and that the pre-frail phase may be a better opportunity to implement interventions for PP-MM prevention, with early monitoring of FI to identify patients at high risk for PP-MM and to provide direction and rationale for preventing PP-MM.