Association between frailty and physical-psychological multimorbidity in middle-aged and elderly Chinese adults: a longitudinal study in Chinese middle-aged and older adults.

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. The main measures included frailty by the frailty index(FI) constructed using 40 indicators. 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 and P < 0.05 was considered statistically significant.

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.