The Association between Cognitive Function and Multimorbidity in Middle-aged and Elderly Populations: A National Longitudinal Study

Background: Multimorbidity is a major public health challenge in an aging society. There is a bidirectional relationship between cognitive function and chronic diseases, but there is still a lack of sufficient evidence regarding how cognitive function prospectively influences the occurrence and development of different multimorbidity patterns. Method: This study is based on the longitudinal data of the China Health and Retirement Longitudinal Study(CHARLS) from 2011 to 2020. A prospective cohort design was adopted, and participants aged 45 and above without multimorbidity at the baseline (n = 4,917) were included. The relationship between baseline cognitive function and the risk of multimorbidity onset was analyzed using the Cox proportional hazards model and restricted cubic spline analysis. The multimorbidity patterns were identified through latent class analysis, and then a multivariate unordered multinomial Logistic regression was used to analyze the differential effects of cognitive function and other factors on different patterns. Results: During the 9-year follow-up period, 56.7% of the participants developed new multimorbidity. After adjusting for confounding factors, higher cognitive function was an independent protective factor for the occurrence of multimorbidity (HR:0.839, 95% CI: (0.753,0.934)), and there was a non-linear relationship ( P < 0.001, P for nonlinear <0.041). When the total cognitive function score was lower than 8.5 points, the risk significantly increased. The study identified four multimorbidity patterns: "multisystem high multimorbidity group", "respiratory system disease dominant group", "mild to moderate joint-digestive system multimorbidity group", and "metabolic syndrome multimorbidity group". The protective effect of cognitive function was particularly evident in significantly reducing the risk of the "mild to moderate joint-digestive system multimorbidity pattern" (OR:0.784, 95% CI :(0.615, 0.999)). In addition, central obesity was a strong risk factor for the "metabolic syndrome multimorbidity group", while a higher level of education was a protective factor for the "respiratory system disease dominant group". Conclusions: Better cognitive function is an important protective factor for preventing the occurrence of multiple multimorbidity in the elderly population, and it has specific protective effects on certain multimorbidity patterns such as the joint-digestive system pattern. Cognitive assessment can serve as an early warning tool for the risk of multimorbidity, and future comprehensive prevention strategies should place emphasis on maintaining cognitive health.