Association between sarcopenia and comorbidity of mild cognitive impairment and depression among elderly individuals in China: the moderating effect of non-obesity

Background Sarcopenia, mild cognitive impairment (MCI), and depression could cause great distress in the lives of the elderly and frequently co-occur, yet their interrelationships remain elusive. This study seeks to assess the link between sarcopenia and the comorbidity of MCI and depression in older Chinese, and their longitudinal impact. Methods This prospective cohort study analyzed cognitive data from the China Health and Retirement Longitudinal Study (CHARLS), including the baseline survey conducted in 2015 and the follow-up survey conducted in 2018. Researchers utilized χ ² tests and logistic regression to assess the association between sarcopenia and comorbidities. In longitudinal analyses, χ ² tests compared comorbidity prevalence across sarcopenia groups, while logistic regression examined the link between sarcopenia occurrence and comorbidities, including the effects in obese individuals. Results During the follow-up period from 2015 to 2018, among 2773 individuals, 190 developed comorbidities of cognitive decline and depression. After adjusting for covariates, compared to non-sarcopenic individuals, those with possible sarcopenia (OR = 2.952, 95% CI: 2.104–4.141, P<0.01) and sarcopenia (OR = 3.105, 95% CI: 2.064–4.670, P<0.01) were associated with a higher incidence of comorbidity (p < 0.001). Furthermore, we observed that the incidence of comorbidity was 15.38% lower in non-obese individuals with sarcopenia compared to those who were obese and had sarcopenia. Compared to the normal group, individuals with obesity who had possible sarcopenia exhibited a higher risk of developing comorbidities. (OR = 2.411, 95% CI: 1.472–3.946, P<0.001), and the sarcopenia group had an even higher risk (OR = 7.580, 95% CI: 2578-22.289, P<0.001) in the fully adjusted model accounting for age, gender, residential area, education level, marital status, former/current smoking, former/current alcohol use, other comorbidities. Conclusion From the study, we find that sarcopenia correlates with MCI and depressive comorbidities in elderly Chinese, an association that becomes non-significant with normal BMI and waist circumference.