Longitudinal association between sarcopenia and comorbidity of mild cognitive impairment and depression among older adults in China: the moderating effect of non-obesity

BACKGROUND: Sarcopenia, mild cognitive impairment (MCI), and depression could cause great distress in the lives of older adults and frequently co-occur, yet their interrelationships remain elusive. This study seeks to assess the link between sarcopenia and the comorbid MCI and depression in older Chinese, and their longitudinal impact. METHODS: We used data from the 2015 (wave 3) and 2018 (wave 4) surveys of the China Health and Retirement Longitudinal Study (CHARLS). Cross-sectional analysis of the 2015 data estimated the baseline prevalence of sarcopenia and its comorbidity with mild cognitive impairment (MCI) and depression. Longitudinal analysis of the 2015-2018 data employed multivariate logistic regression models, adjusted for demographic and health covariates, to examine the prospective association between sarcopenia and incident comorbidities; stratified analyses were additionally conducted among obese individuals. To illustrate the impact of sarcopenia on comorbidity onset, Cox proportional-hazards models were fitted to the 2011-2018 (waves 1-4) longitudinal data to estimate the association between sarcopenia and incident comorbidities. RESULTS: During the follow-up period from 2015 to 2018, among 2773 individuals, 190 developed comorbidities of mild cognitive impairment 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% points 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: 2.578-22.289, 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. However, in the non-obese subgroup, neither possible sarcopenia group (OR = 1.875, 95% CI: 0.858-4.097, P > 0.05) nor sarcopenia group (OR = 1.222, 95% CI: 0.590-2.529, P > 0.05) showed a statistically significant association with the development of comorbidity. CONCLUSION: These findings suggest that sarcopenia increases the risk of comorbid MCI and depression in older adults; however, this association was only observed in obese individuals, with non-obesity status significantly attenuating the risk. These findings suggest that sarcopenia may represent a potential target for preventive strategies, particularly among obese older adults.