Association between cumulative body mass index exposure and cognitive function among elderly people aged 60 years and older in China

Abstract

Objective: To analyze the relationship between cumulative body mass index (BMI) and cognitive score or cognitive impairment at different age groups among elderly adults aged≥60 years old. Methods: Participants were recruited from the Prediction for Atherosclerotic Cardiovascular Disease Risk in China (China-PAR). A total of 27 227 participants aged≥60 years old, who completed at least 2 physical examinations between 1992-1994 and 2018-2021, and completed cognitive function tests from 2018 to 2021, were included in the final analysis. Cognitive score was assessed using the Minimum Mental State Examination (MMSE). Cognitive impairment was defined based on education level: illiterate individuals with MMSE≤17, primary school graduates with MMSE≤20, and secondary school graduates with MMSE≤24. Multivariate linear regression or multivariate logistic regression models were used to analyze the association between 10-year weighted cumulative BMI and cognitive score or cognitive impairment in the general population, as well as in specific age groups (including 60-64 years, 65-69 years, 70-74 years, and≥75 years). Restricted cubic spline was adopted to explore the dose-response relationship. Results: The age of enrolled participants was (72.3±5.8) years, and 10 639 (39.1%) were males. The mean MMSE score was (24.9±6.8), and 4 171 (15.4%) participants had cognitive impairment. In the general population, the MMSE score increased and the risk of cognitive impairment decreased with the increase in cumulative BMI when cumulative BMI was280 kg/m2 (β=0.095, 95%CI: 0.060-0.130; OR=0.962, 95%CI: 0.946-0.978). When cumulative BMI≥280 kg/m2, the associations between cumulative BMI level and MMSE score and cognitive impairment risk were not statistically significant (β=-0.105, 95%CI:-0.212-0.001; OR=1.047, 95%CI: 0.992-1.102). Subgroup analysis according to age groups revealed a potential"U-shaped"correlation between cumulative BMI and MMSE score or cognitive impairment risk in participants aged75 years old. For cumulative BMI levels280 kg/m2, the OR and 95%CI for cognitive impairment were 0.983 (0.904-1.069), 0.953 (0.919-0.987), and 0.951 (0.922-0.982) for each 10 kg/m2 increment in cumulative BMI in the 60-64, 65-69, and 70-74 years old groups, respectively. For cumulative BMI≥280 kg/m2, the OR and 95%CI were 1.548 (1.134-2.186), 1.037 (0.938-1.139), and 1.109 (1.014-1.208) in the 60-64, 65-69, and 70-74 age groups. Among those aged≥75 years old, the cumulative BMI level was statistically associated with the increased MMSE score and decreased cognitive impairment (β=0.132, 95%CI: 0.074-0.190; OR=0.961, 95%CI: 0.944-0.979). Conclusions: Overall, when cumulative BMI is280 kg/m2, an increase in cumulative BMI is associated with a reduced risk of cognitive impairment in the general population. However, the association varies among individuals aged75 years old and those≥75 years old when cumulative BMI is≥280 kg/m2. The findings highlight the necessity of personalized weight management strategies for elderly individuals across different age groups.