A 6-year cohort study of the associations of body mass index, waist circumference, and waist-hip ratio with cognitive impairment in Chinese elderly.

OBJECTIVES

Current findings from cohort studies examining the association between obesity and cognitive impairment are inconsistent, particularly with regard to central obesity. This study aimed to investigate the prospective associations of Body Mass Index (BMI), Waist Circumference (WC), and Waist-Hip Ratio (WHR) with the risk of cognitive impairment among Chinese elderly.

METHODS

We used data from the Zhejiang Healthy Aging Cohort Study (ZHACS), which included 8,443 participants. BMI, WC, and WHR were assessed using a baseline questionnaire that was initiated in 2014. Cognitive function was evaluated using the Mini-Mental State Examination (MMSE) at baseline and three waves of follow-up (2015, 2016, and 2019-2021), with cognitive impairment based on thresholds tailored to participants' educational backgrounds. Log-binomial regression models adjusted for numerous covariates were used to examine the associations and calculate relative risks (RRs).

RESULTS

After 6 years of follow-up, 3,006 participants (35.60%) showed cognitive impairment at least once, according to the MMSE. BMI-defined underweight was positively associated with cognitive impairment (RR = 1.15; 95%CI: 1.05-1.27). Conversely, inverse associations were identified for central obesity defined by WC and WHR, with estimated effect sizes of 14% (RR = 0.86; 95%CI: 0.81-0.91) and 9% (RR = 0.91; 95%CI: 0.86-0.97), respectively. Participants with both BMI-defined overweight/obesity and WC/WHR-defined central obesity had a significant inverse association with cognitive impairment, whereas those with both BMI-defined underweight and WC/WHR-defined central obesity did not. Stratified analyses indicated that the association of BMI-defined underweight and WHR-defined central obesity with cognitive impairment was more evident among women participants and individuals aged ≥70 years.

CONCLUSION

Among Chinese older adults, BMI-defined underweight was significantly positively associated with cognitive impairment, whereas WC-defined and WHR-defined central obesity was inversely associated with cognitive impairment, particularly among older adults (≥70 years) and women.