Body weight status and onset of cognitive impairment among US middle-aged and older adults

Objective: To examine the relationship between body weight status and onset of cognitive impairment among U.S. middle-aged and older adults. Methods: Study sample came from 1996 to 2010 waves of the Health and Retirement Study, consisting of 6739 community-dwelling adults born between 1931 and 1941 who were free from cognitive impairment in 1996. Body mass index (BMI) was calculated from self-reported height/weight. Cognitive impairment was defined by a composite score of 11 or lower on the immediate and delayed word recall, serial 7's, and backwards counting tests. Kaplan-Meier estimator and Cox proportional hazards model were performed to examine the association between base-year body weight status and future onset of cognitive impairment. Results: Compared with their normal weight counterparts, the unadjusted hazard ratio (HR) for cognitive impairment incidence was 2.03 (95 confidence interval: 1.38-3.00), 1.15 (1.02-1.29), 1.28 (1.14-1.43), and 1.59 (1.33-1.92) among underweight (BMI 18.5), overweight (25 = BMI 30), class I obese (30 = BMI 35), and class II obese or above (BMI = 35) participants, respectively. The unadjusted relationship between obesity and cognitive impairment onset appeared stronger among females than among males. After adjusting for base-year individual sociodemographics, functional limitations and chronic conditions, the estimated associations between body weight status and cognitive impairment were attenuated but remained statistically significant for underweight participants. Conclusion: Underweight is a robust risk factor for onset of cognitive impairment in later life. Weight management programs targeting middle-aged and older adults should focus on achieving and maintaining optimal body weight. (C) 2015 Elsevier Ireland Ltd. All rights reserved.