Cognitive function in normal-weight, overweight, and obese older adults: An analysis of the advanced cognitive training for independent and vital elderly cohort

OBJECTIVES: To assess how elevated body mass index (BMI) affects cognitive function in elderly people. DESIGN: Cross-sectional study. SETTING: Data for this cross-sectional study were taken from a multicenter randomized controlled trial, the Advanced Cognitive Training for Independent and Vital Elderly trial. PARTICIPANTS: The analytic sample included 2,684 normal-weight, overweight, or obese subjects aged 65 to 94. MEASUREMENTS: Evaluation of cognitive abilities was performed in several domains: global cognition, memory, reasoning, and speed of processing. Cross-sectional association between body weight status and cognitive functions was analyzed using multiple linear regression. RESULTS: Overweight subjects had better performance on a reasoning task (beta=0.23, standard error (SE)=0.11, P=.04) and the Useful Field of View (UFOV) measure (beta=-39.46, SE=12.95, P=.002), a test of visuospatial speed of processing, after controlling for age, sex, race, years of education, intervention group, study site, and cardiovascular risk factors. Subjects with class I (BMI 30.0-34.9 kg/m(2)) and class II (BMI > 35.0 kg/m(2)) obesity had better UFOV measure scores (beta=-38.98, SE=14.77, P=.008; beta=-35.75, SE=17.65, and P=.04, respectively) in the multivariate model than normal-weight subjects. The relationships between BMI and individual cognitive domains were nonlinear. CONCLUSION: Overweight participants had better cognitive performance in terms of reasoning and visuospatial speed of processing than normal-weight participants. Obesity was associated with better performance in visuospatial speed of processing than normal weight. The relationship between BMI and cognitive function should be studied prospectively.