Body Mass Index and Decline in Cognitive Function in Older Black and White Persons
Background While body mass index (BMI) is higher in black compared to white persons, little is known about BMI and change in cognition in cohorts with a large proportion of blacks. We examine relations of BMI with decline in global cognition and five cognitive domains, in older blacks and whites, and determine whether relations differ by race. Methods Participants were 2,134 persons without baseline dementia (33% black; 75% women; mean age =77.9 [range 53 100] and education 14.7 years, Mini Mental State Examination 28.0) enrolled in one of two longitudinal, community based cohort studies of aging (Minority Aging Research Study; Rush Memory and Aging Project) Summary scores of global cognition and five domains were based on 19 neuropsychological tests administered annually. Mixed effects models, controlling for age, sex, education, and race, were used to examine the relation of baseline BMI to change in cognition. Results Baseline BMI 28.4 units (30.3 in blacks [95% confidence interval (CI) 27.2 27.7] 27.4 in whites [95% CI: 29.8 30.7] During a mean annual follow up of 6 years (SD 4) lower baseline BMI was related to faster decline in global cognition (p .002) and semantic memory (p .001) and episodic memory (p .004) but not working memory, perceptual speed, or visuospatial ability (all p .08) The relationship of BMI with change in cognition was not modified by race (all p .09) Conclusions Late life lower BMI relates to faster rates of decline in cognition, specifically semantic memory and episodic memory, in both blacks and whites. The effect of BMI on cognition appears to be similar in both racial groups.
The journals of gerontology. Series A, Biological sciences and medical sciences