Body mass index and cognitive decline in a biracial community population.

OBJECTIVE: To examine whether a higher body mass index (BMI) in older adults is associated with greater cognitive decline.

METHODS: A longitudinal study was conducted from 1993 to 2003 with an average follow-up of 6.4 years of a biracial community population on the south side of Chicago. Participants were 3,885 community-dwelling adults aged 65 and older who participated in at least two assessments. A composite measure of global cognitive function was used which was derived from the average of standardized scores from four cognitive tests.

RESULTS: There was a significant curvilinear association between BMI and cognitive function scores at baseline for both black (= -0.0014, p = 0.001) and non-black subjects (= -0.0011, p = 0.002). In a mixed model adjusted for age, sex, race, and education, higher BMI was associated with less cognitive decline in both black (= 0.0013, p = 0.009) and non-black subjects (= 0.0021, p = 0.006). Adjusting for comorbid illnesses did not change these findings substantially. However, the associations were much smaller and no longer significant among participants with no cognitive decline at baseline as measured by a Mini-Mental State Examination score of greater than 24.

CONCLUSIONS: The findings suggest that greater body mass index in old age is not predictive of cognitive decline in a cognitively unimpaired community population.