Relation between body mass index and cognitive function in healthy middle-aged men and women.

OBJECTIVE: To assess whether body mass index (BMI) is associated with cognitive function and cognitive decline in healthy men and women.

METHODS: In this prospective cohort study, we analyzed data from 2,223 healthy workers aged 32 to 62 years at baseline. Medical, psychosocial, and environmental data were collected in 1996 and in 2001. We tested cognitive functions at baseline and at follow-up with word-list learning (four recalls), a Digit-Symbol Substitution Test, and a selective attention test.

RESULTS: Cross-sectionally, a higher BMI was associated with lower cognitive scores after adjustment for age, sex, educational level, blood pressure, diabetes, and other psychosocial covariables. A higher BMI at baseline was also associated with a higher cognitive decline at follow-up, after adjustment for the above-cited confounding factors. This association was significant for word-list learning. For the changes in scores at word-list learning (delayed recall), regression coefficients were -0.008 +/- 0.13, -0.09 +/- 0.13, -0.17 +/- 0.14, and -0.35 +/- 0.14 (p for trend < 0.001) for the second, third, fourth, and fifth quintiles of BMI at baseline when compared with the first quintile. No significant association was found between changes in BMI and cognitive function.

CONCLUSIONS: Body mass index was independently associated both with cognitive function (word-list learning and Digit-Symbol Substitution Test) and changes in word-list learning in healthy, nondemented, middle-aged men and women.