To determine the independent effects of obesity on cognitive performance and to examine interactions between obesity and non-insulin dependent diabetes mellitus (NIDDM).

Using a prospective design, male (n=551) and female (n=872) participants of the Framingham Heart Study were classified as obese (yes/no), diabetic (yes/no), and the number of diabetes-years was determined by data collected over an 18-year surveillance period. All subjects were free from dementia, stroke, and clinically diagnosed cardiovascular disease up to the time of cognitive testing. Statistical models were adjusted for age, education, occupation, native language, and cardiovascular disease risk factors. Body mass index status (non-obese or obese) and NIDDM status (diabetic/non-diabetic) were related to cognitive performance on multiple cognitive measures.

Adverse effects of obesity on cognitive performance were observed for men only. Diabetes-years related to poorer cognitive performance, but only when men and women were combined for analyses. Neither diabetes nor diabetes-years by obesity interactions were observed.

The gender-specific results for obesity, but not for diabetes, suggests that the underlying mechanisms linking them to cognition may be different.