Diabetes and cognitive function in a middle-aged cohort - Findings from the Whitehall II study

Objective: To compare cognitive performance in those with diabetes, impaired glucose tolerance, and normoglycemia in a middle-aged cohort. Methods: The authors analyzed data from a prospective occupational cohort study begun in 1985 - 1988 (baseline). Diabetes was classified from oral glucose tolerance tests that were performed in 1992 - 1993 (phase 3) and 1997 - 1999 (phase 5) and self reported diagnosis of diabetes from questionnaire at baseline, 1989 (phase 2), phase 3, 1995 (phase 4), and phase 5 of the study. A battery of cognitive tests (memory, Alice Heim 4 [AH 4], Mill Hill vocabulary test, phonemic fluency, and categorical fluency) were measured at phase 5 in 4,020 men and 1,627 women with a mean age of 56 and free of symptoms of stroke. Results: At phase 5, a total of 208 (5%) men and 101 (6%) women had diabetes while 405 (10%) men and 192 (12%) women had impaired glucose tolerance. Those with diabetes were at increased risk of poor performance in AH 4 compared to those without (men: OR, 2.45; 95% CI, 1.77 to 3.38; women: OR, 1.83; 95% CI, 1.09 to 3.08). These effects were independent of age, social position, vascular problems, and health- related behaviors. Impaired glucose tolerance was not related to any measure of cognition. Conclusions: Type 2 diabetes is associated with poor performance in some aspects of cognition in middle- aged men and women.