Is diabetes associated with cognitive impairment and cognitive decline among older women?

Background: The long-term effect of type 2 diabetes on cognitive function i s uncertain. Objective: To determine whether older women with diabetes have an increased risk of cognitive impairment and cognitive decline. Design: Prospective cohort study. Setting: Four research centers in the United States (Baltimore, Md; Portlan d, Ore; Minneapolis, Minn; and the Monongahela Valley, Pennsylvania). Participants: Community-dwelling white women 65 years and older (n = 9679). Measurements: Physician-diagnosed diabetes and other aspects of health hist ory were assessed by interview. Three tests of cognitive function, the Digi t Symbol test, the Trails B test, and a modified version of the Mini-Mental State Examination (m-MMSE), were administered at baseline and 3 to 6 years later. Change in cognitive function was defined by the change in the score for each test. Major cognitive decline was defined as the worst 10th perce ntile change in the score for each test. Results: Women with diabetes (n = 682 [7.0%]) had lower baseline scores tha n those without diabetes on all 3 tests of cognitive function (Digit Symbol and Trials B tests, P<.01; m-MMSE, P =.03) and experienced an accelerated cognitive decline as measured by the Digit Symbol test (P<.01) and m-MMSE ( P =.03). Diabetes was also associated with increased odds of major cognitiv e decline as determined by scores on the Digit Symbol (odds ratio = 1.63; 9 5% confidence interval, 1.20-2.23) and Trails B (odds ratio, 1.74; 95% conf idence interval, 1.27-2.39) tests when controlled for age, education, depre ssion, stroke, visual impairment, heart disease, hypertension, physical act ivity, estrogen use, and smoking. Women who had diabetes for more than 15 y ears had a 57%;, to 114% greater risk of major cognitive decline than women without diabetes. Conclusion: Diabetes is associated with lower levels of cognitive function and greater cognitive decline among older women.