Changes in cognitive abilities over a 4-year period are unfavorably affected in elderly diabetic subjects: results of the Epidemiology of Vascular Aging Study

Abstract

Objective: To compare 4-year changes in cognitive performance among elderly subjects according to category of fasting blood glucose (FBG) using American Diabetes Association criteria.

Research design and methods: Subjects without any detectable cognitive dysfunction were selected from the Epidemiology of Vascular Aging (EVA) Study, a cohort of community-dlwelling people aged 59-71 years at baseline. They were classified into glucose categories (normal, impaired fasting glucose [IFG], or diabetic) based on FBG values or known diabetes. Their cognitive abilities were assessed by a global test (Mini Mental Status Examination [MMSE]) and eight domain-specific tests, and they were reassessed 4 years later. Serious cognitive worsening was defined as a score evolution into the worst 15% of the sample's distribution of score differences (4-year score minus baseline score) for each test.

Results: At baseline, age-, sex-, and education-adjusted scores for all cognitive tests except one were similar across glucose categories. After 4 years, diabetic subjects had a lower performance on all tests except the MMSE, with differences reaching statistical significance on four tests. Adjusted odds ratios for serious worsening over 4 years in diabetic subjects, with reference to normal subjects, were >2 for four tests (P < 0.05) and bordering this value for two others (P < 0.09). Further adjustment for blood pressure or potential cognition-affecting substances (alcohol, tobacco, and medications) did not modify these results.

Conclusions: Despite similar high initial cognitive function, diabetic subjects tended to have an unfavorable evolution of cognitive performance over 4 years compared with subjects who had normal glucose or IFG.