THE ASSOCIATION OF NON-INSULIN-DEPENDENT DIABETES-MELLITUS AND COGNITIVE FUNCTION IN AN OLDER COHORT

OBJECTIVE: In this study, we examined the association of non-insulin-d ependent diabetes mellitus (NIDDM) and impaired glucose tolerance (IGT ) with cognitive function in a population-based sample of older indivi duals. RESEARCH DESIGN AND METHODS: Subjects were 1509 healthy, commun ity-dwelling men and women aged 55 years and older who were participan ts in the Rancho Bernardo Study and attended clinic visits in 1984-87 and in 1988-91. An oral glucose tolerance test was administered during the 1984-87 visits. Based on World Health Organization criteria, part icipants were classified into those with NIDDM, IGT, or normal glucose tolerance. During the 1988-91 clinic visits, 12 tests of cognitive fu nction were administered. RESULTS: Of the participants, 14.3% of the m en and 9.9% of the women had NIDDM, and 21.0% of the men and 28.0% of the women had IGT. Multiple regression analysis was used to compare th e cognitive function of individuals with NIDDM and IGT with individual s with normal glucose tolerance after adjustment for age, education, o besity, depression, blood pressure, and current estrogen use. In men, there were no statistically significant differences in any of the 12 c ognitive function tests by glucose tolerance category. Compared with t hose with normal glucose tolerance, women with IGT had lower scores on almost every cognitive function test, whereas women with NIDDM had hi gher scores, but none of these differences were statistically signific ant after adjustment for multiple comparisons. Futhermore, observed di fferences by NIDDM or IGT status were small and accounted for less tha n or equal to 0.6% of the explained variance in cognitive function. CO NCLUSIONS: This study shows no strong or consistent association betwee n IGT or mild diabetes with cognitive function in community-dwelling o lder adults.