Diabetes as a predictor of change in cognitive functioning among older mexican americans – a population-based cohort study

PURPOSE: We performed a longitudinal analysis with repeated measurements between 1999 and 2001 to evaluate the impact of diabetes on changes in cognitive function among older Mexican Americans over a 2-year period. METHODS: Study subjects were derived from an existing cohort of Mexican Americans aged 60 and over in the Sacramento Area Latino Study on Aging (SALSA) project. Diabetes was diagnosed on the basis of history, medication use, and fasting plasma glucose level. Cognitive functioning was measured by the Modified Mini Mental State Exam (3MS) and Delayed Word-list Recall Test. Data analysis was conducted using a generalized estimating equation (GEE). RESULTS: Among the 1,789 SALSA participants, 585 (33%) had diabetes at baseline. Diabetic subjects had lower baseline cognitive score than non-diabetic subjects (3MS: MEAN = −1.65, P = 0.003; word-list test: MEAN = −0.38, P = 0.005). The rate of decline in the cognitive score over 2 years among diabetic subjects was greater than that of the non-diabetic subjects (3MS: MEAN = −0.52, P = 0.26; word-list test: MEAN = −0.08, P = 0.42), when adjusted for age, gender, education, depression, household income, and hypertension. A sensitivity test for major cognitive decline (defined as the worst 10th percentile change from initial to 2nd follow-up score) showed a significant difference in cognitive functioning between the two groups [3MS: RR = 1.69, 95% CI (1.22, 2.35); word-list test: RR = 1.57, 95% CI (1.00, 2.23)]. The effect of diabetes on changes in cognitive functioning was significantly modified by the presence of stroke (change in 3MS: diabetes ONLY = −1.51, stroke ONLY = −3.55, diabetes and STROKE = −7.72; change in word-list test: diabetes ONLY = −0.36, stroke ONLY = −0.78, diabetes and STROKE = −1.45) CONCLUSION: Diabetes appeared to be a predictor of cognitive impairment among older Mexican Americans. The association of diabetes and cognitive impairment was modified by the presence of stroke. Further research focusing on a long-term impact of diabetes is warranted.