Type II Diabetes and Cognitive Function: A population-based study of Native Americans

OBJECTIVE To explore the relationship between type II diabetes and cognitive function in older Native Americans and to assess the effects of other selected risk factors for cognitive dysfunction on this relationship.

RESEARCH DESIGN AND METHODS Cognitive function was assessed in 80 diabetic and 81 nondiabetic Native Americans who were 45–76 years of age in a cross-sectional population-based sub-study of the Strong Heart Study. Thirteen cognitive function tests were administered during a personal interview. Information about six other risk factors for cognitive dysfunction, including depressive symptoms, physical function, alcoholism, current alcohol use, hypertension, and myocardial infarction, was ascertained from interviews andfrom abstraction of medical records.

RESULTS Diabetes was associated with impairment on only two tests of cognitive function: verbal fluency (P = 0.004) and similarities (P = 0.010). Depressive symptoms were related to verbal fluency (P = 0.004), but did not explain thediabetes-related difference in performance. The effects of hypertension, depressive symptoms, and current alcohol use explained the diabetes-related performance difference on similarities. Cognitive function was not related to metabolic control (HbA_1c level).

CONCLUSIONS We found little evidence that type II diabetes in this population of Native Americans is associated with decrement in cognitive function. Some of the cognitive impairment previously attributed to diabetes may be related, at least in part, to the influence of other risk factors. This should be considered in the design of future studies in other populations.