Insulin resistance and executive dysfunction in older persons

OBJECTIVES: To evaluate the association between insulin resistance (IR) and executive dysfunction in a large, population-based study of older persons without diabetes mellitus (DM) or dementia. DESIGN: Cross-sectional study. SETTING: Outpatient clinic in Greve in Chianti and Bagno a Ripoli, Italy. PARTICIPANTS: A total of 597 subjects aged 65 to 93 without DM or dementia. MEASUREMENTS: Anthropometric measurements; plasma fasting levels of glucose, insulin, cholesterol (total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol), and insulin-like growth factor-1 (IGF-I); homeostasis model assessment (HOMA) to estimate degree of IR; Trail Making Test (TMT) A; TMT-B; TMT-B minus TMT-A (DIFF B-A); and Mini-Mental State Examination (MMSE). RESULTS: IR (HOMA) was associated with longer TMT-B (correlation coefficient (r) = 0.11; P = .006) and DIFF B-A times (r = 0.10; P = .022). Subjects in the upper tertile of IR were older and had longer TMT-B and DIFF B-A than participants in the lowest tertile. After adjusting for age, sex, and years of formal education, IR was significantly correlated with TMT-A, TMT-B, and DIFF B-A. After adjusting for age, sex, education, body mass index, waist:hip girth ratio, HDL-C, triglycerides, IGF-1, hypertension, drug intake, and physical activity, the results did not significantly change. After introducing MMSE score into the model, IR continued to be an independent determinant of TMT-A (β = 11.005; P =.021), TMT-B (β = 28.379; P