Background: Vascular risk factors are blamed as being involved in the pathogenesis of cognitive dysfunction in the elderly. Alzheimer's disease or vascular-type dementia could be part of a metabolic syndrome. The aim of this study was to evaluate whether there is any relation between insulin resistance and cognitive status of the elderly regarding normal, mild cognitive impairment (MCI), Alzheimer's disease (AD), vascular dementia (VaD) and mixed dementia.

Methods: 267 elderly patients admitted to an outpatient geriatrics clinic were evaluated medically and cognitively in this study. The patients were diagnosed using ARDRA and DSM-IV criteria for AD; NINDS-AIREN and DSM-IV criteria for VaD; and Petersen criteria for MCI. Insulin resistance was calculated using both the homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) formulas.

Results: The mean values of HOMA and QUICKI scores were 2.79 (SD ± 3.56) and 0.346 (SD ± 0.036) for the normal group, 2.81 (SD ± 3.06) and 0.354 (SD ± 0.047) for AD group, 2.20 (SD ± 1.82) and 0.360 (SD ± 0.048) for VaD group, 2.87 (SD ± 1.81) and 0.339 (SD ± 0.038) for mixed dementia group, 2.79 (SD ± 2.81) and 0,349 (SD ± 0.042) for MCI group, respectively. There were no statistically significant differences between HOMA and QUICKI scores of all the groups.

Conclusion: This is the first study of the possible relation between insulin resistance and cognitive function in people categorized according to five forms of cognitive status. Unfortunately the results do not allow generalizations. Further prospective cohort studies that follow a normal cognitive group and MCI patients with and without insulin resistance are necessary.