Background: The assessment of cognitive function is of great importance in the management of elderly patients with diabetes mellitus. The purpose of the present study was to examine the effects of glucose control and asymptomatic cerebral infarction on impaired cognitive function in elderly patients with diabetes mellitus.
Methods: Two hundred and thirteen elderly diabetic patients (59 men, 154 women) with a mean age of 75 years; and 40 non-diabetic subjects participated in this study and underwent both brain magnetic resonance imaging (MRI) and several domains of cognitive function tests. Based on the brain MRI findings and neurological deficits, the subjects were divided into four groups: (i) the symptomatic cerebral infarction (CI) group; (ii) the asymptomatic CI group; (iii) the diabetic control group without any CI; and (iv) the non-diabetic control group. Cognitive function was assessed using the mini-mental state examination (MMSE), and the subtests of Wechsler Adult Intelligence Scale – Revised (WAIS-R) (the digit symbol test, the backward digit span test, the similarities test, and the picture arrangement test). Attention/complex psychomotor skill and visual memory were assessed with the digit symbol substitution test, the Stroop test, and the Benton visual retention test.
Results: Attention/complex psychomotor skill and visual memory were more impaired in the diabetic control group without any CI than in the non-diabetic control group. The asymptomatic and symptomatic CI groups were significantly inferior to the non-diabetic and diabetic controls in the digit symbol substitution test and Stroop test. The degree of cognitive impairment significantly correlated to the presence and number of small-sized cerebral infarction, but to a less degree, large-sized infarction. Multivariate analysis revealed that age, HbA1c, and cerebral infarction on MR images were independently associated with the impairment of complex psychomotor skill in patients with diabetes mellitus.
Conclusions: The presence of asymptomatic cerebral infarction on brain MR images as well as hyperglycemia could explain the impairment of attention/complex psychomotor skill and visual memory in elderly patients with diabetes mellitus.