The characteristic of cognitive function in Type 2 diabetes mellitus

To identify characteristics of neuropsychological function among elderly individuals with Type 2 diabetes mellitus with mild cognitive impairment (T2DM-MCI) and evaluate domain-specific effects of T2DM on cognition.

This was a cross-sectional study conducted in Tianjin, China. MCI subjects (n=246) and controls were identified in elderly individuals with diabetes, and groups were matched in a 1:1 ratio for sex, age and educational level. Cognitive function was assessed using WAIS-III (block design, digit span), Trail Making Test A, Trail Making Test B, WMS-III (word list learning, logical memory), verbal fluency and MMSE. We used multivariable logistic regression to find diabetic factors associated with MCI.

The mean MMSE score was 22.73 ± 2.32 in subjects with T2DM-MCI, versus 26.71 ± 2.43 in subjects cognitive normal (P<0.001). Executive and visuospatial functions were more impaired in individuals with T2DM-MCI than in those without, as assessed using block design (P<0.001), digit span test (P<0.001), and Trails B (P<0.001). For memory, subjects with T2DM-MCI did worse than those cognitive normal on the word learning list delayed recall (P=0.015). Diabetic-related factors such as longer duration of T2DM, higher HbA1c, insulin treatment was associated with a lower level of cognitive functioning using MMSE, block design, delayed recall and Trails B test.

T2DM should be considered a risk factor for MCI. This risk may be associated with duration of diabetes, use of glucose-lowering medications, degree of glucose control. To decrease risk of MCI, it is important to monitor glucose control and adjust medications appropriately in elderly patients.