Risk Factors For Cognitive Impairment In Type 2 Diabetes Mellitus Patients

Objective: To explore the relationship of type 2 diabetes to cognitive impairment. Methods: A hospital-based frequency matched case-control study was conducted. 118 type 2 diabetes mellitus (T2DM) patients were compared with 100 age, gender and level of education matched non-diabetic controls. Cognitive function of the subjects was assessed by the following cognitive tests: (1) Mini-Mental State Examination (MMSE);(2) Four cognitive tests from Wechsler Adult Intelligence Scale-Revised in China (WATS-RC), namely, Picture Completion Test, Digit Span Test, Digit Symbol Substitution Test and the Similarities Test;(3) Clinical Memory Scale (CMS). The anxiety and depression symptoms of the subjects were assessed using Hospital Anxiety and Depression Scale (HAD). The statistical differences of cognitive scores between case and control groups were examined with t-test. Chi-square test was used to examine the differences for variable's proportions.Results: The MMSE scores of case and control groups were 27.0±3.2 and 27.8±2.0 respectively, which had no statistical difference between two groups (t=1.668, P=0.098) . The scores of four WATS-RC tests were all significantly lower in the cases than those in the controls. The results indicate that the cases were likely to be cognitively impaired in several cognitive domains including logical and abstractive reasoning, memory, attention, processing and psychomotor speed. The mean memory quotient (MQ) of the case group was significantly lower than that of the control group(90.0±15.6 vsl00.3±12.8, t=5.354, P<0.001). Similarly, the mean MQ of the case group was also significantly lower than the mean of Norm, while no significant difference of MQ was found between control group and the Norm (t=0.251, P=0.803) . The scores of 5 memory tests fromCMS in the cases were all significantly lower than those in the controls, which suggested that the case group had impaired verbal memory and visuospatial memory. Both age groups ( below 5 5-years old group and 5 5-years or older group) and gender groups of the cases had poorer performance in a number of cognitive tests copmpared with the controls, which indicate that the cases in different age and gender groups have impaired cognitive function. The results of HAD showed that the scores of depression in the case group were higher than those in the control group.Conclusion: Results from the present study suggest that type 2 diabetes are associated with cognitive impairment in a number of cognitive domains including logical and abstractive reasoning, memory, attention, processing and psychomotor speed, verbal memory and visuospatial memory. Further studies on delineating the mechanisms of the observed associations are warranted.