A Study of Cognitive Dysfunctions in Type 2 Diabetes Mellitus

BACKGROUND Diabetes mellitus (DM) refers to a group of common metabolic disorders that share the phenotype of hyperglycaemia. The worldwide prevalence of DM has dramatically increased over the past 2 decades. The prevalence of DM increases with age from 0.19% in persons below 20 years to 20.1% in those above 65 years. Type 2 diabetes mellitus is known to produce macro vascular complications. Now compelling evidence is emerging about the effect of diabetes on the brain and resultant cognitive dysfunctions. Against this backdrop, we set out to study the cognitive dysfunctions in type 2 diabetes mellitus, since the presence of cognitive dysfunctions may adversely affect management of diabetes, which would have important clinical and public health implications. METHODS This is a cross sectional study done in a tertiary care teaching hospital. Institutional ethical committee approved the study. Informed consent was taken from the study participants. 30 in-patients with type 2 diabetes mellitus were matched against 30 non-diabetic controls. The sample was matched for age, gender, education and socio economic status. Demographic details of the subjects were collected using the socio-demographic and clinical data proforma designed especially for the study. The tools used were Standardized Mini Mental State Examination (SMMSE) and Brief Cognitive Rating Scale (BCRS). Data was analysed using Student's t-test, Chi-square test, ANOVA and Mann Whitney U test. RESULTS The mean score on SMMSE obtained by patients with type 2 diabetes was 24.26 while that obtained by comparator normoglycemic group was 28.06 and this difference was very highly significant (p value 0.001). However, the lower mean total score obtained by the diabetics on SMMSE (24.26), though statistically very significant with respect to the non-diabetic comparator group, was still within the normative data, which needs further analysis. In BCRS, very highly significant difference (p value 0.001) between the two groups was found with diabetics performing poorly in concentration, recent memory, past memory, and orientation domains while no significant difference was found in the functioning and self-care domain. Longer duration of type 2 diabetes led to poorer performance on SMMSE. This is reflected in the mean scores obtained by patients, with those with duration of illness greater than 10 years having a mean score of 23.77 while those with less than 5 years of type 2 DM achieving mean score of 27.36. Poorly controlled type 2 DM as indicated by higher HbA1c values affected SMMSE scores adversely with those with HbA1c greater than 10.3% getting a mean score of 23.63 compared to the mean score of 25.40 obtained by those with HbA1c of 6.3-8.3% and this was statistically highly significant. CONCLUSIONS Diabetics had significant cognitive dysfunction which accentuated further with longer duration of illness, elevated HbA1c levels, use of both Oral Hypoglycaemic Agents and Insulin and advancing age. However, the degree of cognitive dysfunctions did not endanger patient's ability to self-manage their illness.