Cognitive impairment in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a modern day epidemic. Chronic course of diabetes is detrimental to the cognitive functions. To decipher the pattern of cognitive impairment in relation to the duration of diabetes. Cross-sectional. T2DM patients (Group I: ⩽5 years duration of diabetes, n = 11; Group II: >5 years duration of diabetes, n = 17) without clinical evidence of central nervous system damage and non-diabetic controls (n = 18) were studied clinically and P300 event-related potentials (ERPs) recorded using three stimuli oddball paradigm. Subjects were examined with Folstein mini-mental state examination (MMSE) for cognitive function and those showing scores more than 26 (maximum score = 30) were enrolled for the study. Patients with known diabetic complications were excluded. P300 latencies in diabetic group did not relate linearly to the duration of diabetes. Diabetic subgroups with ⩽5 years and >5 years duration of diabetes showed striking differences, patients with over 5 years of disease duration had much prolonged P300 latencies in contrast to patients with 5 years or less disease duration who showed trends similar to that of control group. Differences in P300 amplitudes between groups were non-significant. Hypertensive diabetics showed much prolongation in P300 latencies compared to normotensive diabetics. P300 ERPs revealed cognitive dysfunction which was not detected by neuro-psychometric test (MMSE). Patients with T2DM have decreased cognitive function which is more prominent when the disease duration exceeds 5 years. Co-existence of hypertension with T2DM further increases the risk of cognitive impairment.