Event related P300 potential in NIDDM patients without cognitive impairment and its relationship with previous hypoglycemic episodes.

OBJECTIVES The purpose of this study was to evaluate the ERP P300 in non insulin dependent diabetes mellitus (NIDDM) patients without cognitive impairment and the relationship with clinical variables, the presence of retinopathy and previous hypoglycemic episodes. METHODS NIDDM patients (N=44) without evidence of cognitive impairment and controls (N=17) were studied clinically and with ancillary exams and the ERPs P300 were recorded. Patients were examined clinically and with the Folstein Mini-Mental Examination (MMSE) for cognitive function and all patients showed a score higher than 26 (maximal value=30). Previous hypoglycemia was evaluated through a questionnaire establishing the number of episodes and the symptoms of hypoglycemia in a scale scoring from zero to 15. RESULTS ERP P300 latencies were significantly higher in NIDDM patients than in controls (p<0.03). ERP P300 measures were significantly related to age (Pearson, p<0.01) and not to metabolic variables, disease duration or the presence of retinopathy. Severity of hypoglycemia was not associated to ERP P300 latency. CONCLUSIONS Our study supports the evidence that NIDDM patients, without signs of nervous system involvement, have ERP P300 alterations and this is not related to retinopathy, metabolic variables or previous hypoglycemic episodes. Chronic hyperglycemia may alter brain glucose transport and increase tolerance to hypoglycemia effects in the nervous system.