COGNITIVE FUNCTION IN YOUNGER TYPE-II DIABETES

OBJECTIVE - To examine central nervous system involvement as a possibl e complication of diabetes by performing a comprehensive neuropsycholo gical evaluation of relatively young (age < 55 years) NIDDM patients a nd a group of control subjects. RESEARCH DESIGN AND METHODS - A cross- sectional comparative study of 28 patients, with duration of diabetes 5-18 years (mean +/- SD 8.3 +/- 3.2 years), screened for acceptable gl ycemic control and absence of hypoglycemia on the day of examination, compared with 28 demographically similar, nondiabetic control subjects . Neuropsychometric tests performed were Mini-Mental Status Examinatio n (MMSE), Neurobehavioral Cognitive Status Examination (NCSE), and P30 0 latencies (endogenous evoked potentials). RESULTS - Seven (25.0%) pa tients reported history suggestive of cognitive impairment during day- to-day activities, and 17 (60.7%) had distal symmetrical polyneuropath y. Average P300 latencies were significantly delayed among the diabeti c patients compared with the control subjects (349.5 +/- 28.2 vs. 312. 9 +/- 19.3 ms; t = 5.68, P < 0.001). Although there was no significant difference in MMSE scores, compared with control subjects significant ly more patients had impairment in NCSE tests of attention (chi(2) = 7 .38, P < 0.01), repetition (chi(2) = 4.073, P < 0.05), and memory (chi (2) = 5.83, P < 0.05), while there was no significant difference in te sts of comprehension, naming, construction, and calculation. Duration of diabetes, HbA(1c) levels, and the presence of distal symmetrical po lyneuropathy among patients each did not correlate with any of the par ameters of cognitive function evaluated. Higher blood glucose levels d uring the electrophysiological testing were associated with less delay in P300 latencies among the patients. CONCLUSIONS - Central nervous s ystem impairment, manifesting as mild impairments in certain cognitive skills, should be recognized as a possible complication of longstandi ng NIDDM, even in relatively younger individuals.