COGNITIVE FUNCTION IN PATIENTS WITH INSULIN-DEPENDENT DIABETES-MELLITUS DURING HYPERGLYCEMIA AND HYPOGLYCEMIA

BACKGROUND: To determine the impact of glycemic control, gender, and o ther relevant parameters on cognitive function during exposure, to dif ferent blood glucose levels in patients with insulin-dependent diabete s mellitus (IDDM), we examined neuropsychologic function during experi mentally induced periods of hyperglycemia and hypoglycemia. METHODS: W e studied 20 men and 22 women, aged 18 to 44 years, with IDDM duration of 3 to 14 years and HbA1 values ranging from 5.8% to 18.0% (nondiabe tic range 5.4% to 7.4%). We used a controlled experimental setting inv olving tests of sensory perceptual processing, simple motor abilities, attention, learning and memory, language, and spatial and constructio nal abilities at plasma glucose levels of 2.2, 5.6, 8.9, 14.4, and 21. 1 mmol/L. Patients were blind to the glucose level. Tests used at each glucose level included reaction time (simple and choice), digit vigil ance, trail making part B, word recall, digit sequence learning, and v erbal fluency. RESULTS: All aspects of neuropsychologic function were diminished at 2.2 mmol/L when compared with basal levels of performanc e at 8.9 mmol/L, whereas no alterations were observed at 14.4 or 21.1 mmol/L. Tests involving associative learning, attention, and mental fl exibility were the most affected during hypoglycemia. Glycemic control was not correlated with neuropsychologic function at any glucose leve l. Women demonstrated less of an impairment in neuropsychologic functi on than men at 2.2 mmol/L. CONCLUSIONS: Cognitive function in IDDM pat ients was generally well-preserved even at substantially elevated bloo d glucose levels. Deficits in all relevant areas of cognitive function occurred during hypoglycemia (2.2 mmol/L), irrespective of prior glyc emic control, and women with IDDM were less cognitively impaired than men with IDDM during hypoglycemia.