Cognitive function and mood after profound nocturnal hypoglycaemia in prepubertal children with conventional insulin treatment for diabetes.

OBJECTIVES To examine the frequency of nocturnal hypoglycaemia, and the effects on cognitive function and mood, in children with insulin dependent diabetes mellitus (IDDM). DESIGN Two overnight glucose profiles, in the home environment, and assessments of cognitive function and mood the following day. Twenty nine prepubertal patients with IDDM (median age, 9.4 years; range, 5.3-12.9) and 15 healthy controls (single overnight profile), median age 9.5 (range, 5.6-12.1) years were studied. RESULTS Asymptomatic hypoglycaemia (glucose < 3.5 mmol/l) was observed in 13 of 29 patients studied on night 1: four of these and seven others were hypoglycaemic on night 2. The median glucose nadir was 1.9 (range, 1.1-3.3) mmol/l and the median duration of hypoglycaemia was 270 (range, 30-630) minutes. Hypoglycaemia was related to insulin dose, but not glycosylated haemoglobin (HbA1c) values, and was partially predicted by a midnight glucose of < 7.2 mmol/l. Cognitive performance was not altered after hypoglycaemia but a lowering of mood was observed. CONCLUSIONS Young children on conventional insulin regimens are at high risk for profound, asymptomatic nocturnal hypoglycaemia, which is difficult to predict. There was no short term effect on cognitive function but mood change was detected.