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 eff ects on cognitive function and mood, in children with insulin dependent dia betes mellitus (IDDM). Design-Two overnight glucose profiles, in the home environment, and assessm ents of cognitive function and mood the following day. Twenty nine prepuber tal patients with IDDM (median age, 9.4 years; range, 5.3-12.9) and 15 heal thy controls (single overnight profile), median age 9.5 (range, 5.6-12.1) y ears were studied. Results-Asymptomatic hypoglycaemia (glucose < 3.5 mmol/1) was observed in 1 3 of 29 patients studied on night 1: four of these and seven others were hy poglycaemic on night 2. The median glucose nadir was 1.9 (range, 1.1-3.3) m mol/1 and the median duration of hypoglycaemia was 270 (range, 30-630) minu tes. Hypoglycaemia was related to insulin dose, but not glycosylated haemog lobin (HbAlc) values, and was partially predicted by a midnight glucose of < 7.2 mmol/1. Cognitive performance was not altered after hypoglycaemia but a lowering of mood was observed. Conclusions-Young children on conventional insulin regimens are at high ris k for profound, asymptomatic nocturnal hypoglycaemia, which is difficult to predict. There was no short term effect on cognitive function but mood cha nge was detected.