Objective To examine the incidence of hypoglycemic coma in children with insulin-dependent diabetes mellitus (IDDM) over 8 yr from 1981 to 1988 and to investigate the importance of residual β-cell function of HbA₁ levels and other variables as risk factors for hypoglycemic coma.

Research Design and Methods The study consisted of 155 children with IDDM aged < 16 yr at study entry. Mean age at onset of diabetes was 7.9 yr (range 1.1–15.6 yr). We made a prospective assessment of hypoglycemic coma episodes, with a standardized questionnaire, over a total observation time of 816.6 person-yr. Three monthly clinical and laboratory examinations, which included determinations of C-peptide and HbA₁ levels, were conducted. We compared children with hypoglycemic coma (cases) with children without hypoglycemic coma (controls) in a case-control analysis matched for diabetes duration. Yearly incidence of hypoglycemic coma, calculated as the number of subjects having an attack in 1 yr divided by the cumulative number of person-years for that year, was measured. Univariate and multivariate odds ratios were calculated from logistic regression.

Results Over the first 4 yr, the average yearly incidence was 4.4/100 person-yr compared with 7.4/100 person-yr during the later 4 yr (P < 0.0001). This tendency was accompanied by intensification of insulin treatment with an increase in the mean number of daily injections and a decrease in mean HbA₁ levels. In the case-control analysis, absent residual β-cell function was the most important risk factor for hypoglycemic coma (adjusted odds ratio 7.8, 95% confidence intervals 2.0–31.2), followed by near-normal HbA₁ levels (adjusted odds ratio 4.5, 95% confidence intervals 1.9–10.5).

Conclusions In this group of children, improvement of glycemic control apparently led to an increase in the incidence of severe hypoglycemia. In children with recurrent hypoglycemic coma and undetectable C-peptide levels, it may be safer to aim for somewhat less tight glycemic control.