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 beta-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 less than 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 less than 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 beta-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.