Onset mortality of type I diabetes in 0 to 19‐year‐old children in The Netherlands, 1988‐1990

After the introduction of insulin therapy by Banting and Best in 1922, the mortality rate associated with type I diabetes decreased dramatically (1). However, some patients with type I diabetes die at the onset of the disease. The aim of the present study was to determine the onset mortality of young diabetic individuals in The Netherlands in 1988-1990, and to compare the results with those of the first diabetes mortality study in the Netherlands for the period 19781980 (2). The study was based on the nationwide populationbased register of mortality data of The Netherlands Central Bureau of Statistics. This register monitors issues of death certificates and uses the ninth revision of the International Classification of Diseases in determining the underlying cause of death. For the years 19881990 all 019-year-old deaths with diabetes mellitus as the primary or secondary cause of death (ICD9 code: 250) were obtained. To check the comprehensiveness of these data, mortality data from the SIC Health Care Information were also obtained. This is a different and independent database which contains only information on hospitalized patients. For those who die at home there is no other independent database. As it is possible that children died at home because of unrecognized diabetes mellitus and were classified with hypertonic dehydration (ICD 276.0), acidosis (276.2) and dehydration (276.5) as the primary cause of death, we also obtained data from The Netherlands Central Bureau of Statistics for children who died at home with these diagnoses. To determine onset of death, supplementary data were obtained by means of a questionnaire sent to physicians in charge. To calculate the onset death rate incidence (mortality risk), data from the second nationwide incidence study in The Netherlands were used (3). The 95% confidence limits were calculated using Poisson distribution. The methods of data collection, and statistical calculations, were the same as in the first study (the mortality study as well as for the nationwide incidence study of type I diabetes among children less than 20 years of age (2,3)). Diabetes mellitus appeared as an underlying (primary) or contributing (secondary) cause of death on the death certificate in 12 cases. All children identified by the SIC Health Care Information who died in hospital with the main diagnosis diabetes mellitus were also identified by The Netherlands Central Bureau of Statistics by the death certificate. In the search for possible unrecognized cases of diabetes mellitus, we found no patient who died at home with one of the related diagnoses mentioned above. Supplementary data were obtained from all physicians. These data showed that three patients died at onset: two girls aged 1 year and 19 years, and one boy aged 13 years. Both girls died in hospital while the boy died at home. All three children had diabetic ketoacidosis. In 1978-1980, 11 children died at onset. The total number of patients (0-19 years) who died at onset in 1988-1990 was significantly lower than in 1978-1980 (Fisher exact test p < 0.05). The mortality risk in 1978-1980 was 0.75 (11 of 1464 newly diagnosed patients, 95% confidence interval (CI) 0.38-1.34) and in 1988-1990 0.20 (3 of 1527 newly diagnosed patients, 95% CI 0.04-0.57). Because of the small number of onset deaths the confidence intervals overlapped. The quality and reliability of death certificate statistics in diabetes mortality studies are being questioned. Diabetes mellitus is a disease with certification and coding problems, as it is often difficult to determine whether diabetes was the cause of death or only contributed to it. Therefore, we obtained supplementary data from physicians who completed the death certificates. As all of the physicians responded and because of the 100% agreement with data from the hospital recordings, our data are complete and reliable for all hospital deaths. Of the 11 children who died at onset in 1978-1980, 9 died in hospital and 2 at home; in 1988-1990 2 died in hospital and 1 at home. In both periods the individuals who died had diabetic ketoacidosis. The period before a diagnosis of diabetes mellitus is established is a vulnerable one for the patients as they or their parents are unaware of their disease and of the significance of the symptoms. They might develop ketoacidosis, one of the main causes of increased risk of death. Especially difficult is it to recognize the symptoms in very young children, similar to the 1year-old-girl in our study. Factors such as improved physician and patient knowledge, earlier recognition of the disease, earlier start of treatment, and improvement in care and treat-