Epidemiological aspects of the natural history of childhood diabetes.

Abstract

Studies in identical twins have shown only a 50% concordance for type 1 diabetes, indicating that environmental factors are of major importance. Prospective studies in twins and siblings of type 1 diabetics provide evidence of a long prediabetic phase. Environmental factors, inducing a pathological immune response in genetically susceptible individuals, may thus act long before the clinical onset. In Sweden a high and increasing incidence of childhood diabetes has been shown, with peak incidence rates at puberty in both boys and girls. The incidence rate is higher for boys than for girls. Significant geographical and seasonal variations are clearly indicated. The epidemiology of lost beta-cell function shortly after clinical onset differs significantly from the epidemiology of clinical onset as to sex and geographical and seasonal distribution. Environmental factors that affect the clinical onset of type 1 diabetes may thus differ from factors affecting the beta-cell function after onset. Factors affecting the peripheral insulin sensitivity should therefore be taken into consideration also when discussing the natural history of type 1 diabetes.