The number of adults with incident type 1 diabetes phenotype in Iceland is half the number in children – A population based study

Aims: Type1 diabetes is generally regarded as an abruptly presenting disease in children without family history. The incidence and prevalence of insulin requiring diabetes in adults is unclear. The aim of this study was to clarify this issue by examining the epidemiology of type 1 diabetes diagnosed in adulthood in a countrýs whole population. Methods: Complete clinical and prescription data were used to identify cases of insulin requiring diabetes in the Icelandic population 18 years and older during the decade preceding February 2013. Health care databases and the insulin reimbursement system allowed for near 100% ascertainment of cases. Results: Mean age at diagnosis was 32.1 years. The WHO age-adjusted incidence rate was 4.29/100.000 individuals and the point prevalence 0.10%. One fourth of cases were diagnosed after the age of forty. The male-to-female incidence rate ratio was 1.59. Almost 30% of cases presented with diabetic ketoacidosis and 40% had a positive family history. Conclusion: Type 1 like diabetes commonly presents in adults and family history is not rare. One can expect one case of type 1 diabetes in adults for every two children diagnosed. These results emphasize the need to acknowledge the possibility of absolute insulin deficiency in any newly presenting adult with diabetes.