Background: The global rise in incidence of type 1 diabetes (T1D) is too rapid to be attributed to susceptible genetic background, pinpointing a significant role for environmental factors. Unlike the theory that the need for genetic susceptibility has lessened over time, we hypothesized that the rise in T1D incidence is faster in a genetically susceptible population.
Subjects and methods: The study population comprised of 5080 patients aged 0 to 17 years who were reported to the National Israel Diabetes Registry between 1997 and 2014. The patients were divided into familial cases (first-degree relative has T1D), and sporadic cases. Demographic and clinical data were retrieved from the registry. The change in annual percent (from the entire cohort) was computed separately for the sporadic and familial cohorts.
Results: The familial (n = 546; 10.7%) and sporadic (n = 4534; 89.3%) cases were comparable for gender, ethnicity, and age at diagnosis. Consanguinity was more common in the familial vs sporadic group (10% vs 6.1%; P = .001). The average annual percent change increased by 1.9% in the familial cases and decreased by 0.2% in the sporadic cases (P = .04).
Conclusions: The rapid rise in the proportion of familial cases of T1D suggests that environmental factors impose higher diabetogenic pressure in patients with a susceptible genetic background.
Keywords: familial; incidence; registry; sporadic; type 1 diabetes.
© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.