Increasing incidence of type 1 diabetes in children with non-diabetic parents may partly be explained by increasing prevalence of maternal overweight/obesity.

ObjectiveTo investigate the trends and the risk of developing type 1 diabetes in the offspring of Swedes and immigrants by specific parental migration background, age, sex and birth cohort.DesignRegistry-based cohort study.SettingUsing Swedish nationwide data we analysed the risk of developing type 1 diabetes in 3 457 486 female and 3 641 304 male offspring between 0 and 30 years of age, born to native Swedes or immigrants and born and living in Sweden between 1969 and 2009. We estimated incidence rate ratios (IRRs) with 95% CIs using Poisson regression models. We further calculated age-standardised rates (ASRs) of type 1 diabetes, using the world population as standard.ResultsWe observed a trend of increasing ASRs among offspring below 15 years of age born to native Swedes and a less evident increase among offspring of immigrants. We further observed a shift towards a younger age at diagnosis in younger birth cohorts in both groups of offspring.Compared with offspring of Swedes, children (0–14 years) and young adults (15–30 years) with one parent born abroad had an overall 30% and 15–20% lower IRR, respectively, after multivariable adjustment. The reduction in IRR was even greater among offspring of immigrants if both parents were born abroad. Analysis by specific parental region of birth revealed a 45–60% higher IRR among male and female offspring aged 0–30 years of Eastern Africa.ConclusionsParental country of birth and early exposures to environmental factors play an important role in the aetiology of type 1 diabetes.

We found a lower IRR of T1DM among offspring to immigrants, but especially among young immigrants compared with Sweden-born individuals. The findings show that environmental factors are important in the etiology of T1DM.

OBJECTIVEThe risk for type 1 diabetes mellitus (T1DM) is increased in the second compared with the first generation of immigrants in Sweden. We investigated the effect of the mother's duration of stay in Sweden on the risk of T1DM in the offspring. RESEARCH DESIGN AND METHODSUsing data from national registries, we identified all subjects with T1DM among 984,798 children born in Sweden (aged 0-18 years) between 1992 and 2009. Incidence rate ratios (IRRs) with 95% CI were estimated using Poisson regression. RESULTSOffspring of mothers living in Sweden for up to 5 years had a 22% lower risk of T1DM (adjusted IRR 0.78, 95% CI 0.63-0.96) compared with offspring of mothers living in Sweden for 11 years or more. The risk increased with the mother's duration of stay in Sweden. CONCLUSIONSOur findings support the hypothesis that immigration to Sweden is associated with exposure to new environmental factors that contribute to the development of T1DM in genetically susceptible individuals.