Aims/hypothesis: Immigration studies can shed light on diabetes pathogenesis and risk factors. To this end, we investigated the association between age at immigration and diabetes occurrence at adolescence among immigrants to Israel.
Methods: We analysed cross-sectional data on 2,721,767 Jewish adolescents assessed for mandatory military service at approximately 17 years of age between 1967 and 2014. The study population comprised 430,176 immigrants with origins in Ethiopia, former USSR, Middle East and North Africa (ME/NA) and western countries. ORs for diabetes were calculated for men and women, grouped according to age at immigration, with Israel-born participants as controls. Unadjusted and fully adjusted models were made to account for possible confounders. Additionally, the study population was stratified by origin and each immigrant group was referenced to Israel-born participants of the same origin.
Results: There was a graded decrease in OR for diabetes across the study groups in the fully adjusted model. Immigrants arriving at age 0-5 years had comparable OR for diabetes to the Israeli-born reference group; those arriving at age 6-11 years had an OR of 0.82 (95% CI 0.70, 0.97; p = 0.017) and recent immigrants, arriving at age 12-19 years, had the lowest OR of 0.65 (95% CI 0.54, 0.77; p < 0.0001). When age at immigration was treated as a continuous variable, there was an adjusted risk for occurrence of diabetes of 0.97 (95% CI 0.96, 0.99; p = 0.001) for every year increment. The lower risk for diabetes among recent immigrants persisted in the unadjusted model and persisted when the study sample was stratified by sex and origin, except for immigrants arriving from ME/NA. Notably, Ethiopians born in Israel had a sixfold higher diabetes crude prevalence than Ethiopian immigrants arriving after the age of 5 years.
Conclusions/interpretation: Immigrants of different ethnic groups arriving earlier in childhood lose their protection against diabetes at adolescence, relative to children born in Israel. This is perhaps due to environmental and lifestyle changes, especially those beginning at an early age.
Keywords: Adolescent; Childhood; Diabetes mellitus; Environmental exposure; Ethnic groups; Immigration and emigration; Lifestyle; Pathogenesis; Risk factors.