The risk of hemochromatosis among first- and second-generation immigrants: a cohort study of the total population in Sweden

Purpose: We aimed to analyze the risk of hereditary hemochromatosis (HH) among first-generation and second-generation immigrants in Sweden using Swedish-born individuals and Swedish-born individuals with Swedish-born parents as referents, respectively. Methods: All individuals aged 18 years of age and older, n = 6,180,500 in the first-generation study, and n = 4,589,930 in the second-generation study were included in the analyses. HH was defined as at least one registered diagnosis International Classification of Diseases 10th edition (E83.1) in the National Patient Register between January 1, 1998 and December 31, 2018. Cox regression was used to estimate the hazard ratios (HRs) with 99% confidence intervals (CI) owing to multiple testing, of incident HH with adjustments for age, cancer, other comorbidities, and socio-demographics. Results: In the first-generation study, there were 5,112 cases of HH, and in the second-generation study 4,626 cases of HH. The adjusted HRs for first-generation men and women overall were 0.72 (99% CI: 0.63–0.82) and 0.61 (99% CI: 0.52–0.72), respectively, and for the second-generation men and women 0.72 (99% CI: 0.62–0.83) and 0.97 (99% CI: 0.83–1.14), respectively, with a higher risk found only among first-generation men from Western Europe, HR 1.47 (99% CI: 1.05–2.06), compared to the control group. Conclusions: Our findings indicate that the overall risk of HH was lower among both first-generation and second-generation immigrants when compared to individuals born in Sweden or with Swedish-born parents. An elevated risk for HH was observed exclusively among first-generation men originating from Western Europe. These findings represent new knowledge and should be of global interest.