Iron, hemochromatosis genotypes, and risk of infections: a cohort study of 142 188 general population individuals.

It is unclear whether risk of infection is increased in individuals with hereditary hemochromatosis and in individuals with low or high plasma iron, transferrin saturation, or ferritin. Therefore, we tested whether high and low iron, transferrin saturation, and ferritin are associated with risk of infections observationally and genetically through HFE genotypes. We studied 142 188 Danish general population individuals. Iron, transferrin saturation, and ferritin were measured in 136 656, 136 599, and 38 020 individuals, respectively. HFE was genotyped for C282Y and H63D in 132 542 individuals. Median follow-up after study enrollment was 8 years (range, 0-38) for hospital and emergency room admissions with infections (n = 20 394) using the National Patient Register, covering all Danish hospitals. Hazard ratios for any infection were 1.20 (95% confidence interval [CI], 1.12-1.28) and 1.14 (95% CI, 1.07-1.22) in individuals with plasma iron ≤5th or ≥95th percentile compared with individuals with iron from 26th to 74th percentiles. Findings for transferrin saturation were similar, whereas infection risk was not increased in individuals with ferritin ≤5th or ≥95th percentile. Hazard ratios in C282Y homozygotes vs noncarriers were 1.40 (95% CI, 1.16-1.68) for any infection, 1.69 (95% CI, 1.05-2.73) for sepsis, and 2.34 (95% CI, 1.41-3.90) for death from infectious disease. Risk of infection was increased in C282Y homozygotes with normal plasma iron, transferrin saturation, or ferritin, and in C282Y homozygotes without liver disease, diabetes, and/or heart failure. In summary, low and high plasma iron and transferrin saturation were independently associated with increased infection risk. C282Y homozygotes had increased risk of any infection, sepsis, and death from infections. Even C282Y homozygotes with normal iron, transferrin saturation, or ferritin, not currently recommended for genotyping, had increased infection risk.