Total and cause-specific mortality by elevated transferrin saturation and hemochromatosis genotype in individuals with diabetes: two general population studies.

OBJECTIVE Mortality is increased in patients with hereditary hemochromatosis, in individuals from the general population with increased transferrin saturation (TS), and also in patients with type 1 diabetes and increased TS from a highly specialized diabetes clinic. Thus, we have recommended targeted screening for TS in specialized diabetes clinics. Whether mortality is also increased in individuals from the general population with diabetes and increased TS is unknown. RESEARCH DESIGN AND METHODS In two Danish population studies (N = 84,865), we examined mortality according to baseline levels of TS and hemochromatosis genotype (HFE) G → A substitution at nucleotide 845 in codon 282 (C282Y/C282Y) in individuals with diabetes (type 1, N = 118; type 2, N = 3,228; total, N = 3,346). RESULTS The cumulative survival rate was reduced in individuals with diabetes with TS ≥50% vs. <50% (log-rank; P < 0.0001), with median survival ages of 66 and 79 years, respectively. The hazard ratio (HR) for TS ≥50% vs. <50% was 2.0 (95% CI 1.3-2.8; P = 0.0004) for total mortality overall (and similar for men and women separately); 2.6 (1.3-5.4; P = 0.008) for neoplasms; and 3.4 (2.0-6.0; P = 0.00002) for endocrinological causes. A stepwise increased risk of total mortality was observed for stepwise increasing TS (log-rank test, P = 0.0001), with an HR for TS ≥70% vs. TS <20% of 4.8 (2.0-12; P = 0.0006). The HR for total mortality in individuals with diabetes for C282Y/C282Y versus wild type/wild type was 3.3 (1.04-10; P = 0.04), and for C282Y/C282Y and TS ≥50% versus wild type/wild type and TS <50% was 6.0 (1.5-24; P = 0.01). Six percent of these premature deaths can possibly be avoided by early screening for TS or HFE genotype. CONCLUSIONS Individuals with diabetes, ascertained in the general population, with increased TS or HFE genotype have a twofold to sixfold increased risk of premature death.