Mortality from ischaemic heart disease: sex-specific effects of transferrin saturation, serum iron, and total iron binding capacity. The HUNT study

Background: We assessed sex-specific associations of iron status with ischaemic heart disease (IHD) mortality and explored whether the strength of the associations changed during follow-up. Design: Prospective cohort study. Methods: During 11.4 years of follow-up, IHD mortality was studied in 28,154 men and 32,644 women without known myocardial infarction or stroke at baseline. Results: During follow-up, 1,034 men and women died from IHD. Compared to being in the highest quartile of transferrin saturation, the multivariate adjusted hazard ratio associated with being in the lowest quartile was 1.3 (95% CI 1.0-1.6) in men and 1.4 (95% CI 1.0-1.9) in women. The corresponding hazard ratios for serum iron were 1.5 (95% CI 1.1-1.9) in men and 1.1 (95% CI 0.8-1.4) in women, and for total iron binding capacity (TIBC), the hazard ratio of being in the highest compared to the lowest quartile was 0.9 (95% CI 0.8-1.2) in men and 1.5 (95% CI 1.1-2.0) in women. Associations with iron status were stronger in the early than in later stages of follow-up. Conclusions: The results suggest that low iron status may be a late sign of IHD pathology or that unknown prevalent disease at baseline could influence the associations.