Hemoglobin concentration and risk of arterial and venous thrombosis in 1.5 million Swedish and Danish blood donors.

To access publisher's full text version of this article click on the hyperlink belowIntroduction: There are conflicting results whether elevated hematocrit is associated with an increased risk of thromboembolic events in individuals without polycythemia vera. To assess the risk of vascular events in relation to hemoglobin concentration, we conducted a large population-based cohort study based on Scandinavian health registers. Materials and methods: We included 1,538,019 Swedish and Danish blood donors between 1987 and 2012. Hazard ratios (HRs) of arterial and venous thrombosis were estimated using Cox regression. Additionally, we fitted person-stratified models where each donor was compared only to him-/herself. Results: The risk of myocardial infarction and ischemic stroke increased with higher hemoglobin concentration in both men and women. The HRs for myocardial infarction and ischemic stroke in men with hemoglobin concentration ≥ 17.5 g/dL were 3.52 (95% confidence interval [CI], 2.85-4.36) and 2.36 (95% CI, 1.63-3.43), respectively, compared to the reference group. The corresponding HRs for women with hemoglobin concentration ≥ 16.0 g/dL were 3.22 (2.12-4.89) and 2.35 (1.37-4.02) for myocardial infarction and ischemic stroke, respectively. The risk of venous thrombosis was highest in men with subnormal hemoglobin concentration (