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

Introduction: 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.