Possible association of a reduction in cardiovascular events with blood donation

Background-The iron hypothesis suggests that females are protected from atherosclerosis by having lower iron stores than men, thus limiting oxidation of lipids. Objective-To test the iron hypothesis by comparing cardiovascular event rates in whole blood donors compared with non-donors. Design-Prospective cohort with telephone survey follow up. Setting-The State of Nebraska, USA. Participants-A sample was selected from the Nebraska Diet Heart Survey (NDHS) restricting for age greater than or equal to 40 years and absence of clinically apparent vascular diseases at time of enrollment in to NDHS (1985-87). Main outcome measures-The occurrence of cardiovascular events (myocardial infarction, angina, stroke), procedures (angioplasty, bypass surgery, claudication, endarterectomy), nitroglycerin use, or death (all cause mortality), and level of blood donation. Results-Participants were 655 blood donors and 3200 non-donors who differed in education, physical activity, diabetes, and frequency of antihypertensive treatment; 889 were lost to follow up. Sixty four donors and 567 non-donors reported cardiovascular events (crude odds ratio = 0.50, 95% confidence interval (CI) 0.38-0.66). The benefit of donation was confined to non-smoking males (adjusted odds ratio 0.67, 95% CI 0.45-0.99). Benefit was limited to current donors (the most recent three years). No additional benefit resulted from donating more than once or twice over three years. Conclusion-In support of the iron hypothesis, blood donation in non-smoking men in this cohort was associated with reduced risk of cardiovascular events. A randomised clinical trial is warranted to confirm these findings as the observed personal health benefit of donation has public policy ramifications.