Journal of the National Cancer Institute Advance Access originally published online on April 8, 2008
JNCI Journal of the National Cancer Institute 2008 100(8):572-579; doi:10.1093/jnci/djn084
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© The Author 2008. Published by Oxford University Press.
ARTICLES |
Donation Frequency, Iron Loss, and Risk of Cancer Among Blood Donors
Affiliations of authors: Departments of Medical Epidemiology and Biostatistics (GE, MR, TNT, JA, ON) and Medicine, Clinical Epidemiology Unit (JA), Karolinska Institutet, Stockholm, Sweden; Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark (HH, KR, MM); Department of Epidemiology, Merck Research Laboratory, West Point, PA (TNT); Department of Clinical Immunology, Odense University Hospital, Odense, Denmark (KT); Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden (AS)
Correspondence to: Gustaf Edgren, PhD, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Box 281, SE-171 77, Stockholm, Sweden (e-mail: gustaf.edgren{at}ki.se).
Background: Long-term deleterious effects of repeated blood donations may be masked by the donors’ healthy lifestyle. To investigate possible effects of blood donation and iron loss through blood donation on cancer incidence while minimizing "healthy donor effects," we made dose–response comparisons within a cohort of Swedish and Danish blood donors.
Methods: We used a nested case–control study design, in which case patients were defined as all donors who were diagnosed with a malignancy between their first recorded blood donation and study termination (n = 10866). Control subjects (n = 107140) were individually matched on sex, age, and county of residence. Using conditional logistic regression, we estimated relative risks of cancer according to number of blood donations made or estimated iron loss 3–12 years before a case patient was diagnosed with cancer. All statistical tests were two-sided.
Results: No clear association was observed between number of donations and risk of cancer overall. However, between the lowest (
median, <0.75 g) and highest (>90th percentile, >2.7 g) categories of estimated iron loss, there was a trend (Ptrend < .001) of decreasing risk for cancers of the liver, lung, colon, stomach, and esophagus, which are thought to be promoted by iron overload (combined odds ratio [OR] = 0.70, 95% confidence interval [CI] = 0.58 to 0.84), but only among men and only with a latency of 3–7 years. The risk of non-Hodgkin lymphoma was higher among frequent plasma donors (>25 vs 0 donations, OR = 2.14, 95% CI = 1.22 to 3.74).
Conclusions: Repeated blood donation was not associated with increased or decreased risk of cancer overall. The lack of consistency across latency periods casts doubt on an apparent association between reduced cancer risk and iron loss in men. The positive association between frequent plasma donation and risk of non-Hodgkin lymphoma deserves further exploration.
| CONTEXT AND CAVEATS Prior knowledge Low rates of cancer incidence and mortality among blood donors suggest that frequent blood donation does not have long-term health risks. Study design Nested case–control study within a cohort of blood donors in Denmark and Sweden. Contributions No association between number of blood or plasma donations and overall risk of cancer was observed. A dose-dependent decreasing risk of cancers of the liver, lung, colon, stomach, and esophagus—which are suggested to be promoted by iron overload—was observed among men who donated blood 3–7 years earlier. An increased risk of non-Hodgkin lymphoma was observed among frequent plasma donors. Implications Risk of overall cancer is not associated with repeated blood donation. Limitations Factors that do or may influence cancer risk, such as smoking, alcohol consumption, diet, physical activity, anthropometric measurement, and occupational exposure to carcinogens were not available in the analysis.
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Manuscript received October 8, 2007; revised January 29, 2008; accepted February 29, 2008.
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