title: Blood donation and risk of polycythemia vera.
abstract: It has been suggested that blood donors could have an increased risk of polycythemia vera (PV). However, no study has assessed whether frequent donors have a higher PV risk than less frequent donors.
  
  
  
  From the Scandinavian Donations and Transfusions (SCANDAT2) database, we established a cohort of blood donors who had donated whole blood at least once between 1980 and 2012. Within this cohort we first assessed the risk of PV, comparing the donors to the general population using standardized incidence ratios (SIRs) with corresponding 95% confidence intervals (CIs). To assess the association between frequency of blood donation and risk of PV we then conducted a case-control study nested within the cohort, where we compared prior donation activity among donors who were diagnosed with PV and matched controls. Here odds ratios (ORs) were used as measures of relative risk comparing donors with different donation frequency.
  
  
  
  Among 1.4 million donors in the cohort a total of 271 donors developed PV, yielding a SIR of 1.00 (95% CI, 0.89-1.13) compared to the general population. The nested case-control study showed no association between donation frequency and risk of PV. The OR of PV comparing donors who had made at least 33 donations in the period from 3 to 22 years before diagnosis of the case, to donors with one to eight donations in the same period was 1.01 (95% CI, 0.51-1.97).
  
  
  
  We find no evidence of excess risk of PV among blood donors or of an association between donation frequency and PV risk.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Hematology Center, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Gustaf
authors.initials: G
authors.lastname: Edgren
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Nyrén
authors.affiliation: Hematology Center, Karolinska University Hospital, Stockholm, Sweden.|Division of Hematology, Department of Medicine, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Hultcrantz
authors.affiliation: Department of Clinical Immunology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Kaspar Rene
authors.initials: KR
authors.lastname: Nielsen
authors.affiliation: Department of Clinical Immunology, Naestved Hospital, Naestved, Denmark.
authors.forename: Ole B V
authors.initials: OB
authors.lastname: Pedersen
authors.affiliation: Hematology Center, Karolinska University Hospital, Stockholm, Sweden.|Division of Hematology, Department of Medicine, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Björkholm
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Klaus
authors.initials: K
authors.lastname: Rostgaard
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.|Department of Hematology, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hjalgrim
mesh_terms: D000368:Aged; D001782:Blood Donors; D016022:Case-Control Studies; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011087:Polycythemia Vera / Q000453:epidemiology / Q000209:etiology*; D012306:Risk; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology