title: Allergic conditions and risk of hematological malignancies in adults: a cohort study.
abstract: BACKGROUND
  Two contradictory hypotheses have been proposed to explain the relationship between allergic conditions and malignancies, the immune surveillance hypothesis and the antigenic stimulation hypothesis. The former advocates that allergic conditions may be protective against development of cancer, whereas the latter proposes an increased risk. This relationship has been studied in several case-control studies, but only in a few cohort studies.
  
  
  METHODS
  The association between allergic conditions and risk of developing leukemia, Hodgkin's disease, non-Hodgkin's lymphoma and myeloma was investigated in a cohort of 16,539 Swedish twins born 1886-1925. Prospectively collected, self-reported information about allergic conditions such as asthma, hay fever or eczema was obtained through questionnaires administered in 1967. The cohort was followed 1969-99 and cancer incidence was ascertained from the Swedish Cancer Registry.
  
  
  RESULTS
  Hives and asthma tended to increase the risk of leukemia (relative risk [RR] = 2.1, 95% Confidence Interval [CI] 1.0-4.5 and RR = 1.6, 95% CI 0.8-3.5, respectively). There was also an indication of an increased risk of non-Hodgkin's lymphoma associated with eczema during childhood (RR = 2.3, 95% CI 1.0-5.3).
  
  
  CONCLUSIONS
  In contrast to most previous studies, our results do not indicate a protective effect of allergic conditions on the risk of developing hematological malignancies. Rather, they suggest that allergic conditions might increase the risk of some hematological malignancies.
authors.affiliation: The Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden. Karin.Soderberg@imm.ki.se
authors.forename: Karin C
authors.initials: KC
authors.lastname: Söderberg
authors.forename: Lars
authors.initials: L
authors.lastname: Hagmar
authors.forename: Judith
authors.initials: J
authors.lastname: Schwartzbaum
authors.forename: Maria
authors.initials: M
authors.lastname: Feychting
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000150:complications / Q000453:epidemiology; D015331:Cohort Studies; D004485:Eczema / Q000150:complications / Q000453:epidemiology; D005260:Female; D019337:Hematologic Neoplasms / Q000150:complications / Q000453:epidemiology* / Q000276:immunology; D006689:Hodgkin Disease / Q000150:complications / Q000453:epidemiology; D006801:Humans; D006967:Hypersensitivity / Q000150:complications / Q000453:epidemiology* / Q000276:immunology; D007938:Leukemia / Q000150:complications / Q000453:epidemiology; D008228:Lymphoma, Non-Hodgkin / Q000150:complications / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000150:complications / Q000453:epidemiology; D016016:Proportional Hazards Models; D006255:Rhinitis, Allergic, Seasonal / Q000150:complications / Q000453:epidemiology; D012306:Risk; D012650:Self Disclosure; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology