title: Blood transfusion, smoking, and obesity as risk factors for the development of rheumatoid arthritis: results from a primary care-based incident case-control study in Norfolk, England.
abstract: OBJECTIVE
  To examine a range of demographic, social, and clinical risk factors for the development of rheumatoid arthritis (RA).
  
  
  METHODS
  Population-based case-control study in Norfolk, England, involving adult patients, ages 18-70, with an inflammatory polyarthritis of <12 months' duration who were recruited from the Norfolk Arthritis Register. Controls, matched for sex and date of birth, were selected from the primary care register of the Norwich Health Authority. Both cases and controls completed identical self-administered questionnaires. Matched analysis of the 165 case-control sets was conducted for the whole group and for the subset in which the cases satisfied the 1987 American College of Rheumatology criteria for RA.
  
  
  RESULTS
  The controls were of higher socioeconomic status than the cases. This was probably due to response bias. Having a body mass index > or =30 was associated with an adjusted odds ratio (OR) of 3.74 for developing RA (95% confidence interval [95% CI] 1.14-12.27). RA was also associated with a history of blood transfusion (OR 4.83, 95% CI 1.29-18.07). Even after correcting for social class, a history of having ever smoked was associated with a higher risk of developing RA (OR 1.66, 95% CI 0.95-3.06). There was no difference between cases and controls in previous exposure to childhood infections, certain surgical procedures, or reproductive history variables.
  
  
  CONCLUSIONS
  RA has a number of potential environmental triggers, including smoking, obesity, and blood transfusion.
authors.affiliation: Arthritis and Rheumatism Council Epidemiology Research Unit, University of Manchester, UK.
authors.forename: D P
authors.initials: DP
authors.lastname: Symmons
authors.forename: C R
authors.initials: CR
authors.lastname: Bankhead
authors.forename: B J
authors.initials: BJ
authors.lastname: Harrison
authors.forename: P
authors.initials: P
authors.lastname: Brennan
authors.forename: E M
authors.initials: EM
authors.lastname: Barrett
authors.forename: D G
authors.initials: DG
authors.lastname: Scott
authors.forename: A J
authors.initials: AJ
authors.lastname: Silman
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D007114:Immunization / Q000009:adverse effects; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000453:epidemiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D012959:Socioeconomic Factors; D065227:Transfusion Reaction