title: Associations of cigarette smoking with rheumatoid arthritis in African Americans.
abstract: OBJECTIVE
  To examine the associations of cigarette smoking with rheumatoid arthritis (RA) in African Americans, and to determine whether this association is impacted by the HLA-DRB1 shared epitope (SE).
  
  
  METHODS
  Smoking status, cumulative smoking exposure, and SE status were determined in African American patients with RA and African American healthy controls. Associations of smoking with RA were examined using age- and sex-adjusted logistic regression analyses. Additive and multiplicative SE-smoking interactions were examined.
  
  
  RESULTS
  After adjustment for age and sex, ever smoking (odds ratio [OR] 1.45, 95% confidence interval [95% CI] 1.07, 1.97) and current smoking (OR 1.56, 95% CI 1.07, 2.26), relative to never smoking, were more common in African American patients with RA (n = 605) than in controls (n = 255). The association of smoking with RA was limited to those with a cumulative exposure exceeding 10 pack-years, associations that were evident both in autoantibody-positive and in autoantibody-negative disease. There was evidence of a significant additive interaction between SE status and heavy smoking (≥10 pack-years) in relation to RA risk (attributable proportion [AP] due to interaction 0.58, P = 0.007), with similar results for the additive interaction between SE status and ever smoking (AP 0.47, P = 0.006). There was no evidence of multiplicative interactions.
  
  
  CONCLUSIONS
  Among African Americans, cigarette smoking is associated not only with the risk of autoantibody-positive RA but also with the risk of autoantibody-negative disease. The risk of RA attributable to smoking is limited to African Americans with more than 10 pack-years of exposure and is more pronounced among individuals positive for the HLA-DRB1 SE.
authors: University of Nebraska Medical Center and Omaha Veterans Affairs Medical Center, Omaha, USA. tmikuls@unmc.edu
authors: Ted R
authors: TR
authors: Mikuls
authors: Harlan
authors: H
authors: Sayles
authors: Fang
authors: F
authors: Yu
authors: Tricia
authors: T
authors: Levan
authors: Karen A
authors: KA
authors: Gould
authors: Geoffrey M
authors: GM
authors: Thiele
authors: Doyt L
authors: DL
authors: Conn
authors: Beth L
authors: BL
authors: Jonas
authors: Leigh F
authors: LF
authors: Callahan
authors: Edwin
authors: E
authors: Smith
authors: Richard
authors: R
authors: Brasington
authors: Larry W
authors: LW
authors: Moreland
authors: Richard J
authors: RJ
authors: Reynolds
authors: S Louis
authors: SL
authors: Bridges
mesh_terms: D000328:Adult; D001741:Black or African American / Q000235:genetics; D000368:Aged; D000483:Alleles; D001172:Arthritis, Rheumatoid / Q000453:epidemiology* / Q000235:genetics / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood; D016022:Case-Control Studies; D000939:Epitopes / Q000235:genetics; D005260:Female; D006684:HLA-DR Antigens / Q000097:blood / Q000235:genetics; D059811:HLA-DRB1 Chains; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains