title: Silica exposure among male current smokers is associated with a high risk of developing ACPA-positive rheumatoid arthritis.
abstract: OBJECTIVE
  To study the association between silica exposure, separately as well as combined with smoking, and the risk of developing rheumatoid arthritis (RA) with or without the presence of antibodies against citrullinated peptide antigens (ACPA).
  
  
  METHODS
  This Swedish population based case-control study analysed 577 incident RA cases and 659 randomly selected controls, all men aged 18-70 years, included during May 1996 to May 2006. Self-reported silica exposure, defined as exposure to stone dust, rock drilling or stone crushing and cigarette smoking was registered. ACPA status among cases was analysed.
  
  
  RESULTS
  Silica-exposed subjects were found to have a moderately increased risk of ACPA-positive RA (odds ratio (OR) adjusted for age and residency=1.67 (95% CI 1.13 to 2.48), but not of ACPA-negative RA (OR=0.98 (95% CI 0.57 to 1.66)), compared with subjects unexposed to silica.
  
  
  METHODS
  exposed to rock drilling were found to have a somewhat more markedly increased risk of ACPA-positive RA (OR=2.34 (95% CI 1.17 to 4.68)). A high risk of developing ACPA-positive RA was observed among silica-exposed current smokers (OR=7.36 (95% CI 3.31 to 16.38)), exceeding the risk expected from the separate effects of silica exposure and current smoking, indicating an interaction between these exposures (attributable proportion due to interaction=0.60 (95% CI 0.26 to 0.95)).
  
  
  CONCLUSIONS
  Silica exposure combined with smoking among men is associated with an increased risk of developing ACPA-positive RA. These results suggest that different inhalation exposures may interact in the aetiology of ACPA-positive RA.
authors: Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden. patrikstolt@swipnet.se
authors: Patrik
authors: P
authors: Stolt
authors: Abqariyah
authors: A
authors: Yahya
authors: Camilla
authors: C
authors: Bengtsson
authors: Henrik
authors: H
authors: Källberg
authors: Johan
authors: J
authors: Rönnelid
authors: Ingvar
authors: I
authors: Lundberg
authors: Lars
authors: L
authors: Klareskog
authors: Lars
authors: L
authors: Alfredsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000209:etiology* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood; D016022:Case-Control Studies; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects / Q000032:analysis; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D010456:Peptides, Cyclic / Q000276:immunology; D012822:Silicon Dioxide / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012822:Silicon Dioxide