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Amount of smoking, duration of smoking cessation and their interaction with silica exposure in the risk of rheumatoid arthritis among males: results from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study
  1. Pingling Zeng1,
  2. Zuomei Chen1,
  3. Lars Klareskog2,
  4. Lars Alfredsson1,3,
  5. Camilla Bengtsson1,
  6. Xia Jiang1
  1. 1 Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden
  2. 2 Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden
  3. 3 Center for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden
  1. Correspondence to Pingling Zeng, Institute of Environmental Medicine, Karolinska Institute, 171 77, Stockholm, Sweden; pingling.zeng{at}

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Cigarette smoking is a well-established environmental risk factor for rheumatoid arthritis (RA),1–3 particularly anticitrullinated protein antibody (ACPA)-positive RA.2 We previously observed an association between silica exposure and increased risk of seropositive RA.4 5 While the additive interaction between silica exposure and smoking has been demonstrated,5 considerably less is known regarding the dose of smoking required to elicit this effect. In this study, we extend our previous findings on smoking and silica exposure by investigating the additive interaction between silica exposure and dose of smoking as well as between silica exposure and duration of smoking cessation, with regard to the risk of developing ACPA-positive RA.

Our study is based on the Swedish Epidemiological Investigation of Rheumatoid Arthritis project,3 an ongoing population-based study comprising incident cases (American College of Rheumatology 1987 or 20106 7 criteria) and controls aged ≥18 years living in Sweden between 1996 and 2014. Information …

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  • Contributors All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. PZ and XJ have full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

  • Funding This work was supported by grants from the Swedish Research Council for Health, Working Life and Welfare; the Swedish Foundation for Strategic Research; the COMBINE public–private research programme; Swedish Research Council; and EU-IMI BTCure.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Ethics committee of the Karolinska Institutet.

  • Provenance and peer review Not commissioned; externally peer reviewed.