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Original article
Occupational exposure to organic dusts and risk of developing rheumatoid arthritis: findings from a Swedish population-based case–control study
  1. Anna Ilar1,
  2. Per Gustavsson2,3,
  3. Pernilla Wiebert2,3 and
  4. Lars Alfredsson1,3
  1. 1Unit of Translational Epidemiology, The Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
  2. 2Unit of Occupational Medicine, The Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
  3. 3Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden
  1. Correspondence to Anna Ilar; anna.ilar{at}ki.se

Abstract

Objectives We estimated the association between occupational exposures to five different organic dusts: wood, animal, paper, textile and flour dust and the risk of developing rheumatoid arthritis (RA).

Methods This population-based case–control study analysed 12 582 incident cases and 129 335 controls. Participants were identified from national public authority and quality registers. Census data on occupations were collected 1960–2010 and we estimated the exposure to organic dust with the help of job-exposure matrices. We used logistic regression to assess the OR of seropositive or seronegative RA. Estimates were adjusted for the matching variables (sex, county, age and index year), education and occupational silica exposure.

Results Exposure to animal dust was associated with an increased risk of RA among both men and women. The OR was 1.2 (95% CI=1.1 to 1.4) for seropositive RA and 1.3 (95% CI=1.1 to 1.5) for seronegative RA among ever exposed participants compared with unexposed. The risk increased with duration of exposure for seropositive RA, and participants who had been exposed in five or more censuses had an OR of 1.6 (95% CI=1.1 to 2.2, p for trend=0.003). Exposure to textile dust also generated a significant dose–response relationship for seropositive RA (p for trend=0.014). We detected no association between exposure to wood, paper or flour dust and risk of RA.

Conclusions Overall, exposure to animal dust and textile dust was associated with an increased risk of developing RA. These observations give further support to the notion that airborne exposures are involved in the aetiology of RA.

  • epidemiology
  • rheumatoid arthritis
  • smoking

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Footnotes

  • Contributors AI had full access to all the data used for the analysis in this study and takes full responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: AI, LA and PG. Acquisition of data: AI, LA and PW. Statistical analysis: AI. Analysis and interpretation of data: all authors. Drafting of manuscript: AI. Critical revision of manuscript and final approval given: all authors.

  • Funding The present study was supported by grants from the Swedish Research Council for Health, Working Life and Welfare (grant no: 2013-0194) and AFA Insurance (grant no: 120299).

  • Competing interests LA have for the EIRA study been supported by research grants from the Swedish Medical Research Council; the Swedish Council for Health, Working Life and Welfare; King Gustaf V:s 80-year foundation; the Swedish Rheumatism Foundation; Stockholm County Council; the insurance company AFA Insurance and the IMI-supported RTCure projects, unrelated to the submitted work. PW has received research grants from AFA Insurance, unrelated to the submitted work. PG has received research grants from the Swedish Research Council for Health, Working Life and Welfare, unrelated to the submitted work. LA received grants from the Swedish Research Council for Health, Working Life and Welfare (grant no: 2013-0194) and AFA Insurance (grant number 120299) to support the present study.

  • Patient consent for publication Not required.

  • Ethical approval Ethical approval for the linkage between the National Patient Register, the Swedish Rheumatology Register, the Swedish Prescribed Drug Register, the national population register and the EIRA study was granted by the regional Stockholm ethics committee (Dnr 2009/2005-31/3 and Dnr 2010/939-32). Ethical approval for the EIRA study was granted by the ethics committee at Karolinska Institutet and the Regional Stockholm ethics committee (Dnr 96-174 and Dnr 2006/476-31/4).

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

  • Data availability statement No data are available.

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