Occupations and exposures in the work environment as determinants for rheumatoid arthritis

Our plain-English summary of Occupations and exposures in the work environment as determinants for rheumatoid arthritis, by A.R. Olsson, T. Skogh, O. Axelson, et al (Occupational and Environmental Medicine, 2004).

The study

• Authors: A.R. Olsson, T. Skogh, O. Axelson, G. Wingren
• Journal: Occupational and Environmental Medicine
• Published: 2004;61(3):233-8
• Cited by: 84 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background And Aims: Several occupational categories have been associated with rheumatoid arthritis (RA); this study was conducted to further evaluate these associations.

Methods: Lifelong occupational history together with exposure experiences were collected through a postal questionnaire answered by 293 incident cases and 1346 population based referents. Occupational determinants were evaluated through stratified and multivariate analyses; pooled analyses with previously gathered data on 422 prevalent cases and 858 referents were also performed.

Results: In both materials, significantly increased logistic odds ratios (LORs) were seen for male conductors, freight and transport workers (LOR 17.8, 95% CI 1.5 to 207.8 and LOR 4.7, 95% CI 1.4 to 16.3, respectively), and farmers and farm workers (LOR 2.4, 95% CI 1.1 to 5.2, and LOR 2.2, 95% CI 1.3 to 3.5, respectively). Among women, increased LORs were seen in the separate and the pooled material for printmakers and process engravers (LOR 5.5, 95% CI 0.9 to 32.6, and LOR 3.0, 95% CI 0.9 to 10.3, respectively). Increased risks were seen in both materials for men exposed to asbestos (LOR 2.5, 95% CI 1.0 to 6.8, and LOR 1.6, 95% CI 0.8 to 3.3, respectively), and vibrations (LOR 2.0, 95% CI 0.9 to 4.4, and LOR 2.2, 95% CI 1.3 to 3.8, respectively). The risk for RA increased with increasing duration of exposure to vibrations and mineral dust, respectively.

Conclusions: There was evidence of a causal relation between exposures to vibrations and mineral dust and development of RA among men. Occupational factors seem to be aetiologically more important for men, and most occupations at risk involve multiple exposures. Several exposures associated with an increased risk for RA are frequent among farmers, and some of the occupations at risk include exposure to organic dust.

In plain English

This Swedish case-referent study used a postal questionnaire on lifelong jobs and work exposures to compare people newly diagnosed with rheumatoid arthritis (RA) with random population referents. Ten rheumatology units recruited 322 patients in 1996–98. The final study had 293 cases and 1346 referents, of whom 80% and 56% responded. Pooling with an earlier study gave 715 cases and 2204 referents. The main analyses counted only exposure at least 20 years before diagnosis or enrolment. For men reporting asbestos exposure (fiber type unspecified), the odds ratio was 2.5 (95% CI 1.0 to 6.8) in the new study and 1.6 (95% CI 0.8 to 3.3) pooled. Pooled odds ratios against never-exposed men were 2.8 (95% CI 1.3 to 6.2) for up to 10 years of exposure, 1.3 (0.4 to 4.3) for 11–20 years and 2.4 (0.5 to 11.3) for over 20 years. No asbestos trend test was reported. Among pooled men, RA odds rose with longer exposure to vibrations and to mineral dust (stone or silica dust, not asbestos; silica content unknown). The authors concluded there was evidence of a causal relation between these exposures and RA among men. They noted possible recall bias and selective non-response.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case-referent (case-control) study with prospective inclusion of incident cases, also analysed pooled with the authors' earlier case-referent study of prevalent cases
• Who was studied: Ten Swedish rheumatology units included 322 patients with recent-onset RA in 1996–98. After requirements of age 16–75 and birth in the Nordic countries, the study comprised 293 cases and 1346 referents, with four referents per case chosen at random from population registers. Of these, 80% of cases (n = 235) and 56% of referents (n = 752) responded. The pooled material had 715 cases and 2204 referents. Analyses of men used 74 incident cases and 382 referents, and 176 cases and 630 referents in the pooled material.
• Exposure: Self-reported lifelong occupations and specific work exposures from a postal questionnaire. These included asbestos (fiber type not specified), vibrations, mineral dust (stone or silica dust, excluding asbestos and man made mineral fibres), man made mineral fibres, mineral oils, organic dust and farm-related exposures. The main analyses required 20 years between exposure and year of diagnosis or enrolment, and were adjusted for age and smoking.
• Main results:
  • Men exposed to asbestos, with a 20-year latency requirement, in the incident-case study: 12 exposed cases and 19 exposed referents, LOR 2.5 (95% CI 1.0 to 6.8). In the pooled material: 24 cases and 33 referents, LOR 1.6 (95% CI 0.8 to 3.3).
  • Men in the pooled material, asbestos by duration of exposure, compared with never-exposed men and using a 20-year latency requirement: OR 2.8 (95% CI 1.3 to 6.2) for more than 0 up to 10 years and 1.3 (0.4 to 4.3) for 11–20 years. For more than 20 years the OR was 2.4 (0.5 to 11.3). No p for trend was given for asbestos.
  • Men exposed to vibrations, with a 20-year latency requirement: LOR 2.0 (95% CI 0.9 to 4.4) in the incident-case study and LOR 2.2 (95% CI 1.3 to 3.8) in the pooled material.
  • Among men in the pooled material, with a 20-year latency requirement, the odds of RA increased with duration of exposure to vibrations (p for trend less than 0.001) and to mineral dust (p for trend less than 0.05). Mineral dust excluded asbestos and man made mineral fibres, and its actual silica content was unknown.
  • Male conductors, freight and transport workers had increased odds: LOR 17.8 (95% CI 1.5 to 207.8) in the incident study and LOR 4.7 (95% CI 1.4 to 16.3) pooled. Male farmers and farm workers also had increased odds: LOR 2.4 (95% CI 1.1 to 5.2) in the incident study and LOR 2.2 (95% CI 1.3 to 3.5) pooled.
• The authors' conclusion: The authors concluded there was evidence of a causal relation between exposure to vibrations and mineral dust and the development of RA among men. They also concluded that occupational factors seem more important for men. Asbestos was not named in their conclusion.
• Limitations the authors state:
  • Cases knew they had RA, so recall bias is possible.
  • In the incident-case study, male referents with lower socioeconomic status were selectively lost, which may overestimate risks among blue collar workers.
  • In the pooled material, cases with lower socioeconomic status were selectively lost, which could underestimate risks for these occupations.
  • The actual silica content of the reported mineral dust is unknown.
  • Response rates were low, so the questionnaire was shortened and modified.

Topics

Medical terms in this study, explained in our Lexicon: Occupational History, Odds Ratio.

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