Is Male Rheumatoid Arthritis an Occupational Disease? A Review

Our plain-English summary of Is Male Rheumatoid Arthritis an Occupational Disease? A Review, by D. Murphy, D. Hutchinson (The Open Rheumatology Journal, 2017).

The study

• Authors: D. Murphy, D. Hutchinson
• Journal: The Open Rheumatology Journal
• Published: 2017;11:88-105
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Rheumatoid arthritis (RA) is a systemic, inflammatory disease with an estimated global prevalence of 0.3-1.0%. An unexplained association exists between low formal education and the development of RA independent of smoking. It is established that RA is initiated in the lungs and that various occupations associated with dust, fume and metal inhalation can increase the risk of RA development.

Objective: The objective of this review is to evaluate published clinical reports related to occupations associated with RA development. We highlight the concept of a "double-hit" phenomenon involving adsorption of toxic metals from cigarette smoke by dust residing in the lung as a result of various work exposures. We discuss the relevant pathophysiological consequences of these inhalational exposures in relation to RA associated autoantibody production.

Method: A thorough literature search was performed using available databases including Pubmed, Embase, and Cochrane database to cover all relative reports, using combinations of keywords: rheumatoid arthritis, rheumatoid factor, anti-citrullinated peptide antibody silica, dust, fumes, metals, cadmium, cigarette smoking, asbestos, mining, bronchial associated lymphoid tissue, heat shock protein 70, and adsorption.

Conclusion: We postulate that the inhalation of dust, metals and fumes is a significant trigger factor for RA development in male patients and that male RA should be considered an occupational disease. To the best of our knowledge, this is the first review of occupations as a risk factor for RA in relation to the potential underlying pathophysiology.

In plain English

This narrative review examined published studies on whether jobs involving inhaled dust, fumes and metals are linked to rheumatoid arthritis (RA) in men. The authors searched PubMed, Embase and Cochrane databases and did not pool the results. Asbestos was one of many exposures covered. In a Swedish study the authors reviewed, asbestos exposure was reported in 12 of 74 incident RA cases and 19 of 382 referents (OR 2.5, 95% CI 1.0-6.8). In another reviewed study, of people exposed to asbestos-contaminated vermiculite in Montana, USA, those over 65 had an OR of 3.23 (95% CI 1.31-7.96). No significant increase was seen in those under 65. The authors also described other studies in which silica and other dusts were linked to RA, mainly in smokers. They proposed that inhaled dust soaks up metals such as cadmium from cigarette smoke. The authors suggested that male RA should be considered an occupational disease. They noted that most of the evidence came from Swedish studies and that workers are often exposed to several agents.

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: Narrative literature review; no pooled analysis or systematic review was done
• Who was studied: Published reports on occupation and RA risk, mainly in men, found by searching PubMed, Embase and Cochrane databases
• Exposure: Inhaled occupational exposures including silica, other inorganic dusts, asbestos (including asbestos-contaminated vermiculite), metal fumes, mineral oils, farm chemicals, and their combination with cigarette smoking
• Main results:
  • In a reviewed Swedish study (Olsson et al. 2004), asbestos exposure was reported in 12 of 74 incident RA cases and 19 of 382 referents, with an odds ratio of 2.5 (95% CI 1.0-6.8) in multivariate analysis of lifelong occupational exposures
  • In a reviewed case-control study of community residents and workers exposed to asbestos-contaminated vermiculite in Montana, USA, those aged over 65 had an odds ratio for RA of 3.23 (95% CI 1.31-7.96)
  • In the same Montana study, no significant increased RA risk was seen in those aged under 65
  • In a reviewed Swedish study (Stolt et al. 2010), ACPA-positive RA risk compared with unexposed never smokers was OR 7.36 (95% CI 3.31-16.38) for silica exposure plus current smoking. It was OR 14.9 (95% CI 5.32-37.84) for silica plus more than 20 pack-years. For silica alone it was OR 1.15 (95% CI 0.42-3.15)
  • In a reviewed study of Swedish construction workers (Blanc et al. 2015), ever smokers exposed to silica had an RA relative risk of 1.36 (95% CI 1.11-1.68). Ever smokers exposed to other inorganic dust had a relative risk of 1.42 (95% CI 1.17-1.73). No increased risk was seen in dust-exposed never smokers
• The authors' conclusion: The authors suggested that RA should be considered an occupational disease resulting from workplace dust and fume inhalation. They proposed heavy-metal adsorption onto inhaled dust particles as a hypothesis to explain the interaction with smoking, and said further work is needed.
• Limitations the authors state:
  • Differences between the studies' populations, comparison groups and outcome measures prevented pooled analysis or systematic review
  • Workers are often exposed to multiple agents over their working lives, which may confound the studies even when they correct for smoking
  • The evidence is dominated by Swedish studies, which may not apply to other populations
  • Hospitalisation-based data (Li et al.) miss RA cases that did not need hospital treatment

Topics

Medical terms in this study, explained in our Lexicon: Occupational Disease.

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• Silicon, a Possible Link between Environmental Exposure and Autoimmune Diseases: The Case of Rheumatoid Arthritis — C.A. Speck-Hernandez, G. Montoya-Ortiz (2012)
• Occupations and exposures in the work environment as determinants for rheumatoid arthritis — A.R. Olsson, T. Skogh, et al. (2004)
• Occupational exposures and risk of esophageal and gastric cardia cancers among male Swedish construction workers — C. Jansson, A.L. Johansson, et al. (2005)
• High prevalence of occupational exposure to solvents or silica in male systemic sclerosis patients: a Belgian cohort analysis — E. De Decker, M. Vanthuyne, et al. (2018)
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