Occupational Exposures and Smoking in Eosinophilic Granulomatosis With Polyangiitis: A Case-Control Study

Our plain-English summary of Occupational Exposures and Smoking in Eosinophilic Granulomatosis With Polyangiitis: A Case-Control Study, by F. Maritati, F. Peyronel, P. Fenaroli, et al (Arthritis & Rheumatology, 2021).

The study

• Authors: F. Maritati, F. Peyronel, P. Fenaroli, F. Pegoraro, V. Lastrucci, G.D. Benigno, A. Palmisano, G.M. Rossi, M.L. Urban, F. Alberici, P. Fraticelli, G. Emmi, M. Corradi, A. Vaglio
• Journal: Arthritis & Rheumatology
• Published: 2021;73(9):1694-1702
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Environmental agents and occupational exposures may confer susceptibility to EGPA, but data are scarce. This study was undertaken to investigate the association between occupational exposures (e.g., silica, farming, asbestos, and organic solvents) and other environmental agents (e.g., smoking) and the risk of EGPA.

Methods: Patients with newly diagnosed EGPA (n = 111) and general population controls (n = 333) who were matched for age, sex, and geographic area of origin were recruited at a national referral center for EGPA. Exposures were assessed using a dedicated questionnaire administered by a specialist in occupational medicine, under blinded conditions. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

Results: Exposures to silica (OR 2.79 [95% CI 1.55-5.01], P = 0.001), organic solvents (OR 3.19 [95% CI 1.91-5.34], P < 0.001), and farming (OR 2.71 [95% CI 1.71-4.29], P < 0.001) were associated with an increased risk of EGPA. Co-exposure to silica and farming yielded an OR of 9.12 (95% CI 3.06-27.19, P < 0.001), suggesting a multiplicative effect between these 2 exposures. Smoking (current and former smokers combined) was significantly less frequent among patients with EGPA compared to controls (OR 0.49 [95% CI 0.29-0.70], P < 0.001). The pack-year index was also lower among patients with EGPA (OR 0.96 [95% CI 0.94-0.98], P < 0.001). The association of silica and farming was primarily aligned with ANCA-positive EGPA, while the association of smoking status and organic solvents was primarily aligned with ANCA-negative EGPA.

Conclusion: The environment can influence susceptibility to EGPA. Exposure to silica, farming, or organic solvents is associated with an increased risk of EGPA, while smoking is associated with a lower risk. These exposures seem to have distinct effects on different EGPA subsets.

© 2021, American College of Rheumatology.

In plain English

This case-control study at Parma University Hospital, Italy, compared 111 adults newly diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA), a rare disease involving blood vessel inflammation, with 333 matched controls. A blinded occupational medicine specialist asked about smoking and work exposures, including silica, asbestos, farming and organic solvents. In crude comparisons, patients were more often exposed to silica (odds ratio 2.79, 95% confidence interval 1.55 to 5.01), organic solvents (3.19, 1.91 to 5.34) and farming (2.71, 1.71 to 4.29). In the multivariable analysis these three remained associated, with lower odds ratios: silica 2.26 (1.10 to 4.62), solvents 2.20 (1.14 to 4.25) and farming 2.10 (1.19 to 3.73). Asbestos was not among the independent factors. Fewer patients were current or former smokers (34% versus 54%). Documented work exposure to asbestos was not associated with EGPA (odds ratio 0.94, 0.26 to 3.40). Possible or probable exposure showed what the authors called a weak association (2.38, 1.22 to 4.63). The authors concluded that solvents, silica and farming are associated with higher EGPA risk, and smoking with lower risk. They noted limits from questionnaire-based exposure assessment and small subgroups.

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-control study, with each patient matched to three controls from the general population; exposures assessed by a questionnaire given by a blinded occupational medicine specialist
• Who was studied: 111 newly diagnosed adult EGPA patients and 333 controls matched for age, sex and geographic origin (North vs. Centre-South of Italy). Patients were seen at the Vasculitis Clinic of Parma University Hospital, Italy, between December 2010 and October 2018. Controls were relatives or friends of patients coming to the hospital for kidney transplantation.
• Exposure: Cigarette smoking and occupational exposure to silica, asbestos, farming, organic solvents, metals, other industrial chemicals, pesticides and textile fibres. Occupational asbestos exposure was classed as documented, or possible/probable. Only occupational asbestos exposure was analysed.
• Main results:
  • Asbestos: documented occupational exposure was not associated with EGPA (OR 0.94, 95% CI 0.26-3.40, p=0.919). Possible/probable occupational exposure showed a statistically significant but, in the authors' words, weak association (OR 2.38, 95% CI 1.22-4.63, p=0.011).
  • Silica exposure was associated with EGPA in the univariable (crude) analysis (OR 2.79, 95% CI 1.55-5.01, p=0.001)
  • Organic solvent exposure was associated with EGPA in the univariable (crude) analysis (OR 3.19, 95% CI 1.91-5.34, p<0.001)
  • Farming was associated with EGPA in the univariable (crude) analysis (OR 2.71, 95% CI 1.71-4.29, p<0.001). Pesticide exposure showed no significant association.
  • Current and former smokers combined made up 34% of patients versus 54% of controls (OR 0.49, 95% CI 0.29-0.70, p<0.001)
  • In the multivariable analysis, silica (OR 2.26, 95% CI 1.10-4.62), organic solvents (OR 2.20, 95% CI 1.14-4.25) and farming (OR 2.10, 95% CI 1.19-3.73) were independently associated with higher EGPA risk, and smoking with lower risk (OR 0.39, 95% CI 0.22-0.69)
  • Combined exposure to silica and farming, compared with neither, had an OR of 9.12 (95% CI 3.06-27.19)
  • Smoking and organic solvents were more strongly associated with MPO ANCA-negative EGPA. Silica and farming were more strongly associated with MPO ANCA-positive EGPA.
• The authors' conclusion: The authors concluded that exposure to organic solvents, silica and farming is associated with an increased risk of EGPA, and smoking with a lower risk. They also concluded that these exposures seem to have distinct effects on EGPA subsets.
• Limitations the authors state:
  • Exposures were assessed by questionnaire, and the patient subgroups were small
  • Most subgroup analyses by ANCA status and disease features were underpowered
  • The study was not designed to compare exposures between ANCA-positive and ANCA-negative patients
  • Respiratory symptoms before diagnosis may have influenced patients' smoking habits
  • The study could not distinguish between different types of farming exposure

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Eosinophilic, Case-Control Study, Odds Ratio, confidence interval.

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