Occupational inhalant exposures associated with increased rheumatoid arthritis risk in meta-analysis

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint pain, swelling, and stiffness. Although smoking is a well-established risk factor for RA, the role of occupational inhalants in RA development is less well recognized. This study aimed to systematically review and synthesize existing evidence on the association between occupational inhalants and the risk of developing RA. METHODS: We conducted a systematic review and meta-analysis following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching MEDLINE, Embase, and Web of Science from database inception to November 20, 2024. Eligible studies were cross-sectional, were case-control and cohort designs, were population-based, reported original data on occupational inhalant exposures and RA, measured exposures, included a comparison group, and used reliable RA ascertainment methods. Studies relying solely on self-reported RA or focusing on treatment, prognosis, sick leave, or death were excluded. Two reviewers independently conducted literature screening, data extraction, and risk-of-bias assessment using the Newcastle-Ottawa Scale. Random-effects meta-analyses with relative risk were performed for cohort and case-control studies, and heterogeneity was assessed using the I statistic. RESULTS: In total, 31 studies met inclusion criteria, and 25 were included in meta-analyses across 10 types of occupational inhalants. Significant associations with RA risk were observed for exposure to silica, asbestos, solvents, pesticides, fertilizers, animal dust, and engine exhaust (relative risks ranging from 1.25 to 1.49). Moderate-to-high heterogeneity was observed in seven meta-analyses. CONCLUSION: Occupational inhalants are associated with increased RA risk, underscoring the importance of workplace prevention strategies and further research into biologic mechanisms.