Long-term exposure to outdoor air pollution and the risk of development of rheumatoid arthritis: A systematic review and meta-analysis

Abstract

Objectives: Air pollution ranks high among risk factors for the global burden of disease. The associations of air pollution and rheumatoid arthritis (RA) are controversial. This systematic review and meta-analyses has analyzed the association between outdoor air pollution and the development of RA.

Methods: PubMed, Embase and Web of science (last search, May 21, 2019) were searched. A meta-analysis was performed with a random-effects model, and summarized syntheses effects were expressed as relative risks (RRs).

Results: Eight studies were identified from among 1296 articles. The pooled RR for the association between ozone (O₃) exposure and RA was 1.16 (95% CI: 1.15, 1.18). The pooled RR for the association of RA risk with proximity to traffic road was 1.34 (95% CI: 1.11, 1.62) for residence ≤ 50 m from a traffic road compared with residence more far away. In contrast, there was an inverse effect between PM_2.5 exposure and incident RA, and similar result of PM₁₀ was found by subgroup analysis in seropositive RA. In addition, there was no clear evidence between exposing to PM₁₀, CO, NO₂ and NO₂ (tenth year prior) and RA risk.

Conclusion: Existing evidence indicated significant associations between some markers (ozone, proximity to traffic road and PM_2.5) of air pollution and RA. For generalizability of evidence, that research should be extended to developing countries where air pollution (including indoor) is high may provide more complete insight into risk factors for RA.

Keywords: Air pollution; Ozone; Rheumatoid arthritis; Traffic.