Causal relationship between air pollution and rheumatoid arthritis: A two-sample Mendelian randomization study

Area of Science:

• Environmental Health
• Rheumatology
• Genetic Epidemiology

Background:

• Emerging evidence suggests a link between air pollution and autoimmune diseases.
• The specific causal relationship between common air pollutants and rheumatoid arthritis (RA) remains uncertain.
• Investigating environmental factors is crucial for understanding autoimmune disease etiology.

Purpose of the Study:

• To determine the potential causal effect of major air pollutants on rheumatoid arthritis (RA) risk.
• To utilize a robust Mendelian randomization (MR) approach for assessing genetic links.
• To provide evidence for public health strategies concerning environmental exposures and RA.

Main Methods:

• A two-sample Mendelian randomization (MR) analysis was conducted.
• Genome-wide association study (GWAS) data for air pollution metrics (PM2.5, PM10, NO2, NOx) were used as exposures.
• RA outcome data from European cohorts were analyzed using inverse variance weighting and sensitivity analyses.

Main Results:

• No significant causal association was found between PM2.5, PM10, nitrogen dioxide, or nitrogen oxides and the risk of rheumatoid arthritis.
• Inverse variance weighting and sensitivity analyses (weighted median, MR-Egger) showed consistent null results.
• No evidence of pleiotropy or heterogeneity was detected, supporting the robustness of the findings.

Conclusions:

• This study provides the first MR evidence suggesting that genetically predicted air pollution exposure does not causally influence rheumatoid arthritis risk.
• The findings indicate that common air pollutants may not be direct causal triggers for RA.
• Further research is needed to explore other potential environmental contributors to autoimmune diseases.