Joint exposure to multiple air pollutants, genetic risk, and incident psoriasis: a large-scale prospective cohort study.

Background: Air pollution and genetic risk have been found to contribute to both onset and development of psoriasis. However, the extent to which genetic susceptibility modifies the effects of air pollutants on the risk of incident psoriasis remains unknown.

Objectives: Our study aimed to assess the association between joint exposure to multiple air pollutants and the risk of psoriasis and the modification by the genetic susceptibility.

Methods: This prospective study included 451,064 participants with complete air pollution data and free of psoriasis at baseline from the UK Biobank. All participants were enrolled from 2006 to 2010 and followed up to 2022. The air pollution score (APS) was calculated to assess the joint exposure to multiple air pollutants, including particulate matter (PM) with diameters ≤ 2.5 μm (PM2.5), between 2.5 and 10 μm (PM2.5-10), and ≤ 10 μm (PM10), as well as nitrogen dioxide (NO2) and nitrogen oxides (NOx). To evaluate the genetic risk, the polygenic risk score (PRS) for psoriasis was constructed. The Cox proportional hazard models were used to assess the association of air pollution and genetic susceptibility with the risk of psoriasis. Stratified analyses were conducted based on the individual characteristics.

Results: During a median follow-up of 13.79 years, 4414 psoriasis events were recorded. The hazard ratios (HRs) [95% confidence intervals (CIs)] for psoriasis were 1.036 (0.936-1.147), 1.091 (0.987-1.206), 1.159 (1.048-1.283), and 1.163 (1.052-1.286) in higher quintile groups compared with the lowest quintile of APS (P trend <0.05). When considering genetic susceptibility, participants with high PRS and high APS had the greatest risk of incident psoriasis [HR (95% CI): 1.962 (1.630-2.362)] than those with low PRS and low APS. The HRs (95% CIs) for PM2.5-10, NOx, PM2.5 absorbance, PM2.5, NO2, and PM10 in the group with high exposure level and genetic risk were 1.831 (1.537-2.181), 1.722 (1.431-2.073), 1.698 (1.416-2.037), 1.619 (1.353-1.938), 1.504 (1.252-1.806), and 1.425 (1.192-1.704), respectively.

Conclusions: Long-term exposure to various air pollutants is positively associated with an increased risk of incident psoriasis, particularly in individuals with high genetic risk. More comprehensive measures are needed to reduce the air pollution levels for better prevention of psoriasis.