A JAMA Dermatology study found that greater exposure to air pollutants, such as carbon monoxide and fine particulate matter, were significantly associated with later psoriasis flares.

Higher exposure to air pollutants may increase the risk of flare and more severe disease in patients with psoriasis, according to study findings published today in JAMA Dermatology.

Characterized by a relapsing-remitting course, psoriasis flares have been noted to be triggered by environmental factors, including infections, stressful life events, and drugs. Moreover, worsening of other diseases that share common inflammatory pathways to psoriasis, such as atopic dermatitis, have been associated with exposure to air pollution.

“After inhalation, pollutants can circulate in the bloodstream, exerting oxidative damage and causing inflammation…air pollutants can directly come into contact with the skin,” said the study authors. “Whether air pollution could trigger psoriasis flares is not known.”

Seeking to investigate whether short-term exposure to environmental air pollution is associated with psoriasis flares, they conducted an observational study, comprised both case-crossover and cross-sectional analyses. They retrospectively analyzed longitudinal data from September 2013 to January 2020 on patients with chronic plaque psoriasis consecutively attending the outpatient dermatologic clinic of the University Hospital of Verona.

Mean and cumulative (area under the curve [AUC]) concentrations of several air pollutants were compared in the 60 days preceding the psoriasis flare and control visits, including for carbon monoxide, nitrogen dioxide, other nitrogen oxides, benzene, coarse particulate matter (PM; 2.5-10.0 mcm in diameter, PM10) and fine PM (< 2.5 mcm in diameter, PM2.5).

Patients recruited for the case-crossover analysis had at least 1 disease flare, defined as Psoriasis Area and Severity Index (PASI) increase of 5 or greater between 2 consecutive assessments in a time frame of 3 to 4 months, whereas patients selected for the cross-sectional analysis included those who received any systemic treatment for 6 or more months, with grade 2 or higher consecutive PASI assessment.

Overall, the study included data on 957 patients with plaque psoriasis with 4398 follow-up visits (mean [SD] age, 61 [15] years; 62.9% male) and more than 15,000 measurements of air pollutant concentrations from the official, open-source bulletin of the Italian Institute for Environmental Protection and Research.

A total of 369 (38.6%) patients with psoriasis flare were included in the case-crossover study and 4072 follow-up visits from 957 patients were used for the cross-sectional analysis.

In findings of the case-crossover study, concentrations of all pollutants (as mean and AUC) were shown to be significantly higher in the 60 days before psoriasis flare (median [interquartile range] PASI, 12 [9-18]), compared with the control visit (median PASI, 1 [1-3); P < .001).

Further sensitivity analyses applying different definitions of psoriasis flare, such as 50% and 100% increases in PASI, indicated that 515 (35.8%) patients had at least a 50% increase and 452 (47.2%) had at least a 100% increase in PASI compared with the control visit, respectively.

Regarding the cross-sectional analysis, exposure to mean PM10 over 20 mcg/m3 and mean PM2.5 over 15 mcg/m3 in the 60 days before assessment were associated with a higher risk of PASI 5 or more points worsening (adjusted OR [aOR], 1.55; 95% CI, 1.21-1.99; aOR, 1.25; 95% CI, 1.0-1.57, respectively). Sensitivity analyses that stratified for trimester of evaluation, with various lag of exposure and adjusting for type of treatment, were found to yield similar results.

“Further study is needed to examine whether these findings generalize to other populations and to better understand the mechanisms by which air pollution may affect psoriasis disease activity,” the concluded researchers.

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