Air pollution has been associated with heart disease, asthma, COPD, cancer, making it a major public health problem of concern. It has also been implicated in spread of infection. Now findings of a recent study published in JAMA Dermatology suggest that increase in the level of air pollutants can increase the risk of flare up of disease in patients with psoriasis.

Researchers from University of Verona in Italy retrospectively analysed data of patients with chronic plaque psoriasis from September 2013 to January 2020 in a case-crossover and cross-sectional longitudinal study. More than half (62.9%) of the study population were men. There were 4398 follow-up visits and more than 15,000 measurements of air pollutants.

A total of 957 patients, mean age 61 years, attending the outpatient dermatologic clinic were selected to investigate if short-term exposure to environmental air pollution could trigger disease flare. Patients who had at least one disease flare were included in the case-crossover analysis. While for the cross-sectional analysis, those patients who had received any systemic treatment for ≥6 months with grade 2 or higher consecutive PASI assessment were included. For the purpose of the study, disease flare was defined as an increase in the Psoriasis Area and Severity Index (PASI) of ≥5 points from the last visit.

Various pollutants viz. carbon monoxide, nitrogen dioxide, other nitrogen oxides, benzene, coarse particulate matter (PM 2.5, PM10) and fine PM (<2.5 μm) were measured in the 60 days preceding the psoriasis flare and the control visits.

Disease flares occurred in 369 patients (38.6%) included in the case-crossover arm of the study. Analysis revealed that concentrations of all air pollutants were significantly higher in the 60 days before the disease flare in these patients. The median PASI score at the time of flare was 12 in these patients compared to the score of 1 at the control (no flare) visit.

In the cross-sectional analysis, a positive association was observed between the levels of particulate matter and disease flare. Concentration of air pollutants was significantly higher in the 60 days prior to visit for psoriasis flare vis a vis control visits independent of flares. After adjusting for weather conditions and systemic therapy, patients who were exposed to PM10 >20 μg/m3 (mean) and PM2.5 >15 μg/m3 (mean) in the 60 days before visits were more likely to have PASI scores of ≥5 indicative of worsening of disease with an adjusted odds ratios of 1.55 and 1.25 respectively.

Psoriasis is a chronic, relapsing skin disease. This observational study has demonstrated that concentrations of air pollutants were higher in the period before psoriasis flare. Although it does not show a clear dose-response relationship between exposure to air pollution and increased risk of worsening of disease, this study does show an association and suggests air pollution as a trigger for flare up of psoriasis. Hence, environmental triggers should be considered in patients experiencing flare up of their disease.

Reference

1. Bellinato F, et al. Association between short-term exposure to environmental air pollution and psoriasis flare. JAMA Dermatol. 2022 Feb 16;e216019. doi: 10.1001/jamadermatol.2021.6019.