Key points Does short-term exposure to ambient air pollution increase the risk of psoriasis flares? Findings In this case-crossover and cross-sectional study involving 957 patients affected by chronic plaque psoriasis with 4398 follow-up visits, air pollutant concentrations were significantly higher in the period before psoriasis flare compared to the control visit . Meaning These findings support that air pollution may be a trigger for psoriasis flares. |
Importance
Psoriasis is a chronic inflammatory disease with a course of relapses and remissions. Selected environmental factors, such as infections, stressful life events, or medications, can trigger disease outbreaks. It is still unknown whether air pollution could trigger psoriasis flares.
Aim
To investigate whether short-term exposure to ambient air pollution is associated with psoriasis flares.
Design, environment and participants
This observational study with case-crossover and cross-sectional design retrospectively analyzed longitudinal data from September 2013 to January 2020 of patients with chronic plaque psoriasis who consecutively attended the outpatient dermatological clinic of the University Hospital of Verona.
For case-crossover analysis, patients were included who had at least 1 disease flare, defined as an increase in the psoriasis area and severity index (PASI) of 5 or more between 2 consecutive evaluations in a time period of 3 to 5 years. 4 months.
For the cross-sectional analysis, patients who received any systemic treatment for 6 or more months, with consecutive PASI evaluation of grade 2 or higher, were included.
Main results and measures
We compared the mean and cumulative concentrations (area under the curve) of several air pollutants (carbon monoxide, nitrogen dioxide, other nitrogen oxides, benzene, coarse particulate matter [PM; 2.5-10.0 μm diameter, PM10 ] and fine PM [<2.5 μm diameter, PM2.5]) in the 60 days before psoriasis flare and control visits.
Results
A total of 957 patients with plaque psoriasis with 4398 follow-up visits were included in the study . Patients had a mean (SD) age of 61 (15) years and 602 (62.9%) were men.
More than 15,000 measurements of air pollutant concentration were retrieved from the official open source bulletin of the Italian Institute for Environmental Protection and Research (ISPRA).
Among the overall cohort, 369 (38.6%) patients with psoriasis flare were included in the case-crossover study.
We found that concentrations of all contaminants were significantly higher in the 60 days prior to the psoriasis flare (median PASI at flare 12; IQR, 9-18) compared to the control visit (median PASI 1; IQR, 1 -3, P < .001).
In cross-sectional analysis, average PM10 exposure above 20 μg/m 3 and average PM 2.5 above 15 μg/m 3 in the 60 days prior to screening were associated with an increased risk of PASI 5 or greater worsening (adjusted odds ratio [aOR], 1.55; 95% CI, 1.21-1.99; and aOR, 1.25; 95% CI, 1.0-1.57, respectively).
Sensitivity analyzes stratified by assessment quarter, with various exposure lags and adjustments for treatment type, yielded similar results.
Conclusions and relevance
The findings of this cross-sectional and cross-case study suggest that air pollution may be a triggering factor for psoriasis flare.
