The comorbidities of psoriasis and the effects of long-term exposure to air pollution on psoriasis: an urban population–based retrospective cohort study

Background: To date, the relationship between air pollutants and psoriasis is not well established Objective: This study aimed to evaluate the effects of long-term exposure to air pollution on psoriasis. Methods: Using the Korean National Health Insurance Service-National Health Screening Cohort (NHIS-HEALS) database, incident cases of psoriasis were calculated from 2008–2015. We collected daily air pollutants from AIRKOREA and the Air Quality Analysis and Control Center in Seoul and climatological variables from the Korean Meteorological Administration. Results: Between 2008–2015, there were 1,502 incident cases with psoriasis among an urban population of 105,800 people. Ischemic heart disease and diabetes as comorbidities were significantly more common in subjects with psoriasis compared to those without psoriasis. After adjusting for age, sex, income, comorbidities, and meteorological variables, long-term exposure to air pollutants, including particulate matter <2.5 μm in diameter (hazard ratio [HR], 1.651; for 1 μg/m 3 ), particulate matter <10 μm in diameter (HR, 1.301; for 1 μg/m 3 ), sulfur dioxide (HR, 4.109; for 1 part per billion [ppb]), nitrogen dioxide (HR, 1.683; for 1 ppb), and carbon monoxide (HR, 1.330; for 1 ppb), were significantly associated with increased risk for developing psoriasis. Limitations The NHIS-HEALS database lacks detailed information on individual subjects. Conclusions: This study suggests that exposure to PM 2.5 , PM 10 , SO 2 , NO 2 , and CO independently increases the risk of developing psoriasis. Further studies are needed to investigate the mechanisms involved in the role of air pollutants in psoriasis onset.