Association between Air Quality Index and the risk of rosacea: A nationwide population-based cohort study

Background: Air pollution is associated with several inflammatory skin disorders. However, the association between air quality and rosacea remains unclear. Objectives: To investigate the association between the Air Quality Index (AQI) and incidence of rosacea. Methods: In total, 21 709 479 participants without rosacea before 2008 were recruited from the Taiwan National Health Insurance Research Database. The long-term average AQI value for each participant was acquired from the Taiwan Air Quality Monitoring System Network and calculated from 1 January 2008 until the diagnosis of rosacea, withdrawal from the National Health Insurance programme, or 31 December 2018. Results: We observed a significant association between AQI and the incidence of rosacea, with each unit elevation in the AQI increasing the risk of rosacea by 5%. We then categorized participants equally into four groups by quantiles (Q) of AQI values, with mean AQI values of: Q1, 69.0 (SD 6.4); Q2, 79.0 (SD 2.3); Q3, 89.9 (SD 3.6); and Q4, 103.9 (SD 6.8). Compared with the Q1 group, the Q2, Q3 and Q4 cohorts exhibited 1.82-fold, 4.48-fold and 7.22-fold increased risk of rosacea, respectively. Additionally, exposure to particulate matter (PM)_2.5 (airborne particulate matter with a diameter ≤ 2.5 μm), sulfur dioxide (SO₂) and carbon monoxide increased the risk of rosacea, whereas exposure to PM₁₀ (airborne PM with a diameter ≤ 10 μm) was associated with a lower risk. Conclusions: This study supported a significant dose-response relationship between AQI and the incidence of rosacea.