Association of air quality index (AQI) with incidence of atopic dermatitis in Taiwan: A nationwide population-based cohort study

Background Air pollutants may aggravate atopic dermatitis (AD). However, the association between Air Quality Index (AQI) and incidence of AD remains unknown. Objective To investigate association between AQI and incidence of AD, using the nationwide cohort in the Taiwan National Health Insurance Research Database (NHIRD). Methods We included 21,278,938 participants from the NHIRD not diagnosed with AD before 2008. Long-term average AQI value, obtained from the Taiwan Air Quality Monitoring System Network, before AD diagnosis was calculated and linked for each participant. Results 199,205 incident cases of AD were identified from 2008-2018. Participants were classified into four quantiles (Q) by AQI value. With the lowest quantile, Q1, as reference, the AD risk increased significantly in the Q2 group (adjusted hazard ratio [aHR]: 1.29, 95% confidence interval [CI]: 1.04-1.65), Q3 group (aHR: 4.71, 95% CI: 3.78-6.04), and was highest in the Q4 group (aHR: 13.20, 95% CI: 10.86-16.60). As AQI treated as a continuous variable, an increase of one unit of AQI value added 7% of AD risk (aHR, 1.07, 95% CI: 1.07-1.08). Limitations The NHIRD lacks detailed information on individual subjects. Conclusions The results demonstrated a significant positive association between AQI and incidence of AD with a clear dose-response relationship.