Short-term impact of ambient air pollution exposure on daily clinic visits for patients with urticaria in Kaohsiung, Taiwan

Abstract

The aim of this study was to investigate associations between daily visit count for patients with urticaria (DVCPU) and short-term changes in ambient air pollutant concentrations. Information of DVCPU with an ICD-9 diagnostic code 708 in out-patient clinic visits was retrieved from the medical records of Kaohsiung Veterans General Hospital from January 1, 2014, to July 31, 2018, as a dependent variable. Ambient air pollutant data were retrieved from the Taiwan Air Quality Monitoring Network database including carbon monoxide (CO), ground-level ozone (O3), particulate matter (PM)10, PM2.5, nitrogen dioxide (NO2), and nitric oxide (NO). Independent variables included one-day weighted 75th percentile values of one kind of air pollutant, meteorological factors (temperature, humidity, wind speed, and rainfall), and weekdays in the same model. Multivariable Poisson regression was used for analysis. DVCPU was significantly positively associated with an increasing level of NO2 on the 1st–3rd lag days (relative risk (RR): 1.02~1.03) and O3 on the 1st and 3rd lag days (RR = 1.002). Men were associated with CO on the visit day and 1st–5th lag days (RR: 1.65~2.06) and PM10 on the 1st (RR = 1.002) and 3rd lag days (RR = 1.003). Women were associated with CO on the 3rd–4th lag days (RR = 1.4) and O3 on the 1st (RR = 1.003) and 5th (RR = 1.004) lag days. The non-elderly (age < 65 years) was associated with O3 on the 1st (RR = 1.003) and 3rd (RR = 1.002) lag days. The elderly (age ≥ 65 years) was associated with CO on the visit day, 1st, 3rd, and 5th lag days (RR: 1.94~4.67), PM2.5, and PM10 on the visit day (RR = 1.01). Ambient air pollutants exposure was an important risk factor for patients with urticaria seeking treatment on certain days among the visit day and lag days.