Respiratory medication sales and urban air pollution in Brussels (2005 to 2011)

Background: We investigated the associations between daily sales of respiratory medication and air pollutants for various age groups in the Brussels-Capital Region (about one million inhabitants). Methods: Daily average concentrations of PM10, and NO2 at a resolution 4x4km were derived by interpolation from monitoring stations. These data was combined with reimbursement data of prescribed asthma and COPD medication from the Belgian social security for years 2005 to 2011. In this time-series study, we used over-dispersed Poisson Generalized Linear Models adjusted for daily minimum temperature, relative humidity, day of the week and influenza. We obtained up-to-three-week cumulative risk ratios (RR) for interquartile range (IQR) of exposure and their 95% confidence intervals (CI) for all ages and seven age groups. Findings: Median daily concentrations of PM10 and NO2 were 25µg/m3 (IQR=17·1) and 38µg/m3 (IQR=20·5), respectively. PM10 was associated with daily medication sales among individuals aged 13 to 64 years. For NO2, significant associations were observed among all age groups except >84 years old. The strongest RR were for NO2, among adolescents, including three weeks lags (RR=1.187 95%CI: 1.097-1.285). Interpretation: Daily concentrations of PM10 and NO2 were associated with increased sales of asthma and COPD medication in Brussels. For NO2, these associations were already established among pre-school age children and evident up to the young elderly (<85 years old). Our results further support the harmfulness of air pollution in the general population for respiratory diseases.