Abstract
Background: Previous studies suggested that exposure to air pollution could increase risk of asthma attacks in children. The aim of this study is to investigate the short-term effects of exposure to ambient air pollution on asthma hospital admissions in children in Beijing, a city with serious air pollution and high-quality medical care at the same time.Methods: We collected hospital admission data of asthma patients aged ≤ 18 years old from 56 hospitals from 2013 to 2016 in Beijing, China. Time-stratified case-crossover design and conditional Poisson regression were applied to explore the association between risk of asthma admission in children and the daily concentration of six air pollutants [particulate matter ≤ 2.5 μm (PM2.5), particulate matter ≤ 10 μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3)], adjusting for meteorological factors and other pollutants. Additionally, stratified analyses were performed by age, gender, and season.Results: In the single-pollutant models, higher levels of PM2.5, SO2, and NO2 were significantly associated with increased risk of hospital admission for asthma in children. The strongest effect was observed in NO2 at lag06 (RR = 1.25, 95%CI: 1.06-1.48), followed by SO2 at lag05 (RR = 1.17, 95%CI: 1.05–1.31). The robustness of effects of SO2 and NO2 were shown in two-pollutant models. Stratified analyses further indicated that pre-school children (aged ≤ 6 years) were more susceptible to SO2. The effects of SO2 were stronger in the cold season, while the effects of NO2 were stronger in the warm season. No significant sex-specific differences were observed.Conclusions: These results suggested that high levels of air pollution had an adverse effect on childhood asthma, even in a region with high-quality healthcare. Therefore, it will be significant to decrease hospital admissions for asthma in children by controlling air pollution emission and avoiding exposure to air pollution.
Highlights
Asthma is a common chronic respiratory disease without curable treatment
In order to select the best-fit model, all meteorological factors, influenza epidemic, and public holiday were adjusted one by one in the following basic model: Log[E(Yt)] = βZt + nsi(Xi, 3) + . . . . + factor(Xj) + intercept where, t is the day of observation; Yt refers to the number of hospital admissions for childhood asthma on day t; β refers to the vector of coefficients for Zt; Zt refers to the daily average level of the air pollutant on day t; nsi(Xi,3) indicates natural cubic spline with a fixed degree of freedom 3 to control for non-linearity of meteorological factors Xi; factor(Xj) indicates a classification variable to adjust for the effect of influenza epidemic and public holiday; intercept is the constant term
+factor(holiday) + intercept where, t is the day of observation; Yt refers to the number of childhood asthma admissions on day t; β refers to the vector of coefficients for Zt; Zt refers to the daily average level of air pollutant on day t; ns() indicates natural cubic spline with 3 df to control for non-linearity of daily mean temperature; Tmean is daily mean temperature on the same day in the original model; factor(influenza) indicates a classification variable to adjust for the effect of influenza epidemic; factor(holiday) indicates a classification variable to adjust for the effect of public holiday; intercept is the constant term
Summary
Asthma is a common chronic respiratory disease without curable treatment. It has a substantial burden of disease, and ∼273,000,000 people are afflicted worldwide [1]. According to the Global Burden of Disease Study, asthma approximately accounted for 2.29% of the global total DALYs among children aged 5–14 years in 2019 [4], implying that efficiently reducing childhood asthma hospital visits will bring about great public health benefits. Several environmental risk factors have been identified to be correlated with asthma exacerbation, such as viral infection, allergen exposure, cigarette smoking, and outdoor air pollution [5, 6]. Previous studies suggested that exposure to air pollution could increase risk of asthma attacks in children. The aim of this study is to investigate the short-term effects of exposure to ambient air pollution on asthma hospital admissions in children in Beijing, a city with serious air pollution and high-quality medical care at the same time
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