Short-Term Nitrogen Dioxide Exposure and Emergency Hospital Admissions for Asthma in Children: A Case-Crossover Analysis in England

Abstract

Weiyi Wang,1,2 John Gulliver,3 Sean Beevers,4,5 Anna Freni Sterrantino,1,6 Bethan Davies,1,2 Richard W Atkinson,3 Daniela Fecht1,2 1UK Small Area Health Statistics Unit, MRC Centre for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK; 2National Institute for Health and Care Research Health Protection Research Unit in Chemical and Radiation Threats and Hazards, School of Public Health, Imperial College London, London, UK; 3Population Health Research Institute, St George’s, University of London, London, UK; 4MRC Centre for Environment and Health, Environmental Research Group, School of Public Health, Imperial College London, London, UK; 5National Institute for Health and Care Research Health Protection Research Unit in Environmental Exposures and Health, School of Public Health, Imperial College London, London, UK; 6The Alan Turing Institute, London, UKCorrespondence: Weiyi Wang, MRC Centre for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK, Email [email protected]: There is an increasing body of evidence associating short-term ambient nitrogen dioxide (NO2) exposure with asthma-related hospital admissions in children. However, most studies have relied on temporally resolved exposure information, potentially ignoring the spatial variability of NO2. We aimed to investigate how daily NO2 estimates from a highly resolved spatio-temporal model are associated with the risk of emergency hospital admission for asthma in children in England.Methods: We conducted a time-stratified case-crossover study including 111,766 emergency hospital admissions for asthma in children (aged 0– 14 years) between 1st January 2011 and 31st December 2015 in England. Daily NO2 levels were predicted at the patients’ place of residence using spatio-temporal models by combining land use data and chemical transport model estimates. Conditional logistic regression models were used to obtain the odds ratios (OR) and confidence intervals (CI) after adjusting for temperature, relative humidity, bank holidays, and influenza rates. The effect modifications by age, sex, season, area-level income deprivation, and region were explored in stratified analyses.Results: For each 10 μg/m³ increase in NO2 exposure, we observed an 8% increase in asthma-related emergency admissions using a five-day moving NO2 average (mean lag 0– 4) (OR 1.08, 95% CI 1.06– 1.10). In the stratified analysis, we found larger effect sizes for male (OR 1.10, 95% CI 1.07– 1.12) and during the cold season (OR 1.10, 95% CI 1.08– 1.12). The effect estimates varied slightly by age group, area-level income deprivation, and region.Significance: Short-term exposure to NO2 was significantly associated with an increased risk of asthma emergency admissions among children in England. Future guidance and policies need to consider reflecting certain proven modifications, such as using season-specific countermeasures for air pollution control, to protect the at-risk population.Keywords: asthma, nitrogen dioxide, children, hospital admissions, case-crossover

Keywords

• asthma
• nitrogen dioxide
• children
• hospital admissions
• case-crossover