Understanding the Relationship Between Short-term Air Pollution Exposure and Asthma Exacerbations: East London Cohort Study

BackgroundMultiple interacting factors including demographic and lifestyle [1], genetic predisposition [2,3], and environmental factors [4,5], influence asthma prevalence and severity.In primary care, air pollution is increasingly recognised as an important environmental factor influencing patterns of morbidity and mortality.Research indicates that there is a risk of increased adverse respiratory symptoms in adults and children even in areas with relatively low levels of pollution [6][7][8].Numerous studies have explored the link between air pollution with asthma mortality and hospital admissions.Fewer have explored other significant morbidities such as asthma exacerbation managed in the community.Here we investigated this relationship in adults (18-80 years) living in London between March 2019 and February 2023, a period of considerable change in traffic related pollution emissions due to combined action of multiple policies, including London's Ultra Low Emission Zone, and the impact of traffic restrictions during the COVID-19 lockdown periods. MethodsConsidering the substantial health and economic impacts of less severe exacerbations treated in the primary care setting, our study aimed to investigate the relationship between these exacerbations and short-term air pollution exposure (NO2, PM2.5 and PM10, and O3).We selected a cohort of asthma-registered adults in East London (71,620 out of population of 5,791,542 individuals registered to GPs) and extracted their medical records over four years.using oral corticosteroid courses (OCS) as a marker of asthma exacerbations.To investigate the effects of the COVID-19 pandemic, we defined a time varying variable with three levels: pre-COVID (1 st March 2019 -28 th Feb. 2020), peri-COVID (1 st March 2020 -28 th Feb. 2022), and post-COVID (1 st March 2022 -28 th Feb. 2023).We also investigated seasonal and day-of-week effects. ResultsOur findings indicated that for every IQR increase in preceding weeks pollutant exposure the risk of OCS prescription increased by 5%, 2% and 2%, for ambient NO2, PM10 and PM2.5 respectively.Estimated IRRs for seasonal effects of spring, summer and winter on daily OCS prescription were similar in the four single-pollutant models for NO2, PM10, PM2.5 and O3; during summer the risk of asthma exacerbation decreased (for example IRR, 0.96; 95% CI, 0.94-0.097 in NO2 model) compared to the spring, while it increased during winter (IRR, 1.28; 95% CI, 1.25-1.31 in NO2 model).Risks for OCS prescription were 2% lower during the COVID-19 period, and 28% higher in the post-COVID-19 period, compared to the pre-COVID-19 period. ConclusionIn conclusion, our study sheds light on the intricate relationship between short-term air pollution exposure and mild asthma exacerbations treated in primary care settings.We found notable associations between increased levels of NO2, PM10, and PM2.5 and heightened risks of asthma exacerbations.These findings underscore the urgency of implementing targeted interventions and policies to reduce air pollution, particularly those derived from traffic.