Acute asthma admissions sharply declined during lockdowns as air quality improved, study reveals

Reduced pollution levels and better air quality during the Covid-19 pandemic lockdowns strongly correlated with lower rates of acute asthma care provision, according to new research led by the University of Birmingham.

The retrospective time-series study, published in the BMJ Open, investigated the link between acute asthma hospital admissions and specific air pollutant levels in four Oxford postcodes during the national lockdowns of March to June and November to December 2020.

For adult residents, acute asthma admissions fell from 78 per 100,000 residents in 2015-19, to 46 per 100,000 residents in 2020 – a reduction of 41%.

This reduction in acute asthma care coincided with levels of air pollution falling significantly. Different pollutants dropped by 18-33% when compared to average values for the previous five-year period.

For example, nitrogen dioxide (NO₂) reduced by 26.7% from a 2015-19 average of 14.6 μg m-3 to 10.7 μg m-3 in 2020.

Fine particulate matter (PM_2.5) saw a reduction of 33.5% from 10.1 μg m-3 in 2015-19 to 6.7 μg m-3 in 2020, and PM₁₀ reduced by 18.6% from 13.2 μg m-3 in 2015-19 to 10.8 μg m-3 in 2020.

‘Large-scale measures to improve air quality have potential to protect vulnerable people living with chronic asthma in urban areas,’ the authors concluded.

Commenting on the ‘unique situation’ of temporary air quality improvement, Dr Suzanne Bartington, clinical associate professor of environmental health at the University of Birmingham and lead author of the study, said: ‘The results of air pollution levels falling may have had an impact on the number of severe asthma cases that need acute hospital care, with 41% fewer hospital stays compared to the previous five-year average.

‘Furthermore, we also identified a 4% increase in risk of asthma hospital admissions for every 1 μg m-3 increase in mean monthly NO₂, and an approximately 3% increase in risk for every 1 μg m-3 increase in mean monthly PM2.5 levels.

‘This is an important study to help us better understand how demand for NHS inpatient care may change when air quality is improved.’

The research team was supported by the University of Oxford, Oxfordshire County and City Councils and the then Oxfordshire Clinical Commissioning Group.

Commenting on the results, Councillor Nathan Ley, Oxfordshire County Council’s cabinet member for public health, inequalities and community safety, said: ‘We must now use what we have learned, thanks to this research with our partners, to improve our environment, in line with the Clean Air Strategy which we launched last year.

‘Elevated levels of NO₂, PM_2.5 and PM₁₀ contribute towards heart disease, chronic lung disease, cancers, preterm births, and many other avoidable events. The vision of Oxfordshire County Council to tackle this issue remains clear. We must continue to use all the tools at our disposal to lead the country, clean up our air and save lives.’

Earlier this week, the European Respiratory Society (ERS) warned of rising respiratory diseases, such as asthma, as well as premature death without urgent action on air quality.

This followed the ERS consensus statement on climate change and respiratory health, published in September 2023, which highlighted the damaging effects of air pollution on health and global warming.