There was a substantial and persistent reduction in asthma exacerbations across England in the 18 months after the first lockdown, a large study found, likely due to a reduction in exposure to common respiratory viruses.
The findings offered a ‘clear and compelling’ demonstration that substantial reductions in asthma exacerbations were possible through public health measures, the study authors wrote in The Lancet Regional Health – Europe.
There was now a need to identify acceptable and effective ways of reducing respiratory virus exposure in patients with asthma beyond the pandemic.
Clinical approaches to manage asthma patients should also be reconsidered, they said, including redesign of waiting rooms in different clinical settings, and the use of remote consultations to mitigate the risks of exposure to other respiratory viruses.
Previous studies had reported reductions in asthma exacerbations associated with pandemic restrictions, but most of these studies were short-term.
To address the knowledge gap, researchers undertook a retrospective cohort study using data from a national primary care database of almost 10 million patients, the Optimum Patient Care Database.
They identified 100,362 patients with at least one exacerbation episode between January 2, 2016, and September 27,2021, with a total of 298,390 exacerbation episodes.
They found the mean exacerbation rate during the first quarter of 2020 was not substantially different to the control period before the pandemic (2016-2019).
However, rates were substantially lower ( > 25%) during all remaining time intervals in 2020-2021 when compared with rates during 2016-2019, with the biggest difference (63.2%) in the first quarter of 2021.
‘These reductions have been seen in all ages, both sexes, all sub-regions of England, and during varying social restrictions,’ the study authors wrote.
As such, the findings were unlikely to be adequately explained by changes in health-seeking behaviours, disruption to healthcare service over the pandemic and improvement in air quality.
‘A reduction in exposure to common respiratory viruses due to pandemic-related, non-pharmacological, public health measures is likely the most plausible explanation,’ they wrote.
‘Further research is now required to design and develop pragmatic non-pharmacological interventions that could reduce exposure to respiratory viruses and promote improved self-management to ensure that the low rate of asthma exacerbations persists beyond the Covid-19 pandemic.’
Several previous studies had suggested that respiratory virus exposure was a major asthma exacerbation trigger, they added, while increasing numbers of studies pointed to SARS-CoV-2 as being unlikely to lead to exacerbations.
‘A plausible explanation for this are mechanistic differences between how a virus binds to cells in the respiratory tract between common respiratory viruses such as rhinoviruses and SARS-CoV-2,’ they wrote.
‘In fact, some studies have hypothesised that asthma may, instead, provide a protective effect against infection with SARS-CoV-2 since the expression of ACE2 receptors (angiotensin-converting enzyme 2) is decreased in patients with asthma due to use of inhaled corticosteroids.’