Impact of COVID-19 lockdown on emergency asthma admissions and deaths: national interrupted time series analyses for Scotland and Wales
Thorax Published online 29 March, 2021 | https://thorax.bmj.com/content/76/9/867
Impact of COVID-19 national lockdown on asthma exacerbations: interrupted time-series analysis of English primary care data
Thorax Published online 29 March, 2021 | https://thorax.bmj.com/content/76/9/860
Digest author(s): Emer Kelly, e-Learning Director / 28 September, 2021
These two papers were published in the same edition of Thorax in September. They both address the question of the impact of COVID-19 lockdown on asthma exacerbations in large patient cohorts. In the initial stages of the pandemic, studies had suggested that those with respiratory disease, including asthma, were at increased risk of death from COVID-19. Later studies suggested that asthma was not over-represented among those hospitalised with COVID. Lockdown created other changes that could influence asthma exacerbation: air quality improved, mask wearing and improved hand hygiene decreased circulating respiratory viruses, shielding in the UK population was suggested for those with significant asthma and self-management may have been improved.
In the Scottish and Welsh cohort this is looked at through the dataset of the Public Health Scotland (PHS) and Secure Anonymised Information Linkage (SAIL) Databank in Wales. In this study the two primary outcome measures were severe asthma exacerbations: asthma related emergency hospital admission and death due to asthma. Examining deaths as an outcome was particularly important due to the concern that exacerbations may not have presented due to fear of increased risk of COVID in the hospitals and could possibly have increased death rates. The English study used the Optimum Patient Care Database (OPCRD), a primary care database and followed the cohort of patients with asthma from January 2016 to August 2020 with the outcome measure of asthma exacerbations determined for every patient for each week with an interrupted time-series study comparing the COVID-19 year with the pre-COVID-19 years (the control period).
The first study showed that emergency admissions for asthma in Scotland and Wales in 2020 were consistently lower than the 5 year averages since the beginning of the year. The average weekly admissions decreased by 36.4 (48.7%) in Scotland and 43.5 (69.9%) in Wales compared with the first 12 weeks and by 45.8% in Scotland and 43.1% in Wales when compared to the same weeks over the previous 5 year average. There was no significant effects on asthma deaths.
In the English study, comparing pre-lockdown to post-lockdown period, a statistically significant reduction in the level of almost 20 episodes for every 100 patients with asthma (-0.196 episodes per person year, p<0.001) of exacerbation rates was seen across all patients. There was no significant change in more serious exacerbations that required hospital attendances and/or admission.
There are some limitations to these studies. The Scotland and Wales study does not confirm a causal effect and the changes may be due to the many changes that the pandemic created. There is a great advantage to the large numbers in the study but case definitions of asthma admissions and deaths have not been validated and this could affect some of the accuracy of the data. The English study also had large numbers but the cohort accessed only primary care.
The strength of having these two papers published together supports the hypothesis that the set of circumstances of the pandemic brought about a reduction in asthma exacerbations. The possible reasons for this and the implications for future policy decisions will likely be discussed widely.