Original Article
Asthma
The Impact of Social Distancing in 2020 on Admission Rates for Exacerbations in Asthma: A Nationwide Cohort Study

https://doi.org/10.1016/j.jaip.2022.04.020Get rights and content

Background

Social distancing measures introduced during the coronavirus disease 2019 pandemic have reduced admission rates for various infectious and noninfectious respiratory diseases. We hypothesized that rates of asthma exacerbations would decline following the national lockdown in Denmark.

Objective

To determine weekly rates of in- and out-of-hospital asthma exacerbations before and during the social distancing intervention implemented on March 12, 2020.

Methods

All individuals older than 18 years with at least 1 outpatient hospital contact with asthma as the main diagnosis from January 1, 2013, to December 31, 2017, were included. Weekly asthma exacerbation rates from January 1, 2018, to May 22, 2020, were calculated. An interrupted time-series model with the lockdown on March 12, 2020, as the point of interruption was used.

Results

A total of 38,225 patients with asthma were identified. The interrupted time-series model showed no immediate fall in exacerbation rates during the first week after March 12, 2020. However, there was a significant decline in weekly exacerbation rates in the following 10 weeks (change in trend for exacerbations requiring hospitalization: −0.75 [95% CI, −1.39 to −0.12]; P < .02 and in all asthma exacerbations: −12.2 [95% CI, −19.1 to −5.4; P < .001), amounting to a reduction of approximately 1 and 16.5 exacerbations per year per 100 patients in the cohort, respectively.

Conclusions

The introduction of the social distancing measures in Denmark did not lead to an immediate reduction in asthma exacerbation rates; however, a gradual decline in exacerbation rates during the following 10-week period was observed.

Introduction

Asthma affects an estimated 315 million people worldwide,1 and despite currently available highly effective treatment regimes, 20% to 40% of patients experience at least 1 acute exacerbation every year.2,3 Consequently, research in pharmacological and nonpharmacological strategies to reduce the risk of acute exacerbations in asthma is much warranted.

Social distancing measures introduced during the coronavirus disease 2019 (COVID-19) pandemic have reduced admission rates for respiratory tract infections.4,5 Because viral airway infections have been associated with up to 80% of acute exacerbations in asthma,6,7 it has been hypothesized that the social distancing measures introduced during the pandemic would lead to an overall decline in asthma exacerbations.

Earlier studies have reported reduced hospital admission rates for asthma exacerbations during the period in which the social distancing measures were implemented.8,9 However, it is important to take into account that in this period, a significant reduction in health care utilization among patients with chronic diseases was observed, explained by a reduced availability of health care services due to the lockdown and possibly also due to patients’ fear of contracting the infection while leaving their houses.10,11 Therefore, when aiming to establish the effects of social distancing measures on incidences of asthma exacerbations, it is crucial to evaluate both in- and out-of-hospital exacerbations because the observed number of hospital admissions may underestimate the true number of incident asthma exacerbations.

Using data from the Danish nationwide health registers, we aimed to identify weekly incidence rates of asthma exacerbations, including in- and out-of-hospital exacerbations, and compare incidence rates during the social distancing period to the expected incidence rates based on interrupted time-series (ITS) analyses using data from the 2 previous years.

Section snippets

Study design

The study is a retrospective cohort study using data from the Danish nationwide health registers. Data analyses began June 1, 2021, after receiving access to data from the national health administrative registries.

Ethical approval

The study has been approved by the Danish Data Protection Agency (journal no. P-2020-989). In Denmark, retrospective use of registry data does not require ethical approval or patient consent.

Cohort

The cohort was defined as follows: all Danish inhabitants older than 18 years by January 1,

Cohort

Of the 38,225 patients with asthma identified (61% women, most aged 45-74 years) (Table II and Figure 2), 6562 patients (17.1%) had at least 1 exacerbation during the follow-up period from January 1, 2018, through May 22, 2020.

Exacerbations during follow-up

During the social distancing period (March 12 to May 22, 2020), a total of 948 exacerbation episodes were experienced by 900 patients (2.4% of the total cohort). Of these episodes, 71 (7%) required hospitalization. During the corresponding period the year before (March 12

Discussion

Using nationwide health registers, we found a significant gradual decline in the rate of asthma exacerbations requiring hospitalization as well as overall asthma exacerbation rates during the 10 weeks following the introduction of the social distancing measures. Because viral respiratory infections are known to cause many asthma exacerbations, this gradual decline may represent a general decline in the level of respiratory infections in society, gradually lowering infection rates.

Surprisingly,

Conclusions

We observed a moderate trend toward a reduction in asthma exacerbation rates following the national lockdown introduced on March 12, 2020, while evaluating the overall number of in- and out-of-hospital exacerbations. Although the extensive social distancing measures are clearly too comprehensive to routinely advise to patients with asthma, our results suggest that patients with asthma should be encouraged to follow basic hygiene principles whenever possible.

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  • Cited by (0)

    This study was funded by The Novo Nordisk Foundation (grant no. NNF20OC0060657).

    Conflicts of interest: C. S. Ulrik has received personal fees from AstraZeneca, GlaxoSmithKline, TEVA, Sanofi Genzyme, Boehringer-Ingelheim, Chiesi, Orion Pharma, Novartis, ALK-Abelló, Mundipharma, and Actelion outside the submitted work. The rest of the authors declare that they have no relevant conflicts of interest.

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