key: cord-1046812-ykfidmzv
authors: Wee, Liang En; Conceicao, Edwin Philip; Tan, Jing Yuan; Sim, Jean Xiang Ying; Venkatachalam, Indumathi
title: Reduction in asthma admissions during the COVID-19 pandemic: consequence of public health measures in Singapore
date: 2021-03-02
journal: Eur Respir J
DOI: 10.1183/13993003.04493-2020
sha: 226e94070014845583d141ae92734c8e4cbca481
doc_id: 1046812
cord_uid: ykfidmzv

A sustained reduction in asthma admissions with PCR-proven respiratory viral infections coincided with the widespread adoption of public health measures, including social distancing and wearing of face coverings, during a pandemic.

We read with interest the study by Izquierdo et al. that reported a lower proportion of patients with concurrent asthma and COVID-19, compared to other chronic diseases. [1] During the ongoing pandemic, various studies have also observed a lower occurrence of persons with asthma amongst hospitalized COVID-19 cases. [2, 3] Several hypotheses have been postulated to account for these observations, including lower susceptibility to COVID-19 amongst patients with asthma [2, 3] and a remission in rates of common circulating respiratory viral infections (RVIs). [4] RVIs are potential triggers of asthma exacerbations and may cause a loss of asthma control. [5] During the COVID-19 pandemic, community-wide public health measures introduced to reduce transmission of SARS-CoV-2, such as universal masking and social distancing, may reduce community transmission of common RVIs, [4] potentially decreasing the frequency and severity of asthma exacerbations and hence reducing hospitalizations. However, patients may demonstrate a higher threshold to seek care due to fear of nosocomial transmission during the pandemic. Significant community transmission of SARS-CoV-2 may thus confound causal interpretation of trends in asthma hospitalizations. While the ongoing pandemic provides a rare opportunity to ascertain the impact of public-health measures on hospitalizations for asthma exacerbations, such observations are only possible in areas that have mitigated community transmission and maintained public-health interventions over a sustained duration. In Singapore, a Southeast-Asian city-state, various public-health interventions were implemented communitywide from February 2020. A surge of COVID-19 cases amongst migrant workers in April 2020 triggered a 7week public lockdown, with public mask-wearing being made mandatory. [4] However, the majority of COVID-19 cases remained confined to the migrant worker population staying in designated dormitories, with limited transmission in the wider community. Lockdown measures were lifted on 2 nd June 2020, with progressive relaxation of social distancing. However, compulsory mask-wearing in public places has been maintained. [4] At the largest tertiary hospital in Singapore, comprehensive infection-prevention measures prevented patient-staff transmission of SARS-CoV-2, [6] allowing admissions to continue as-usual. We evaluated trends in asthma admissions with concomitant RVIs over an unbroken 10-month period during the pandemic. From January 2018-November 2020, information on all admissions with a diagnosis of acute asthma exacerbation was extracted from our institution's electronic database. Inclusion criteria included a discharge diagnosis of acute asthma exacerbation according to appropriate ICD codes. Asthma admissions that had a PCR-proven RVI in the same admission were then identified. Pre-pandemic, patients with asthma and concurrent symptoms of upper-respiratory-tract-infection (URTI) had samples tested for common RVIs via multiplex PCR, at the physician's discretion. During the pandemic, all inpatients with URTI symptoms were additionally tested for SARS-CoV-2 as well as common RVIs. 6 The rates of asthma admissions with PCRproven RVI pre-and post-pandemic were compared using the incidence-rate-ratio method. Our results showed a significant and sustained reduction in asthma admissions with concomitant reduction in RVIs during the pandemic (Figure 1a) . The incidence rate of PCR-proven RVI was 84.2 cases per 1000asthma-admissions during the pandemic, compared with 212.6 cases per 1000-asthma-admissions prepandemic; the decline was statistically significant (incidence-rate-ratio=0.39, 95%CI=0.27-0.57, p<0.001). The total number of asthma admissions per-month dropped from an average of 64.7 (S.D=9.1) pre-pandemic to 39.2 admissions/month (S.D=7.5) during the pandemic (p<0.001) (Figure 1b) . During the pandemic, only 11.5% (33/288) of asthma admissions had a concurrent PCR-proven RVI, while one-half (53.5%, 348/651) of asthma admissions had a positive result pre-pandemic (odds ratio, OR=0.11, 95%CI=0.08-0.17, p<0.001). This decline was noted despite increased sampling, likely due to heightened vigilance for respiratory symptoms during the pandemic. During the pandemic, close to three-quarters (73.5%, 288/392) of asthma admissions were tested for RVIs, while pre-pandemic, around two-fifths (39.7%, 651/1637) of asthma admissions were tested for RVIs (OR=4.19, 95%CI=3.28-5.35), p<0.001). Notably, over a 5-month period from May-September 2020 onwards, zero asthma admissions had concomitant RVIs. This observation was unprecedented in the preceding 2 years. A sustained reduction in asthma admissions with PCR-proven RVIs coincided with the widespread adoption of public health measures during a pandemic. While a reduction in admissions could also be driven by diversion of patients away from hospitals designated for COVID-19 care, our institution was not designated as the national centre for handling COVID-19 cases and continued services as-usual. Additionally, there was no significant increase in the number of admissions with concomitant RVIs at our institution requiring intensive care, [7] suggesting no corresponding rise in case severity associated with delayed presentation. While outdoor air pollution in Singapore also significantly decreased during the lockdown period due to movement restrictions, [8] the reduction in asthma admissions was sustained for more than six months after the lifting of lockdown. The trends seen for asthma admissions mirrored observations for other chronic diseases, including chronic-obstructive-pulmonary-disease (COPD) and heart failure. [9, 10] 

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Air Quality during the COVID-19 Lockdown in Singapore and Associations with Human Mobility Trends. 2020. Aerosol and Air Quality Research

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Reduction in heart failure admissions with concomitant respiratory viral infections during the novel coronavirus disease-2019 pandemic: Unintended consequence of public health measures in Singapore