Relationship between asthma and severe COVID-19: a national cohort study

Overview

Previously, there has been conflicting evidence on how an asthma diagnosis affects the risk of severe COVID-19 cases. A new analysis of health records of 38 million people in England found that those with mild or well-controlled asthma face no higher risk of hospitalisation or death from COVID-19 compared with the general population.

The challenge

During the early stages of the COVID-19 pandemic, people deemed clinically extremely vulnerable were advised to shield themselves by avoiding contact with people outside their household. This group included people with asthma, as the respiratory nature of the disease was thought to put them at higher risk.

Since then, researchers have tried to understand the real risk faced by people with asthma. Early research relied on less reliable methods and had issues of selection bias due to increased testing of people with asthma before tests were widespread. Some of these initial results suggested that all people with asthma were at greater risk of worse outcomes. However, this research relied on assumptions to interpret the data.

The solution

Researchers funded through BREATHE, the Health Data Research Hub for respiratory health, looked at health records for 35 million adults and 3 million children to understand how COVID-19 affected people with asthma. This is the largest study of COVID-19 in asthma patients in the UK, providing more granular detail into the factors involved.

The team linked records from GPs with hospital and census data to track admissions, deaths and demographics. This information was used to determine the severity of the asthma and how well-controlled it was, for instance, by identifying the use of oral steroids or hospital admission due to an asthma attack.

Impact and outcomes

The results showed that people with mild or well-controlled asthma have no greater risk of COVID-19 hospitalisation or death compared to the general population. This suggests that these individuals should not have to take additional precautions, such as shielding.

By contrast, adults with severe asthma had a 36 per cent higher chance of COVID-19-related death and a 52 per cent increase in hospitalisation risk. In addition, children with severe asthma that was not well-controlled were almost four times more likely to be hospitalised due to COVID-19.

Professor Jennifer Quint, the senior author of the paper published in the journal Thorax, said:

“This shows how important it is to better manage underlying chronic disease. If you have mild or well-controlled asthma, your risk of having adverse outcomes is no worse than the general population. From a patient perspective, that is an important take-home message to reinforce the need for getting the right care.”

The team is continuing to analyse the data to better understand the complications that can arise following COVID-19 in people with asthma.

Impact committee

The Impact committee considered that this research had a strong relevance for clinical care for people with asthma. Although this question has been studied previously, the scale of this work provides new insights into an important area.