A study published this morning has revealed that having two copies of the e4 variant of the ApoE gene doubles your risk of developing severe COVID-19 symptoms. Researchers have been turning to genetics since it became evident that symptom severity varies widely from a mild cough and fever, to severe respiratory disease that requires ventilation.
This study comes after the National Statistics showed that dementia is a leading underlying condition in patients who have died of COVID-19, and may help to explain the link. David Melzer, co-author of the study and professor of epidemiology said, “this is an example of a specific gene variant causing vulnerability in some people”.
They analysed data from the UK biobank and focused on the ApoE gene, the protein it transcribes to is involved in carrying fat around the body, and the “e4” variant is known to affect cholesterol levels and inflammation, increasing the risk of heart disease and dementia. They found 9,022 Biobank participants of European ancestry who had two copies of the e4 variant, while more than 223,000 had two copies of an “e3” variant. Having 2 copies of the e4 variant equals a 14-fold increased risk of dementia compared to e3.
The team then looked at positive test results for Covid-19 in March when testing was carried out in hospitals, indicating the cases were severe. The results revealed 37 people who tested positive for the virus had two copies of the e4 variant, while 401 had two copies of the e3 variant. After considering factors such as age and gender, the team found that those with two e4 variants had over double the risk of developing severe COVID-19 symptoms than those with two e3 variants.
Melzer then added that the results were not down to people with the e4 variants being more likely to be living in a care home – the association remained when the team excluded participants with a dementia diagnosis, and none of the COVID-19 positive participants with two e4 variants had a dementia diagnosis.
However, further research is needed to understand the link between the allele and COVID-19 symptoms. Professor Tara Spires-Jones, an expert in neurodegeneration at the University of Edinburgh was not involved in the study but said that the link between the ApoE gene and COVID-19 symptoms was robust, however, it doesn’t prove that the gene itself causes more severe symptoms.