A new study is the latest to suggest genetics and not just age may play a role in why some people are more vulnerable to the coronavirus than others.
It could explain why people with dementia have been hard hit: dementia is one of the most common underlying health conditions among those who have died from COVID-19 in England and Wales.
“It is not just age: this is an example of a specific gene variant causing vulnerability in some people,” said David Melzer, a professor of epidemiology and public health at Exeter University and a co-author of the study.
The report is based on research that analysed data from the UK Biobank, a research endeavour that has collected genetic and health data on 500,000 volunteers aged between 48 and 86.
According to the Guardian, the team focused on a gene called ApoE – this gives rise to proteins involved in carrying fats around the body. One such variant, called “e4”, is known to affect cholesterol levels and processes involved in inflammation, as well as increasing the risk of heart disease and dementia.
The researchers found 9,022 of almost 383,000 Biobank participants had two copies of the e4 variant, while more than 223,000 had two copies of a variant called “e3”. The former, the team add, have a risk of dementia up to 14-fold higher than the latter.
The team then looked at positive tests for COVID-19 between 16 March and 26 April when testing for the coronavirus was largely carried out in hospitals, suggesting the cases were severe.
The results reveal 37 people who tested positive for COVID-19 had two copies of the e4 variant of ApoE, while 401 had two copies of the e3 variant. After taking into account various factors, including age and sex, the team say people with two e4 variants had more than double the risk of severe COVID-19 than those with two e3 variants.
“It is pretty bulletproof – whatever associated disease we remove, the association is still there. So, it looks as if it is the gene variant that is doing it … This association is not driven by people who actually have dementia,” said Melzer.
But Prof David Curtis, honorary professor at the UCL Genetics Institute, urged caution.
“I’m afraid this study does not really convince me that the gene variant is really an independent risk factor for severe COVID-19 infection,” he said.
“I would want to see this tested in a sample where dementia could be more confidently excluded, perhaps a younger cohort. I am sure additional data will soon emerge to illuminate this issue.”
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