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Those with a genetic mutation which raises the risk of dementia may also have a greater chance of suffering severe COVID-19, The Guardian reported, quoting a new study published in the Journal of Gerontology: Medical Sciences says.

"This is an example of a specific gene variant causing vulnerability in some people," explained Professor David Melzer, an expert in public health and epidemiology at Exeter University and co-author of the study.

The study analyzed genetic and health data from the UK Biobank on 500,000 volunteers ages 48-86, and focused on the ApoE gene. One variant of the gene, known as "e4," affects cholesterol levels and the process surrounding inflammation, and also increases the risk of heart disease and dementia.

The study looked at 9,022 participants of European ancestry who had two copies of the e4 variant, along with over 223,000 who had two copies of the e3 variant.

Those with two copies of the e4 variant had a risk of dementia up to 14 times higher than those with two copies of the e3 variant. In the study, 37 people who tested positive for COVID-19 had two copies of the e4 variant, while 401 had two copies of the e3 variant. After controlling for other factors, those with two copies of the e4 variant had over double the risk of severe coronavirus than those with two copies of the e3 variant.

This association remained even when those participants who suffered dementia were excluded from the analysis: None of the coronavirus-positive participants had been diagnosed with dementia, Melzer said.

"It is pretty bulletproof – whatever associated disease we remove, the association is still there," Melzer said. "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," he added. "The effect could be partly due to this underlying genetic change, which puts them at risk for both COVID-19 and dementia.

Both in the sample size and the population at large, the majority of people have not yet been exposed to coronavirus, the researchers said..