Gene that increases risk of Alzheimer’s ‘also raises chance of severe Covid’

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Dementia - Westend61

Dementia – Westend61

A gene that increases the risk of Alzheimer’s disease also raises the chance of developing severe Covid, scientists have found in new research which helps explain why coronavirus in care homes was so deadly.

Researchers at University College London (UCL) discovered that the variants of the gene OAS1 raised the baseline risk of Alzheimer’s by up to 22 per cent, while also increasing the chance of requiring intensive care for Covid-19 by as much as 20 per cent.

Dementia is the main pre-existing health condition associated with Covid-19 mortality, and in the early stages of the pandemic last spring it was a factor in one in four coronavirus deaths.

Initially, experts believed the link was due to people with dementia being older, less able to adhere to social distancing and mask wearing, and being subjected to increased exposure in care homes.

But the new research suggests that underlying genetics may also have played a role.

The gene responsible is linked to the immune system and determines how many pro-inflammatory proteins are released in the body. Scientists think it may be responsible for the deadly cytokine storm which some people experience after developing Covid.

‘Same immune system changes can occur in Alzheimer’s disease and Covid-19’

Lead author Dr Dervis Salih, of the UK Dementia Research Institute at UCL, said: “While Alzheimer’s is primarily characterised by harmful build-up of amyloid protein and tangles in the brain, there is also extensive inflammation in the brain that highlights the importance of the immune system in Alzheimer’s.

“We have found that some of the same immune system changes can occur in both Alzheimer’s disease and Covid-19.

“In patients with severe Covid-19 infection, there can also be inflammatory changes in the brain. Here we have identified a gene that can contribute to an exaggerated immune response to increase risks of both Alzheimer’s and Covid-19.”

The new variant is present in over half of Europeans and it has a bigger impact on Alzheimer’s risk than several known risk genes.

For people aged 85 and over, the risk of developing Alzheimer’s is around 30 per cent and the gene increases the chance to between 33 and 36 per cent chance.

The researchers believe that testing for the gene and its variants could indicate who was at greater risk from Covid.

‘Shared genetic risk factor at play’

Doctoral student Naciye Magusali, of UCL, said: “Our findings suggest that some people may have increased susceptibility to both Alzheimer’s disease and severe Covid-19, irrespective of their age, as some of our immune cells appear to engage a common molecular mechanism in both diseases.”

Commenting on the study, Dr Rosa Sancho, head of research at Alzheimer’s Research UK, said: “Fairly early in the pandemic, people with dementia emerged as a group at particular risk of severe Covid-19 infection.

“While there are likely to be several reasons for this, the study raises the possibility of a shared genetic risk factor playing a role.”

Prof Jonathan Schott, professor of neurology at UCL, said: “While some of this excessive mortality may relate to people with dementia being overrepresented in care homes which were particularly hard hit by the pandemic, or due to general increased vulnerability to infections, there have been questions as to whether there are common factors that might increase susceptibility both to developing dementia and to dying from Covid-19.

“The identification of a genetic risk factor and elucidation of inflammatory pathways through which it may increase risk has important implications for our understanding of both diseases, with potential implications for novel treatments.”

The research was published in the journal Brain.

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