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People with dementia are twice as likely to catch the coronavirus, a study has suggested.
Early research implied the infection is mild in four out of five cases, however, it can trigger a disease called COVID-19. Like dementia, these complications are more common among the elderly.
Many care homes were hit by coronavirus outbreaks at the start of the pandemic, leaving dementia patients particularly vulnerable to catching the infection.
After taking this into account, scientists from Case Western Reserve University in Ohio have reported dementia patients still face double the risk of catching the coronavirus as someone without the memory-robbing disorder.
Although unclear, dementia patients may not remember to maintain social distancing, wear a face covering or wash their hands regularly, according to the scientists.
Severe cognitive decline can also damage a patient's blood brain barrier, allowing certain viruses and bacteria to reach the vital organ more easily, they added.
The results further reveal the coronavirus-dementia patients were over four times more likely to die in the next six months than people with the infection but not the memory-robbing disease.
"Folks with dementia are more dependent on those around them to do the safety stuff; to remember to wear a mask, to keep people away through social distancing,” said Dr Kenneth Langa, from the University of Michigan, as reported by The New York Times.
"There is the cognitive impairment and the fact they are more socially at risk."
Dementia is an umbrella term for conditions that cause a progressive loss of brain function, of which Alzheimer's is the most common.
To better understand how dementia may be linked to the coronavirus, the Ohio scientists analysed the electronic health records of 61.9 million adults in the US up to August 2020.
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Overall, the results – published in the journal Alzheimer's & Dementia – suggest dementia patients are twice as likely to catch the coronavirus.
Those with vascular dementia appear to be worst affected, with the risk rising by more than three times. Vascular dementia occurs when blood flow to the brain is reduced.
Pre-senile dementia and Alzheimer's patients have a 2.6 and 1.8 times heightened risk, respectively, the results suggest.
Pre-senile dementia is defined as any form of the condition that affects someone under 65. Alzheimer's is thought to be caused by the abnormal build-up of proteins in and around brain cells.
Post-traumatic dementia, after a brain injury, was linked to 1.6 times higher risk of catching the coronavirus.
Throughout the pandemic, statistics have repeatedly flagged Black people are more likely to catch and become seriously ill with the coronavirus than their white counterparts.
When it comes to dementia, Black people were found to face a 2.8 times higher risk of developing the infection.
They were also more likely to be hospitalised, but did not have a higher death risk. The scientists noted this may be due to the small number of relevant deaths not allowing firm conclusions to be drawn.
The overall results remained the same after the team accounted for the participants' age, sex, ethnicity, underlying health, nursing home stay and any organ transplant procedure; all of which can influence a person's risk of testing positive for the coronavirus.
Dr Langa noted the results are based on electronic health records and may therefore not include "more isolated and poorer patients that have a harder time getting to doctors", suggesting the findings could be an "underestimate".
The coronavirus is known to affect the brain, demonstrated by a tell-tale symptom being a loss of smell or taste.
In July 2020, an expert even warned it “remains to be seen” whether the infection causes the same brain damage as Spanish flu.
The 1918 pandemic left some patients enduring viral encephalitis, brain swelling that can occur if an infection enters the central nervous system.
Some survivors went on to develop viral Parkinsonism, defined as symptoms similar to Parkinson’s disease, like shaking and stiff movements.
When it comes to dementia, past research has suggested damage to a patient's blood brain barrier leaves them more susceptible to herpes, pneumonia and gum disease, according to the Ohio scientists.
Any pre-existing damage may "permit greater virus entry into the brain".
This could trigger inflammation and blood clotting that is excerbated by reduced oxygen levels and organ failure in other parts of the body, added the scientists.
The degree of damage may vary between different types of dementia, which could explain why patients face a varied risk.
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