A new study has said that people who have had a case of Covid-19 no matter how mild may have accelerated aging of the brain and even increased chances of having dementia or Alzheimer's.
The study, published Monday, March 7, in the journal Nature, is believed
to be the largest of its kind and it found that the brains of those who
had Covid-19 had a greater loss of gray matter and abnormalities in the
brain tissue compared with those who didn't have Covid-19.
The study showed that many of those changes were in the area of the brain related to the sense of smell.
"We were quite surprised to see clear differences in the brain even with
mild infection," lead author Gwenaëlle Douaud, an associate professor
of neurosciences at the University of Oxford.
Dr Douaud and her colleagues checked brain imaging photos from 401
people who had Covid-19 between March 2020 and April 2021, both before
infection and an average of 4½ months after infection.
They compared the results of the 401 people with brain imaging of 384
uninfected people similar in age, socioeconomics and risk factors such
as blood pressure and obesity. Of the 401 infected people, 15 had been
hospitalized.
Douaud explained that it is normal for people to lose 0.2% to 0.3% of
gray matter every year in the memory-related areas of the brain as they
age, but in the study evaluation, people who had been infected with the
coronavirus lost an additional 0.2% to 2% of tissue compared with those
who hadn't been infected, a startling discovery.
In addition to imaging, the study participants were tested for their executive and cognitive function.
Using the Trail Making Test, the participants were tested for cognitive
impairments associated with dementia and brain processing speed and
function tests. The researchers found that those who had the greatest
brain tissue loss also performed the worst on this exam.
"Since the abnormal changes we see in the infected participants' brains
might be partly related to their loss of smell, it is possible that
recovering it might lead to these brain abnormalities becoming less
marked over time. Similarly, it is likely that the harmful effects of
the virus (whether direct, or indirect via inflammatory or immune
reactions) decrease over time after infection. The best way to find out
would be to scan these participants again in one or two years' time,"
she said...
Douaud added that the researchers anticipate reimaging and testing the participants in one or two years. And while the study finds some association between infection and brain function, it's still not clear why.
The authors cautioned that the findings were only of a moment in time
but noted that they "raise the possibility that longer-term consequences
of SARS-CoV-2 infection might in time contribute to Alzheimer's disease
or other forms of dementia."
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