Elderly subjects who have contracted Covid-19 are more likely to develop Alzheimer’s disease in the year following their contamination. This is observed by a large study conducted using data from more than 6,200,000 people over the age of 65.
Since the start of the epidemicresearchers around the world are trying to understand the potential long-term effects of infection with the Covid-19. Recently, researchers from Case Western River University in the United States looked at the impact of SARS-CoV-2 on the elderly. To do this, they analyzed the health data of more than 6,200,000 subjects aged 65 and over, followed in 68 health centers distributed in the 50 states of the United States in 2020 and 2021. Among them, 410,000 had contracted Covid-19.
Published in the Journal of Alzheimer’s Disease on September 13, the study revealed that seniors were more likely to develop Alzheimer’s disease in the year following their contamination by SARS-CoV-2. A risk increased by 89%, according to the authors’ estimates.
Is there a link between Covid-19 and Alzheimer’s?
How to explain that a respiratory infection such as Covid-19 can have impacts on the brain and lead to a neurodegenerative disease such as Alzheimer’s? We put the question to Hélène Amieva, professor of Universities in Psychogerontology and member of the Scientific Council of the B2V Observatory of Memories. “It is an epidemiological study, a very useful method to raise warning points but which does not always give explanations of such and such a link”she says. “The study therefore does not make it possible to establish a link between Covid-19 and Alzheimer’s. The association is plausible because SARS-CoV-2 is known to be a neurotropic virus, i.e. it penetrates the brain, which is not the case for all viruses. It enters the nasal or oral passages, that’s where it gets to the brain.” Other hand, “we know thanks to brain imaging data that the Covid can create brain damage”.
“What we don’t know and what the study doesn’t demonstrate is whether it’s a direct or indirect link.” If it’s a direct link, it means “the brain damage created by SARS-CoV-2 will make the bed”, by a succession of events and chemical processes, to a degeneration of neurons. On the contrary, the link might be indirect. “The older we are, the more we have a weakened brain due to several factors, for example cardiovascular or inflammatory lesions. He becomes more vulnerable to neurodegenerative diseases.” The hypothesis, in a very colorful way, is that infection with Covid-19 weakens the brain by adding lesions, and therefore makes it doubly vulnerable to diseases such as Alzheimer’s.
“Maybe Covid-19 rushed things”
Pr. Hélène Amieva recalls that there are multiple risk factors to develop this disease: age, social and cultural aspects, social isolation, low physical activity, the presence of cardiovascular factors, the genetic aspect have been demonstrated by science. There are still others to discover. “Pathology takes years to develop. People were not without anything and overnight, due to Covid-19, had Alzheimer’s. It first manifests itself in discreet disorders and then there is an increase in the symptoms, but this happens over decades. People followed during the study “were probably already on the path to illness. Maybe the Covid-19 rushed things, this is the hypothesis of this paper”.
It is not excluded that Covid-19 causes or accelerates the development of other neurological diseases since once once more the virus manages to infiltrate the brain, “but no one can say that”. “Studies are underway. This shows the importance of following people who have been infected, especially those who have developed significant and especially persistent symptoms, to see if they are precisely inclined to develop a particular disease. For the time being, we do not have enough hindsight.
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