An infectious cause in the development of Alzheimer’s disease has been considered for decades, without irrefutable proof. Recently, through a study of more than 6 million elderly people, researchers revealed that those infected with the COVID-19 have a considerably higher risk (50 to 80%) of developing Alzheimer’s during the following year. This discovery updates the future needs in healthcare systems and public health in order to be able to deal with the certain increase in cases of dementia in the future.
Affecting nearly 900,000 people in France according to the Pasteur Institute, the disease d’Alzheimer is a progressive neurodegenerative disease. Two abnormal structures called plaques and tangles are prime suspects in disease-related brain damage.
It’s part plaque deposits of a piece of protein called beta-amyloid, which builds up in the spaces between nerve cells. This buildup is toxic to nerve cells. On the other hand, tangles of twisted fibers of another protein called tau build up inside cells. The latter disorganize the neurons, causing neurofibrillary degeneration and then the death of nerve cells.
For several years, a infectious etiology is suspected, i.e. the pathology would develop after a viral infection. But despite supporting evidence, this hypothesis is still controversial. The increased risk of sequelae due to COVID-19 in people with Alzheimer’s disease and the recognition of these neurological sequelae lasting due to infection with SARS-CoV-2 partly reflect the inflammatory processes that are central to the neuropathology of Alzheimer’s disease.
That’s why recently a team from Case Western Reserve University and Case Western Reserve School of Medicine in Cleveland wanted to know if COVID-19 could trigger Alzheimer’s disease or hasten its onset. Their study, published in the journal Journal of Alzheimer’s Diseasereveals a significantly elevated risk factor in people over the age of 65 for developing the disease within a year of becoming infected.
More than 6 million elderly people studied
To establish the presence or absence of a causal link between infection with the COVID-19 virus and the onset of Alzheimer’s disease, the authors analyzed the anonymous electronic health records of 6,245,282 adults in the United States, aged 65 and over, who received medical treatment between February 2020 and May 2021 and without any prior diagnosis of Alzheimer’s disease.
Then, they divided this population into two groups: the “COVID-19 cohort”, made up of people who contracted COVID-19 during this period, and the “non-COVID-19 cohort”, made up of people who had no cases. documented of infection. More than 400,000 people were enrolled in the COVID-19 study group, while 5.8 million were in the uninfected group. The authors examined the risks of new diagnosis of Alzheimer’s disease in these two cohorts.
Pamela Davis, professor emeritus of the university and co-author of the study, explains in a communiqué : « Given that SARS-CoV-2 infection has been associated with central nervous system abnormalities, including inflammation, we wanted to test whether, even in the short term, COVID-19 could lead to increased diagnoses ».
The results showed that the risk of developing Alzheimer’s disease in older adults almost doubled (from 0.35% to 0.68%) over a period of one year after COVID-19 infection. The authors recognize limitations to their work such as the potential biases introduced by the observational and retrospective nature of this study and the imprecision of the diagnosis of Alzheimer’s disease, although this does not substantially alter the main results.
In addition, the authors believe that it is not clear whether COVID-19 actually triggers Alzheimer’s disease or rather accelerates its emergence. Therefore, it is essential to provide validation from other data sources.
A growing threat to public health
In addition, the researchers found that the risk of developing this dementia is significantly increased in people over the age of 85 and in women. The implication of these results raises even more awareness of the burden that Alzheimer’s pathology represents for the entire community and healthcare systems.
Pamela Davis explains: If this increase in new Alzheimer’s disease diagnoses continues, the wave of patients with an incurable disease will be large and could further strain our long-term care resources. “. She adds : ” Alzheimer’s disease is a serious and difficult disease, and we thought we had reversed some of the trend by reducing general risk factors such as l’hypertensionheart disease, obesity and a sedentary lifestyle ».
But these results, linked to the growing number of people affected by COVID-19 and the long-term effects of this infection, demonstrate that monitoring Alzheimer’s pathology is essential to allow an upgrade, as much as possible. , care systems for the future.
Rong Xu, corresponding author of the study, professor of biomedical informatics at the medical school and director of the Center for AI in Drug Discovery, said the team plans to continue studying the effects of COVID-19 on the Alzheimer’s disease and other neurodegenerative disorders — particularly which subpopulations may be more vulnerable — and the possibility of repurposing FDA-approved drugs to treat the long-term effects of COVID-19.