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For decades it has been considered an infectious cause in the development of Alzheimer’s disease, without irrefutable evidence. Recently, through a study of more than 6 million older people, researchers reveal that those infected with the COVID-19 virus have a considerably increased risk (50 to 80%) of developing Alzheimer’s during the following year. This discovery updates the future needs of health systems and public health to be able to face the safe increase in dementia cases in the future.
Affecting almost 900,000 people in France according to the Pasteur Institute, Alzheimer’s disease is a progressive neurodegenerative disease. Two abnormal structures called plaques and tangles are the main suspects for brain damage related to the disease.
It is part of the plaque deposits a protein called beta-amyloid, which accumulates 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 accumulate inside cells. The latter disorganize neurons, causing neurofibrillary degeneration and then nerve cell death.
An infectious etiology has been suspected for a few years, that is, the pathology would develop after a viral infection. But despite supporting evidence, this hypothesis remains controversial. The increased risk of sequelae due to COVID-19 in people with Alzheimer’s disease and the recognition of these long-lasting neurological sequelae due to SARS-CoV-2 infection reflect in part the inflammatory processes that are at the heart of the neuropathology of Alzheimer’s disease. Alzheimer disease.
That’s why a team from Case Western Reserve University and Case Western Reserve School of Medicine in Cleveland recently wanted to know if COVID-19 could trigger Alzheimer’s disease or speed up its onset. Their study, published in the journal Journal of Alzheimer’s Diseasereveals a significantly elevated risk factor in people over 65 years of age for developing the disease within a year of infection.
More than 6 million elderly 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 medical records of 6,245,282 adults in the United States, older than 65 years, who received medical treatment between February 2020 and May 2021 and without any previous diagnosis of Alzheimer’s disease.
They then 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 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 a new diagnosis of Alzheimer’s disease in these two cohorts.
Pamela Davis, professor emeritus at the university and co-author of the study, explained in a press release: Given that SARS-CoV-2 infection has been associated with central nervous system abnormalities, including inflammation, we wanted to assess whether, even in the short term, COVID-19 could lead to an increase in diagnoses. “.
The results showed that the risk of developing Alzheimer’s disease in older adults nearly doubled (from 0.35% to 0.68%) over a one-year period after COVID-19 infection. The authors acknowledge limitations in their work, such as the possible biases introduced by the observational and retrospective nature of this study and the inaccuracy 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 onset. 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 increases significantly in people over 85 years of age and in women. The implication of these results further increases awareness of the burden that Alzheimer’s pathology represents for the entire community and health systems.
Pamela Davis explains: If this surge 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 high blood pressure, heart 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, show that monitoring Alzheimer’s pathology is essential to allow healthcare systems to be updated, as far as possible. looking to the future.
Rong Xu, corresponding author of the study, professor of biomedical informatics at the medical school and director of the Center for Artificial Intelligence in Drug Discovery, said the team plans to continue studying the effects of COVID-19 on Alzheimer’s disease and other diseases. 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.