A recent study of more than 6 million people aged 65 and over found that older people with Covid-19 had a significantly higher risk of being diagnosed with Alzheimer’s disease within a year.
The study does not show that Covid-19 causes Alzheimer’s disease, but it adds to the growing body of research linking coronavirus infection to cognitive function.
“In the Alzheimer’s disease brain, pathology begins to accumulate about 20 years before the onset of symptoms,” said Dr. David Holtzman, a neurologist who leads a research lab focused on Alzheimer’s disease. at Washington University School of Medicine in St. . Louis. People should be followed for decades after a Covid-19 infection to prove the cause, he said.
Instead, a Covid-19 infection could cause inflammation that could exacerbate changes already happening in the brain, experts say.
“The brain has its own immune response to the pathology involved in [Alzheimer’s] the disease progresses,” said Holtzman, who was not part of the new study. “When there are other things that cause inflammation in the body that can affect the brain, what’s probably happening is that it can even amplify the process that’s already going on.”
Other viruses can cause similar inflammation, experts say.
Covid “is another one of many potential risk factors that I have discussed with my patients,” said Dr. Richard Isaacson, neurologist and director of the Center for Brain Health at Florida Atlantic University. He was also not involved in the new study, but is a researcher focused on preventing the risks of Alzheimer’s disease.
“I tell people to get vaccinated against shingles. I tell people to get their annual flu and Pneumovax,” and to exercise and eat a brain-healthy diet.
Still, “when there is smoke, there is fire at some point,” he said. “I really believe it’s something to at least pay attention to.”
The latest study, published last week in the Journal of Alzheimer’s Disease, found that there were about seven new diagnoses of Alzheimer’s disease for every 1,000 older people who had a documented case of Covid-19 over the past past year, compared to about five new diagnoses for every 1,000 who did not.
Heather Snyder, vice president of medical and scientific relations at the Alzheimer’s Association, notes that broader implications of the pandemic could have played into the study results.
“The pandemic has presented serious delays for people seeking medical diagnoses like Alzheimer’s disease, which means these results could be driven by those who already had Alzheimer’s disease when they were infected but who don’t ‘had not yet sought a formal diagnosis,’ she said.
The study authors, along with Snyder and other experts, also identify this work as a call for more research into the underlying mechanisms of Alzheimer’s disease that could explain the association.
In the new study, the diagnosis of Alzheimer’s disease was “mostly tentative,” said Dr. Eliezer Masliah, director of the Division of Neuroscience at the National Institute on Aging of the National Institutes of Health.
Masliah, who was not involved in the study, said there is evidence that Covid-19 could “trigger cognitive impairment”, but there are new ways to specifically confirm the link to the disease. Alzheimer’s.
A next step would be to follow people at risk of Alzheimer’s disease long-term after Covid-19 infection to track biomarkers found in blood and brain scans.
“In the next two years, we’re going to have a lot of very important information,” Masliah said. And it’s an “extremely important issue” to watch, given the scale of the disease.
“Imagine how many millions of people over 60 or 65, like me, have had Covid. Let’s say 5% of them or 10% of them or even 1% of them are at risk,” he said.
“Wow. We are looking at a lot of people over the next few years who could be added to the already very large epidemic of Alzheimer’s disease that we have.”
About 6.5 million people over the age of 65 live with Alzheimer’s disease, according to estimates by the Alzheimer’s Association. And it was the seventh leading cause of death in the United States in 2020, according to data from the United States Centers for Disease Control and Prevention.
“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” , said research professor Dr. Pamela Davis. at Case Western Reserve University and co-author of the new study.
“Now so many people in the United States have had Covid, and the long-term consequences of Covid continue to emerge. It is important to continue to monitor the impact of this disease on future disability.