A recent study of more than 6 million people 65 and older found that seniors who had Covid-19 had a substantially higher risk of being diagnosed with Alzheimer’s disease within a year.
The study does not show that Covid-19 causes Alzheimer’s, but it adds to the growing body of research drawing links between coronavirus infection and cognitive function.
“In the Alzheimer’s disease brain, the pathology starts to build up about 20 years before the symptoms begin,” said Dr. David Holtzman, a neurologist who leads a research lab focused on Alzheimer’s disease at the Washington University School of Medicine in St. Louis. People would have to be followed for decades after a Covid-19 infection to prove it as a cause, he said.
Instead, a Covid-19 infection could cause inflammation that may exacerbate changes that are already happening in the brain, experts say.
“The brain has its own immune response to the pathology that’s involved in [Alzheimer’s] disease progressing,” said Holtzman, who was not part of the new study. “When there are other things that cause inflammation that are in the body that can affect the brain, likely what happens is that can even amplify the process that’s already going on.”
Other viruses can cause similar inflammation, experts say.
Covid “is another one of the many dozen potential risk factors that I talked about with my patients,” said Dr. Richard Isaacson, a neurologist and director of Florida Atlantic Unviersity’s Center for Brain Health. He also was not involved in the new study but is a researcher focused on risk prevention for Alzheimer’s disease.
“I tell people to get a shingles vaccine. I tell people to get their annual flu and Pneumovax,” and to exercise and eat a brain-healthy diet.
Still, “when there’s smoke, there’s fire at some point,” he said. “I really believe that this is 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 seniors who had a documented case of Covid-19 in the past year, compared with 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’s findings.
“The pandemic presented serious delays for individuals seeking out medical diagnoses like Alzheimer’s, meaning these results could be driven by those who already had Alzheimer’s when they were infected but had not yet sought out a formal diagnosis,” she said.
The study authors, along with Snyder and other experts, also identify this work as a call for more research on the underlying mechanisms of Alzheimer’s disease that might explain the association.
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