Covid-19 in older people linked to increased risk of Alzheimer’s, study finds

A study using the electronic health records of more than 6 million Americans over the age of 65, found those with covid-19 ran a greater risk of being re-diagnosed with Alzheimer’s disease within a year.

The studyled by researchers at Case Western Reserve University School of Medicine and published in the Journal of Alzheimer’s Disease, does not show that covid-19 causes Alzheimer’s disease, but adds to a growing number of works suggesting links between the two.

The findings suggest researchers should follow older patients recovering from covid to see if they continue to show signs of memory loss, declining brain function or Alzheimer’s disease. The study found that for every 1,000 older people with covid-19, seven will be diagnosed with Alzheimer’s within a year, slightly above the five in a thousand diagnosis rate for older people who don’t. had no covid.

“We know covid can affect the brain, but I don’t think anyone has looked at new Alzheimer’s diagnoses,” said Pamela Davis, one of the study’s co-authors and research professor. at Case Western Reserve University School of Medicine. Colleague Rong Xu said she expected to see some increase among older people sick with covid, but was surprised “by the magnitude of the increase and how quickly it happened”.

The study, while “important and useful” was “limited,” said Gabriel de Erausquin, director of the Brain Development, Modulation and Repair Laboratory at the University of Texas Health San Antonio, who did not did not participate in the research.

He warned that a diagnosis of Alzheimer’s disease is not necessarily confirmation of the disease. Doctors sometimes diagnose Alzheimer’s disease based on changes in behavior or responses to a memory test. These are considered less accurate than imaging or cerebrospinal fluid tests which measure two types of proteins, beta-amyloid and phosphorylated tau, which accumulate abnormally in the brains of people with the disease of Alzheimer’s. Another more accurate indicator is brain scans that look for structural changes, such as certain regions shrinking.

“You have people who look a lot like Alzheimer’s disease, but they don’t have Alzheimer’s disease,” de Erausquin said, adding, “People who have had a long history of covid are at risk of being diagnosed with Alzheimer’s disease.”

In their paper, the Case Western Reserve researchers acknowledged that the study was limited by the potential for inaccurate diagnoses of Alzheimer’s disease.

Davis, however, said she thought doctors were unlikely to confuse long covid with Alzheimer’s disease.

“Labelling someone with Alzheimer’s disease is different from the brain fog and confusion associated with long covid,” she said. “When a doctor makes a diagnosis of Alzheimer’s disease, it represents a significant cognitive impairment.”

The Case Western Reserve study used a database representing patients from nearly 70 health care centers across the country. The scientists focused on patients over the age of 65 who had a medical visit during a 15-month period from February 2, 2020 to May 30, 2021, dividing them into two groups: those diagnosed with covid-19 and those without covid diagnosis.

For much of the study period, the electronic registration system did not include a code for long covid, leaving open the possibility that patients who had persistent health problems after their bout with covid were misdiagnosed with Alzheimer’s disease.

Still, the new study adds to a growing body of research examining the relationship between covid-19 and Alzheimer’s disease. A previous study by some of the same Case Western Reserve researchers looked at the electronic health records of nearly 62 million Americans over the age of 18 and found that patients with dementia had a significantly higher risk of covid-19 than patients without dementia.

Thomas Wisniewski, director of the NYU Langone Alzheimer’s Disease Center, raised the possibility that some patients are already on their way to Alzheimer’s when they get covid-19 causing their brains to “take a second hit”.

He said scientists need to determine if biomarkers of Alzheimer’s that appear in patients with covid-19 “remain increased over time and lead to a more rapid disease trajectory?”

Scientists from Columbia University Vagelos College of Physicians and Surgeons studied The brains of a small number of patients who died from covid-19 and found they had defective receptors considered an indicator of Alzheimer’s disease.

A second study examined serum, a component of blood, from hospitalized covid-19 patients with no history of dementia and they had developed markers of neurodegenerative disease at levels comparable to those found in patients with Alzheimer’s disease.

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