A recent study published in the Journal of Alzheimer's Disease found that seniors with Covid-19 had a greater risk of receiving a new Alzheimer's diagnosis within a year—but some experts cautioned the symptoms of long Covid could be misinterpreted as Alzheimer's disease, Mark Johnson reports for the Washington Post.

Study details

For the study, researchers from Case Western Reserve University School of Medicine looked at the electronic health records of more than six million Americans over the age of 65 using a database that represents patients from nearly 70 health care centers nationwide.

Specifically, the researchers focused on patients over the age of 65 who had a medical visit between Feb. 2, 2020, and May 30, 2021. They then divided those patients into two groups—those who had been diagnosed with Covid-19 and those who hadn't.

The researchers found that for every 1,000 seniors who had been diagnosed with Covid-19, seven would be diagnosed with Alzheimer's disease within a year. Meanwhile, for every 1,000 seniors not diagnosed with Covid-19, five would receive an Alzheimer's diagnosis within a year.

However, the researchers acknowledged one limitation of the study was the potential for inaccurate Alzheimer's diagnoses, especially since for much of the study period, the electronic health system did not have a code for long Covid, meaning it's possible long Covid patients could have been misdiagnosed with Alzheimer's.

Discussion

Rong Xu, a research professor at Case Western Reserve, said she had anticipated seeing an increase in Alzheimer's diagnoses among seniors with Covid-19, but was surprised "by the extent of the increase and how rapidly it occurred."

Thomas Wisniewski, director of the NYU Langone Alzheimer's Disease Center, said it's possible that some patients could already be on the path towards Alzheimer's and, when they get Covid-19, their brains "take a second hit."

Wisniewski added that researchers should look at whether biomarkers for Alzheimer's that appear in Covid-19 patients "stay increased over time, and do they result in a faster disease trajectory?"

Gabriel de Erausquin, director of the Laboratory of Brain Development, Modulation, and Repair at the University of Texas Health San Antonio, said he felt the study was "important and useful" but also "limited."

He noted that an Alzheimer's diagnosis isn't always confirmation of the disease, and that some doctors will diagnose Alzheimer's based on behavioral changes or responses to a memory test. Those diagnoses are considered less accurate than ones based on spinal fluid or imaging tests that measure beta-amyloid and phosphorylated tau proteins, which abnormally accumulate in the brains of Alzheimer's patients, de Erausquin said.

"You have people who very much look like they have Alzheimer's, but they do not have Alzheimer's," he said, adding that "[p]eople who have long Covid are at risk of being diagnosed with Alzheimer's disease."

However, Pamela Davis, a co-author of the study and a research professor at Case Western Reserve, said she doesn't believe doctors are likely to misdiagnose a long Covid patient with Alzheimer's.

"To label somebody with Alzheimer's disease is different from the brain fog and the confusion associated with long covid," she said. "When a physician makes a diagnosis of Alzheimer's disease, it represents a substantial cognitive impairment." (Johnson, Washington Post, 9/16)