Could COVID-19 Increase Your Risk of Dementia?

Other infections linked to dementia

Scientists have been investigating links between infection and dementia for years, said Avindra Nath, M.D., clinical director of the National Institute of Neurological Disorders and Stroke (NINDS) at the National Institutes of Health (NIH). Research shows just one episode of an infection — you get hospitalized with pneumonia, for example — can accelerate cognitive decline, especially if you're already predisposed to memory problems.

"In general, we know that as you get older and get any kind of disease, even a urinary tract infection, it can bring out an underlying dementia,” Nath said.

Respiratory viruses in particular seem to pack a powerful neurological punch.

After the severe acute respiratory syndrome (SARS) outbreak in 2002 and the Middle East respiratory syndrome (MERS) outbreak in 2012 — both syndromes are caused by coronaviruses — 1 in 5 recovered patients reported memory impairment, according to a review in The Lancet Psychiatry.

Before that, scientists studying the 1918 influenza pandemic noted an increase in cognitive decline, psychosis and Parkinson's disease in those who had survived.

The neurological effects of COVID-19 range from mild symptoms such as headache and loss of taste and smell to more severe symptoms such as dizziness, confusion, seizures and stroke.

So-called long-haulers, the survivors of coronavirus infections whose symptoms linger, complain of headaches, fatigue, loss of taste and smell, memory loss, attention difficulties and a “brain fog” that makes it difficult for them to go about their day-to-day activities. In some patients, the problems have dragged on for months.

COVID-19 and the brain

Researchers are trying to tease out exactly how the SARS-CoV-2 virus damages the brain. Is it getting into the brain and attacking it directly? Or is the damage being caused by an inflammatory or autoimmune response?

In a paper published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, de Erausquin and his coauthors highlighted recent research that suggests the virus may directly invade the brain.

The paper noted the virus has been found in postmortem brain tissue samples and said abnormal brain imaging has emerged “as a major feature of COVID-19 from all parts of the world.”

When Nath recently used a high-resolution MRI machine to look at the brains of 19 deceased COVID-19 patients for an NIH study published Dec. 30, he saw no signs of the virus, but he did find significant blood vessel damage and inflammation.

Nath said the damage was particularly bad on the brain stem and in the olfactory bulb, which is important for the sense of smell.

"In one or two individuals, [the olfactory bulb] was so bad it was almost destroyed,” he said. “I couldn't even see the architecture of it. It makes you wonder if those areas are more involved than others, and what the consequences of that involvement might be.”

More about the study

The global study will investigate the long-term effects of COVID-19 by age, genetic traits and ethnic background. It will look at whether the virus seems to spur new disease or only accelerate disease in people who are already susceptible biologically or genetically.

Patients who experienced severe illness, as well as those who were asymptomatic, will be included, said Heather Snyder, vice president of medical and scientific relations at the Alzheimer's Association.

The study will also compare cognitive symptoms based on the type of care each patient received, Snyder said.

"We might learn that there are certain types of care that could have better outcomes not just for COVID, but for our brains,” she said.