How Does COVID Affect Memory? Exploring the Link Between COVID and Dementia

Most people recover from COVID-19 within a couple of weeks without any long-term symptoms. But many people continue to experience memory problems or cloudy thinking, even without other symptoms of long COVID. And these neurological symptoms can last for weeks to months after infection. 

This has caused some people to wonder if COVID can lead to permanent changes in brain function — or even cause dementia. Let’s look at the research on the link between COVID and dementia.

COVID and memory loss

COVID can affect memory and other brain functions during or after the illness. Even people who had a mild case will sometimes have “brain fog” as they recover. This makes it hard for them to focus, remember things, or think on their feet. 

There are some different theories as to why this happens. 

In one study, people who had trouble with mental tasks 2 months after a mild infection also had decreased oxygen in the blood. So it’s possible that their brain is not functioning normally because their oxygen levels are still abnormal. These symptoms may also come from the inflammation of nerve cells caused by the body’s immune response.

The risk of brain impairment increases with more severe infections. One study looked at the brains of older adults who died from severe COVID. Inflammation and a lack of oxygen had significantly damaged nerve cells in the brain.

COVID and dementia

Experts don’t believe COVID can directly cause dementia. In a large review study of the existing research, there was no clear evidence that COVID causes dementia. But it’s possible that COVID might unmask or speed up changes already happening in the brain. 

In the U.S., around 15% of adults older than 68 years have diagnosed dementia. But the symptoms may be mild and slow at first, so dementia isn’t always diagnosed right away. 

After COVID, symptoms of dementia are more likely to occur in older adults who have risk factors for dementia. In one study of adults 65 and older in the U.S., Alzheimer’s disease was diagnosed more often within 1 year of having COVID. The risk was highest in those older than  85 years and in women. 

The other risk factors for dementia include:

• Age older than 65 years: This is the biggest risk factor.

• Sex: Alzheimer’s disease is more common in females. But this is not true for other types of dementia.

• Race and ethnicity: Alzheimer’s disease is more common in Black and Hispanic people.

• Genetics: Researchers have discovered a few inheritable genes that increase someone’s risk of Alzheimer’s. 

• Health conditions: Diabetes, high cholesterol, and high blood pressure are all associated with increased dementia risk. Mental health conditions like depression are also linked to increased risk.

• Substance use: Alcohol, tobacco, and recreational drug use (like cocaine) can increase someone’s risk of dementia.  

But research shows that COVID causes very real changes in the brain, which means it can have effects on memory and thinking. 

One study looked at adults ages 51 to 81 in the U.K. A brain scan done 4 months after COVID showed a loss of nerve cells and brain volume. These people also had more trouble with thinking and memory at the time of the second scan. But it’s still unclear if this leads to dementia down the line.

Long COVID and dementia

Long COVID can cause symptoms that are similar to dementia. If you or someone you know has had long COVID, you may know about “brain fog.” Cloudy thinking can happen with different medical conditions, including COVID and dementia. It’s harder to concentrate and remember tasks or recent events. It can also be harder to do more than one thing at a time. 

At any age, long COVID may cause trouble with thinking or memory for weeks or months. But memory symptoms may be worse for older adults. In one study of older adults, people with a prolonged loss of smell after COVID also had more problems with brain function. 

COVID vaccine and dementia

There’s no evidence that any of the COVID vaccines increase the risk for dementia. They also don’t make dementia symptoms worse for people who have it. The vaccines help the body fight the virus if you come into contact with it. So they actually help to lower the risk of COVID affecting the brain.

Steps to prevent memory changes if you’ve had COVID

If you’ve had COVID, the best way to prevent problems with thinking and memory is to keep your brain and body healthy. Here are some steps you can take:

• Stay physically active and get regular exercise.

• Stay mentally active with things like books, thinking games, and socialization.

• Don’t smoke.

• Eat a healthy diet with plenty of fruits, vegetables, and healthy fats.

• Avoid too much alcohol.

• Check in with your healthcare provider about blood pressure, cholesterol, and glucose.

• Talk with your healthcare provider — or anyone you trust — if you’re feeling sad or depressed.

Even if you’ve had COVID, stay up to date on vaccines and preventive measures. This helps to prevent stress on the brain and body from another bout with the virus. And if you’re worried that symptoms might be early signs of dementia, don’t hesitate to reach out to your healthcare provider with questions.

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Written by:

Anne Jacobson, MD, MPH

Anne Jacobson, MD, MPH has been a board-certified family physician since 1999. She worked as a full-scope family physician (inpatient, outpatient, obstetrics, and office procedures) in the Cook County Ambulatory Health Network for 15 years.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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