A surprising amount of people still report having issues with memory and "brain fog" for weeks or months after a COVID-19 infection. And for some, these issues can be severe enough to impact their work or social lives.
New research offers more insights into the biological mechanisms that may be behind these persistent cognitive symptoms. The study, published this week in Nature, suggests that even mild COVID-19 can actually damage the brain.
COVID-19 can damage the brain
For the new study, researchers looked at brain scans for 785 participants in the UK Biobank research project. Of those, 401 people got COVID-19 and received two brain scans: one before their infection and one five (on average) after the infection. The majority of these patients had mild COVID-19 and were not hospitalized.
The researchers compared these brain scans to those of 384 control participants did not get COVID-19.
Their results showed that people who'd gotten coronavirus infections tended to have less gray matter in their brains compared to those who didn't get COVID-19, especially in areas of the brain associated with smell and memory.
This amount of damage is equivalent to about one year of normal aging, Gwenaëlle Douaud, lead author on the study and associate professor in the Nuffield Department of Clinical Neurosciences at the University of Oxford, told NBC News. Douaud noted that these changes may be reversible. "But it is still relatively scary because it was in mildly infected people,” she said.
The new research is "pretty consistent with what we're seeing across studies," Jacqueline Becker, clinical neuropsychologist and assistant professor of medicine at the Icahn School of Medicine at Mount Sinai, told TODAY.
It suggests that COVID-19 can have effects in different parts of the brain, "but it doesn't quite get at why it's happening," she said, adding that there are a few theories out there right now, some more controversial than others. One of the leading hypotheses, which the new study helps support, is that the virus causes inflammation in the brain, which may lead to damage and downstream neurological problems.
How common are cognitive symptoms after COVID-19?
Some of the more common cognitive symptoms that doctors see after COVID-19 have to do with executive dysfunction issues, said Becker, who also evaluates and treats patients at Mount Sinai’s Center for Post-COVID Care.
Under normal circumstances, your executive functioning acts like "the CEO of the brain," she explained. "It helps us organize information and problem-solve and multi-task." When those processes aren't functioning as well, you might have issues starting or ending tasks on time, for instance.
Many patients report having issues with memory, James C. Jackson, director of behavioral health at the Vanderbilt ICU Recovery Center, told TODAY. But what feels like a memory problem may actually have more to do with challenges in executive functioning, attention or processing speed, he said.
These symptoms may amount to what we colloquially refer to as "brain fog," Becker said. Although patients may not necessarily be able to pinpoint that they have an issue with memory or attention, "they just feel like they are in a fog and something is different." They might not feel as sharp or like they are as able to do their usual tasks, she said. Or it might seem like it takes more effort than usual to complete those tasks.
"Our patients feel like they're working twice as hard, cognitively or otherwise, for half as much," said Jackson, who is also the lead psychologist at Vanderbilt’s Critical Illness, Brain Dysfunction and Survivorship Center.
How severe are post-COVID cognitive symptoms?
Post-COVID cognitive issues can cause real issues in people's lives, Jackson said. He recounted stories of people taking medication multiple times a day because they'd forgotten they had already taken it, of people getting out of their car while it's still in drive and of a woman who mistakenly introduced herself to a close friend of 15 years as if they'd never met.
Without adequate treatment, people may have severe issues with their jobs or have to go on disability benefits, Jackson said.
But one thing that’s been puzzling to researchers is that the severity of a patient’s initial COVID-19 infection doesn’t seem to predict how severe their cognitive symptoms will be afterward.
Other viruses, such as HIV and Epstein-Barr virus, are known to cause cognitive issues in some patients, Becker said. “So it’s not new that we’re seeing this, but it is unusual (to see these symptoms in) such a young patient population and so many months after having had this infection,” she explained.
Researchers are still working out whether any underlying factors or other aspects of the pandemic might make it more likely for some people to develop symptoms like these. For one thing, we do know that mental health issues — particularly depression and anxiety — can contribute to cognitive dysfunction, Jackson said.
Of course, the chronic stress of the pandemic exacerbated or triggered mental health issues in many people. So Becker's team is currently working on a study that compares people who did and didn't get COVID-19 during the same time period to help tease out the specific cognitive effects of the virus on its own.
Apart from that, "the other risk factors for having cognitive impairments still apply," Becker said. So, having underlying conditions (like heart disease, hypertension or diabetes) as well as poor diet and a sedentary lifestyle can all contribute to your overall risk for cognitive issues due to COVID-19 or other causes, she explained.
When should I talk to my doctor?
There's no hard rule here, but if you've been dealing with mild cognitive symptoms for a few months, Jackson said it's time to check in with your doctor.
But if your symptoms are noticeably impacting your life, you shouldn't wait to speak to a medical professional. Those impacts might show up as new difficulties keeping track of tasks at work, forgetting to take medication, trouble managing finances or issues while driving, Jackson said. "Those sorts of things we see a lot, and that's really why we worry about cognitive function."
At first, your doctor might say it's too early to know if your symptoms are due to COVID-19 and ask you to keep an eye on things for a few months, Becker said. "But I think that a lot of doctors who do their due diligence will say, 'Let's do some blood work. Let's try to figure out what else might be going on.'"
If blood work and screening tests rule out other possible causes, your doctor may recommend you speak to a neuropsychologist for a thorough evaluation, Becker added.
What kind of treatments are available?
If your cognitive symptoms are due to the lingering effects of COVID-19, both Becker and Jackson recommend asking your doctor about cognitive rehabilitation, a set of treatment options often used to help patients after traumatic brain injuries or to help with issues like "chemo brain."
Cognitive rehabilitation won't necessarily cure your post-COVID issues, but "you're going to learn strategies and work-around solutions to minimize the impact of your cognitive impairment," Jackson said. He also recommends people pursue computerized cognitive training on their own. And he said that puzzle games like Wordle and sudoku, while certainly not cures, can "promote brain health and be helpful to people with long COVID."
It's not clear yet how long these cognitive deficits typically last, Becker said, adding that longer-term studies are sorely needed. In a study published this past October in JAMA Network Open, Becker and her colleagues found that many patients (including those who weren't hospitalized) still had issues with things like memory and processing speed more than seven months after their diagnoses. So although these symptoms do seem to improve within a year for a small number of patients, "about a year after COVID, we're still seeing a large subset of people who are complaining of cognitive deficits," she said.
With so much unknown about these persistent COVID effects, it might feel like a hard road to get diagnosed and treated. But Jackson shared an optimistic message: "We see people consistently getting better. We see people consistently improving cognitively," he said. "That takes time and there's no guarantee. But there are reasons to be hopeful."