If you’ve ever been jet-lagged or pulled an all-nighter before going straight into work or school, you probably know the feeling. Maybe you had a harder time focusing that day, were more irritable and forgetful than usual, or just felt mentally off.
Brain fog, a term used to describe feelings of mental fuzziness, affects everyone differently. And while there are many health conditions known to cause brain fog, Covid-19 seems to have a unique and serious impact on some people’s ability to think clearly.
Scientists are just beginning to understand how Covid affects the brain, but growing evidence shows that even mild to moderate coronavirus infections can cause brain damage and trigger problems with memory, concentration and executive functioning.
In most cases, this brain fog resolves naturally within a matter of weeks, but some people develop chronic brain fog that persists for months, and maybe even years. Because Covid is still relatively new, we don’t yet know how long that brain fog is capable of lasting.
Here’s what we know about Covid-related brain fog, and how to cope with it:
Why does Covid-19 cause brain fog?
There are many health conditions and infections known to cause brain fog. Sepsis causes inflammatory changes in the brain that affects cognitive function and attention, and brain fog is a telltale symptom of Lyme disease and cancer that’s being treated with chemotherapy (you may have heard of “chemo brain”). Even some people who contract influenza develop brain fog – something that’s been dubbed “flu brain.”
There’s something unique about the brain fog that comes with Covid, according to James Giordano, a professor of neurology and biochemistry at Georgetown University Medical Center. With most of these other conditions, brain fog typically resolves when the infection clears or the treatment stops. Covid, however, seems to cause a much more intense and sometimes long-lasting, widespread inflammatory effect – and the brain fog can persist for weeks or months on end.
The brain fog people experience with long Covid is most likely a result of direct and indirect inflammatory effects on the brain, Giordano says.
We now know that COvid can, in some cases, trigger a massive inflammatory response that can cause a lot of tissue damage throughout the body. Evidence also suggests the coronavirus can directly infect cells in and around the brain, creating an inflammatory response in the brain itself. Plus, even when the infection clears, the inflammatory responses in and around the brain can persist and cause issues with cognition, behaviour and functioning. There’s also a theory that the virus may continue to exist at very low levels in some patients and cause ongoing symptoms.
Earlier in the pandemic, researchers suspected that long Covid was mostly a consequence of severe infections, but a study published in the journal Nature this month found that even mild to moderate cases of Covid can damage the brain and cause cognitive decline.
“Now we are really seeing inflammatory changes in the brain, and those inflammatory changes disrupt the functional architecture of the way brain nodes and networks are operating to control certain aspects of cognition and behaviour,” Giordano says.
Brain fog varies from person to person
A Covid diagnosis does not mean you will definitely go on to experience brain fog. Many people will clear the infection and bounce back immediately. Some will gradually improve over time. In others, however, the brain fog persists — and occasionally, it can become chronic and debilitating.
“That’s one of the really fascinating things about this virus. Each body that it goes into, it can affect so differently,” says Dr. Mill Etienne, an associate professor of neurology and medicine at New York Medical College.
This makes it very hard to predict who will develop brain fog. Age seems to play a role, as older people are more at risk for experiencing cognitive issues after Covid, according to Giordano. But even some young, otherwise healthy people diagnosed with Covid have found themselves struggling with brain fog.
“You don’t have to have a severe case of Covid in order to have this long Covid syndrome,” Etienne says.
Giordano says the specific symptoms of brain fog also vary from person to person. Some people experience fatigue after the slightest level of physical or mental exertion.
“It’s not just that they feel tired; they literally feel like they can’t do this anymore — in other words, they have to stop doing anything and just kind of rest,” Giordano says.
Brain fog can also cause short-term memory problems and issues with multitasking. Certain people may find it more difficult to concentrate or stick with a task, and others will experience coordination problems or become emotionally labile. Sensory changes – like, most notably, sense of smell and taste – also fall under the umbrella of brain fog.
Etienne, who routinely treats long Covid patients who have brain fog, said he has seen high-functioning adults suddenly struggle with multitasking and concentration. In severe cases, the brain fog can cost them their livelihoods, he added.
“It’s not just that they feel tired; they literally feel like they can’t do this anymore — in other words, they have to stop doing anything and just kind of rest.”
- James Giordano, Georgetown University Medical Center
Here’s how to manage Covid-induced brain fog
Most of the time, the brain fog will clear up naturally over time, Etienne says. But there are people who were infected early on in the coronavirus pandemic who continue, two years later, to experience brain fog.
If you’ve been battling brain fog after Covid, try to acknowledge that you have it and recognise its impact on your daily functioning and quality of life, Giordano advises. Consult with a physician and be specific about what brain fog feels like to you. Doing so will help your doctor develop a tailored treatment plan that will help mitigate the specific effects you are experiencing. In certain instances, medications and anti-inflammatory drugs may be recommended.
Though it can be difficult for people experiencing more moderate to severe cognitive symptoms, try to stay physically active and keep your brain active with recuperative mental tasks called cognitive crunches (think: playing games or making notes, lists and reminders).
“If you don’t use it, you tend to lose it,” Giordano says.
Some infectious disease experts recommend following an anti-inflammatory diet. Avoid fried foods, food high in saturated fat, and added sugars that cause inflammation. The Mediterranean diet, for example, is rich in antioxidants, which are known to mitigate inflammatory effects in the brain and body, Giordano said.
Lastly, get adequate rest and stay hydrated. “People usually take those things for granted,” Giordano says, “but in this particular case, it’s rather important because both rest and hydration can be very recuperative to brain metabolism.”
Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit gov.uk/coronavirus and nhs.uk.