Long COVID, Brain Health, and Cognitive Decline: What the Science Says

When the world first heard of COVID-19, attention centered on its impact on the lungs. But now, a half decade later, researchers are discovering that the virus may leave a deeper, longer-lasting imprint on the brain. Recent studies suggest that COVID-19 can affect memory, cognition, and might even increase the risk for neurodegenerative disease. What’s clear so far is that much remains unknown. Neurologists are working to separate speculation from science.

How Long COVID impacts the brain

One of the clearest patterns emerging is the connection between COVID-19 and cognitive difficulties — sometimes referred to as, simply, “brain fog.” 

People living with Long COVID often report memory problems, concentration issues, and mental fatigue at significantly higher rates than those who were never infected. Studies estimate these patients are anywhere from a third to three times more likely to experience cognitive impairment, with a more severe initial infection leading to more deficits. Even those with relatively mild cases aren’t immune: research has found subtle but measurable changes in thinking skills, including a small but real drop in IQ compared with people who never had the virus.

Rutgers neurologist Dr. William T. Hu told Being Patient last year: “What we’re able to see, and what others have reported, is that the virus is seen in the blood vessels in the brain. They likely enter the brain in small amounts and hide out in the brain cells or the inflammatory cells.”

Imaging and biomarker studies add weight to these observations. Brain scans have shown shrinkage in areas crucial for memory, such as the hippocampus, and decreased connectivity between the amygdala and regions that regulate emotion and cognition.

Changes in brain signalling might be involved too.

In October 2025, Japanese researchers published a study in the journal Brain Communications using brain imaging to compare 30 people with long COVID brain fog to 80 healthy individuals. The people with brain fog had higher numbers of AMPA receptors, which are proteins involved in brain signalling, throughout the brain. 

When activated by a signaling molecule called glutamate, AMPA receptors make brain cells fire off electrical signals. Too much stimulation causes damage. 

Researchers aren’t sure yet whether these higher levels result from long COVID or the brain’s way of compensating for other problems. If other groups of researchers replicate these findings in larger groups of long COVID patients, it could pave the way for trials testing AMPA receptor-modulating drugs to alleviate brain fog.

 

The role of inflammation in post-COVID brain health

Underlying these changes, inflammation seems to be a key driver. COVID infection can unleash a storm of immune activity, and it’s this overactive immune response — rather than the virus directly invading brain cells — that researchers believe may damage neurons or interfere with normal brain function.

“With COVID, the difference there is that you have this massive inflammatory response. It’s so overactive and the body can’t handle it,” neuroscientist and Biohack Your Brain author Kristen Willeumier told Being Patient.“It absolutely could accelerate the symptoms of people who have dementia because a lot of these diseases of aging are chronic inflammatory diseases. COVID on top of it is like the double hit, which is why we really want to make sure the older populations are protected,” In many ways, COVID-19 is offering scientists a window into how inflammation in the body can ripple into the brain.

COVID-19 and Alzheimer’s risk

Despite these red flags, many questions remain unanswered. Does COVID directly cause Alzheimer’s, or does it simply speed up the course of disease in people who were already vulnerable? Are the brain changes seen on scans permanent, or can they reverse over time as the body heals? For now, data are mixed, and researchers caution against assuming the worst.

There is also little clarity on the long-term effects of reinfections and new variants. Some evidence suggests repeat infections could compound risk, but scientists are still collecting enough data to know for sure. Similarly, the role of vaccines in protecting against cognitive consequences remains under study. Age, education, pre-existing conditions, and genetics likely all play a role in determining who experiences the most severe cognitive impacts, but those factors aren’t fully mapped out yet.

Living with Long COVID

For people worried about brain health after COVID, experts recommend practical steps. Preventing reinfection remains critical, and symptoms of brain fog or memory loss should be taken seriously. 

“For people who have long COVID, the key thing is to avoid getting [COVID] again. That’s what we tell all our patients and research participants,” Hu said. 

Hu also advises pacing — “reduce the amount of what you expect to do on a daily basis … so that you give your body a chance to recover in the long run.” 

According to neurologist Robert Wilson, symptoms like brain fog or fatigue are often “non-specific… They can’t be localized,” and that makes them difficult for medical providers to pin down. 

“These symptoms can be very confusing,” he told Being Patient, “not confusing to the person going through them — they want a diagnosis, they know what they’re going through — but they’re confusing often to medical providers.”

Seeking medical advice — especially from neurologists — can help with monitoring and, in some cases, early interventions. 

“There are a lot of reasons to have memory issues that are not Alzheimer’s” explained Banner Institute neurologist Dr. Marwan Sabbagh in a conversation about pushing for answers in the face of cognitive concerns. “The patient should be asking about the new blood tests, the new scans, the new technologies … They should not be letting doctors dismiss their complaints.”

Lifestyle changes that support brain health, like exercise (the type and intensity might depend on the specific effects of Long Covid), quality sleep, stress management, and a balanced diet, may also help buffer the brain against inflammation and accelerate recovery. None of these are guaranteed fixes, but they align with what’s known about resilience in the face of stress and illness.

Science-backed strategies for coping with COVID brain fog

Mild cognitive impairment can be caused by a number of treatable conditions, from hormonal changes to sleep apnea, thyroid issues to anxiety. In these cases, treating such underlying conditions can reverse MCI. A specialist can help you establish there is no other underlying, treatable cause for cognitive issues. Check that first, experts say. 

And if Long COVID seems to indeed be the culprit for memory issues or general fogginess, neurologists outline several practical approaches to managing post-COVID brain fog:

• Get evaluated: Dr. Majid Fotuhi recommends a cognitive evaluation to measure your mental function compared with age-matched norms. “Anything under the 10th percentile warrants a trip to the neurologist.”
• Stay hydrated: As Willeumier explained, “If somebody has brain fog, I’ll have them drink at least half their body’s weight in ounces of water … Something as simple as making sure you get the appropriate amount of water can improve your mental and physical state.”
• Take symptoms seriously: Fotuhi told Being Patient, “People need to treat brain fog as they would a urinary tract infection or a rash. If you have a skin rash, you don’t just sit there and look at it. You have to do something about it.”

These strategies don’t guarantee recovery for everyone, but they reflect what neurologists have found helpful for many people living with post-COVID cognitive issues.

As the research accumulates, one thing is clear: COVID-19’s reach extends beyond the lungs, and for some, the brain may be its most lasting battleground. The research to date points to real risks for cognitive decline and long-term neurodegeneration, but it also highlights the resilience and adaptability of the brain.

Scientists are still learning how much damage can be healed, who is most at risk, and what interventions might make the difference. Until then, awareness and prevention remain powerful tools. 

COVID and brain health: Frequently asked questions

Can COVID-19 cause brain fog?

Yes, many people with Long COVID report ongoing cognitive issues, often referred to as “brain fog.” This can include difficulties with memory, concentration, and mental clarity. Studies show that individuals who have had COVID-19—even mild cases—are more likely to experience these cognitive impairments compared to those who have never been infected. For some, these issues can persist for months after recovery from the virus, contributing to a decreased quality of life.

Does COVID-19 increase the risk of Alzheimer’s or dementia?

While it’s still too early to draw definitive conclusions, studies have shown that some people who recover from COVID develop biomarkers associated with Alzheimer’s, such as elevated tau proteins and neuroinflammation. The virus appears to accelerate neurodegeneration in certain individuals, particularly those who were already at risk due to age or pre-existing conditions. However, more research is needed to understand if COVID directly causes Alzheimer’s or merely speeds up the progression of existing risks.

Are COVID-related brain changes permanent?

At this stage, we don’t fully know if the brain changes caused by COVID-19 are permanent. Some patients have regained lost cognitive function over time, while others continue to struggle with long-lasting effects. Brain imaging studies have shown changes such as shrinkage in the hippocampus, a key memory region, and altered brain connectivity. These changes may reverse as the brain heals, but the timeline for recovery varies. Ongoing research will help clarify whether these changes are temporary or if they signal a more lasting impact.

How does COVID affect the brain?

COVID-19 impacts the brain primarily through inflammation. When the body fights the virus, the immune system can trigger an overactive response that leads to neuroinflammation. This inflammation may damage brain cells, impair neural connections, and disrupt normal brain functions. Some researchers believe this overactive immune response, rather than the virus itself, is largely responsible for the cognitive issues seen in Long COVID patients. Elevated levels of inflammatory markers in the blood and cerebrospinal fluid suggest that inflammation may play a key role in these long-term neurological effects.

“What can I do to protect my brain after COVID?”

To protect your brain after COVID-19, prevention is key. Minimizing reinfections by following health guidelines and staying updated on vaccinations can help reduce the risk of cognitive issues. If you’re experiencing memory difficulties or brain fog, it’s important to consult a healthcare professional who can assess your symptoms and guide you toward appropriate treatment. In addition, adopting brain-healthy habits like regular physical exercise, adequate sleep, a nutritious diet, and stress management can support cognitive recovery and help mitigate further damage caused by inflammation.

UPDATED: October 10, 2025, 12:01 A.M. – This Sept. 29, 2025 article was updated to include research from an October 2025 study suggesting that changes in brain signaling may contribute to long COVID–related brain fog.