Since the beginning of the COVID-19 pandemic, researchers have worked at lightning speed to develop tests, vaccines, and treatments. Despite all of these breakthroughs, there is still a lot we do not know about this disease, and particularly about its long-term effects, known as long COVID.

Fatigue is the most prevalent symptom of long COVID, but many people report ongoing neurological and psychological symptoms. The effects it has on the brain are some of the biggest unknowns and are attracting a lot of interest from researchers.

The Beginning of Long COVID

Long COVID was largely defined by the people experiencing it coming forward about their symptoms on social media. At the start of the pandemic, people were not warned of the possibilities of long COVID because so much was unknown about the novel virus.

As the first wave recovered, many previously healthy people described symptoms that persisted or appeared weeks after infection. After fatigue, neurological symptoms such as confusion, poor concentration and memory, and brain fog were common.

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One study indicates that the long-term cognitive problems in long COVID may be due to inflammation as measured by CRP. The liver makes CRP or c-reaction protein in response to inflammation.

Previous studies have linked high CRP and inflammation to long-term cognitive decline and changes in memory, attention, self-control, and verbal fluency, but more research is needed about how CRP relates to long COVID.

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Silent Strokes

Strokes are common in people recovered from COVID, particularly those over 70.

Silent strokes may also occur, and these typically affect the white matter that facilitates communication between parts of the brain and plays a role in attention and other cognitive functions. If someone with COVID experiences a silent stroke, it can affect their brain significantly, and they may not even realize that anything happened.

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Alzheimer's Disease

Some studies suggest that COVID survivors are at greater risk for neurological diseases, particularly Alzheimer's. Researchers are unsure of how COVID causes this, but they suspect it may be due to inflammation, encephalitis, organ dysfunction, or changes in the vasculature in the brain.

They theorize that COVID either aggravates a pre-existing neurological condition or initiates a new one, but more research and surveillance of COVID survivors is needed.

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COVID in the Brain

COVID may also directly affect the brain. Researchers know that the virus affects the olfactory muscosa, the tissue at the top of the nasal cavity, because loss of smell is a common symptom of COVID. Some researchers speculate that the virus could travel into the brain through this tissue. The virus may also be able to pass through the blood-brain barrier due to the inflammation and instability that it causes in the body.

If COVID can invade the brain stem, long-term neurological symptoms are likely.

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Mental Health

Long COVID is also likely to take a significant toll on mental health. Little is known about long COVID, so there is a lot of uncertainty for people experiencing it and few concrete answers. These things combined with a possible loss of income, difficulty obtaining benefits, and general skepticism about long COVID can lead to feelings of isolation and depression.

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Problems Diagnosing Long COVID

Researchers have many theories about long COVID and the brain, but diagnosis is challenging. Doctors cannot confirm any causes of long-term neurological and psychiatric symptoms of COVID as the things suspected to cause it are not detectable in the brains of COVID survivors.

No laboratory tests or imaging studies can provide objective results, so diagnosis depends on the subjective reporting of the person experiencing symptoms. Doctors can rule out other things, but there is no way to confirm long COVID.

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Risk Factors for Long COVID

Studies show that some people are more prone to developing long COVID than others. Women are more than twice as likely to get it than men, and many people who experience long COVID symptoms already have existing autoimmune diseases, indicating a possible connection.

People with a history of depression, anxiety, or mood disorders were also more vulnerable to developing long COVID. Some research indicates that people who had multisystem disease are more likely to develop long COVID.

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Prevalence of Long COVID

Long COVID is an essential part of ongoing COVID treatment and research for many reasons, one being that it affects so many survivors. Research shows that 87 percent of people hospitalized with COVID have symptoms 60 days after the onset of the disease, and about 4.5 percent of people have mild symptoms that continue for more than eight weeks.

Other studies claim that as many as half of non-hospitalized COVID patients have at least one symptom that lasts an average of four months. When considering how many people COVID has infected worldwide, millions of people may be experiencing long COVID and its effects on the brain.

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Future Research

Diagnosing long COVID is complex, and researchers are attempting to develop more definitive diagnosis criteria. The National Institutes of Health have committed to researching long COVID.

Among other things, its goals are to determine the underlying cause of long-term symptoms, why some people get it and others do not, and whether a COVID infection can trigger changes in the body that lead to chronic heart or brain disorders.

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