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The most common symptoms of COVID-19 include fever, cough, shortness of breath, and fatigue. However, neurological symptoms — those that affect your brain and nervous system — are reported in up to 25 percent of people who develop COVID-19.

Lingering “brain fog” is one neurological symptom that people with COVID-19 commonly report. In some cases, brain fog, or cognitive impairment, can last many months after the disease has passed.

In this article, we’ll take a closer look at why COVID-19 causes brain fog in some people, how common it is, and when to get help for these neurological issues.

Brain fog isn’t a medical diagnosis. Instead, it’s a general term used to describe the feeling of being mentally slow, fuzzy, or spaced out.

Symptoms of brain fog can include:

Most people experience periods of brain fog occasionally. You’ve likely felt mentally sluggish after a night of poor sleep or when you’ve been under a lot of stress.

But some people who’ve had COVID-19 report brain fog that lasts weeks or even months after their other symptoms — like cough, fatigue, or fever —have gone away.

Researchers are still investigating the potential cause of brain fog in people who’ve had COVID-19. It’s thought that both physiological and psychological factors may play a role.

The new coronavirus that causes COVID-19, known as SARS-CoV-2, is thought to typically spread through close contact with someone who has the infection. Respiratory droplets from that person can enter your body through your nose, mouth, or eyes.

Once in your system, the coronavirus enters cells through an enzyme called angiotensin-converting enzyme 2 (ACE2) receptor. The virus is neuro-invasive, meaning that it can enter your brain tissue.

Numerous case studies have found that some people who’ve had COVID-19 develop complications such as altered consciousness or encephalopathy. Encephalopathy is a general term that refers to damage or disease of your brain.

A study from January 2021 found increased levels of inflammatory cytokines in the fluid surrounding the brains of people weeks after their COVID-19 infection. Cytokines are molecules produced by your immune system that encourage inflammation.

Inflammation in your brain hinders the ability of your neurons to communicate with each other. This may be one of the factors that contributes to brain fog.

Researchers have also identified microstructural changes in the hippocampus and other areas of the brain after COVID-19. They believe that these changes may also contribute to cognitive impairments.

Other factors that may contribute to brain fog

As mentioned above, inflammation in and around your brain may contribute to brain fog. However, there are other ways that COVID-19 may indirectly lead to brain fog as well.

Some possible contributing factors include:

Researchers are still working to understand how common brain fog is in people who’ve had COVID-19.

One recent analysis showed that between 7.5 to 31 percent of people experience an altered mental state as a symptom of COVID-19. However, this estimation was based on small studies and may not be applicable to a larger population.

Another recent study reports that neurological symptoms could be more widespread than originally thought and may occur in up to 69 percent of people who’ve had severe illness with COVID-19.

At this time, it’s not clear why some people develop brain fog and others don’t. People with severe cases of COVID-19 seem to be at a higher risk for developing neurological symptoms than people with mild disease.

Severe brain-related complications such as delirium, seizure, and inflammation of the brain and surrounding tissues are most common in critically ill patients.

It’s still not clear how long brain fog typically lasts after COVID-19. Some people report brain fog that lingers for weeks or months after their respiratory symptoms have gone away.

A study published in December 2020 found that about 28 percent of people had lingering concentration problems more than 100 days after hospital admission for COVID-19.

In another study, researchers found that out of a group of 60 patients who’d recovered from COVID-19, 55 percent still had neurological symptoms 3 months after their illness. These symptoms included:

  • mood changes
  • fatigue
  • headaches
  • visual disturbances

As of now, the best treatment for brain fog caused by COVID-19 is to adopt healthy habits. The following tips may help boost your mental function if you’re dealing with ongoing brain fog.

  • Get plenty of sleep. Getting good quality sleep can help your body repair and recover.
  • Get regular exercise. Physical activity isn’t only beneficial to your heart and lungs, it’s also a great way to boost your brain function.
  • Eat well. Try to eat a well-balanced, healthy diet to give your body the nourishment it needs to return to good health.
  • Avoid tobacco and alcohol. Staying away from tobacco products and alcohol can help minimize inflammation in your brain.
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Researchers are continuing to look at the potential benefit of steroids for reducing inflammation of the brain that may contribute to cognitive changes.

It’s a good idea to see your doctor if your mental symptoms are severe enough that they interfere with your daily life or if they don’t improve after a couple of weeks.

If you have COVID-19, it’s important that you seek immediate medical attention if you have any of the following symptoms:

Some people with COVID-19 report having brain fog for weeks or months after their respiratory symptoms pass. It’s thought that a combination of physiological changes in the brain and psychological factors may contribute to this condition.

Researchers are still trying to understand why some people develop neurological symptoms of COVID-19 and others don’t. If you’ve had COVID-19 and have lingering cognitive issues that affect your ability to think clearly, be sure to follow up with your doctor.