At least 65 million peopleTrusted Source around the world have long COVID, a condition where they continue to experience COVID-19 symptoms for months after their symptoms originally start.

The most common symptoms of long COVID are fatigue, dizziness, mobility issues, sleep problems, cognitive impairment, and brain fog or inability to concentrate.

These types of lingering symptoms can have a profound impact on a person’s life. A study published in June 2023 found more than half of people with long COVID reported their work, home, social, and private lives were severely impacted by the symptoms, with fatigue being the main problem.

Scientists are still unsureTrusted Source as to why some people develop long COVID and its symptoms while others do not.

Now researchers from the Amsterdam University Medical Center are helping to provide some answers with their new study — recently published in the journal Nature CommunicationsTrusted Source — that found the fatigue experienced by those with long COVID has a physical cause.