Brain fog is one of the most common symptoms of long COVID. People who experience it often have trouble concentrating, remembering things, making decisions, or thinking quickly. It can make everyday life difficult, as tasks at work, school, or even at home may feel overwhelming, and personal relationships may also be affected. Long COVID is a condition where symptoms last for weeks, months, or even years after a COVID-19 infection, even if the infection itself was mild. The condition has affected millions of people worldwide.
While many may expect that brain fog is equally common everywhere, a new international study shows that this is not the case. Researchers from Northwestern Medicine studied over 3,100 adults with long COVID in four countries: the U.S., Colombia, Nigeria, and India. This was the first study to compare neurological symptoms of long COVID across different continents. The team focused on symptoms such as brain fog, long-lasting fatigue, and depression. They wanted to understand how often these problems appear in different parts of the world. The findings were unexpected.
Rates of brain fog varied widely between countries. In the United States, the numbers were especially high. Among patients who did not receive hospitalisation during their COVID infection, 86% reported experiencing brain fog. In contrast, only 63% of patients in Nigeria, 62% in Colombia, and just 15% in India said they experienced the symptom. Psychological issues showed a similar pattern. About 75% of U.S. patients reported anxiety or depression, compared with 40% in Colombia and less than 20% in Nigeria and India.
Dr Igor Koralnik, the senior author of the study, explained that these differences do not necessarily mean that people in the U.S. are sicker. “In the U.S. and Colombia, it’s culturally normal to talk about mental health and brain issues,” he said. “But in Nigeria and India, stigma, cultural beliefs, religion, and lack of knowledge about mental health may stop people from reporting these symptoms.
There are also fewer doctors and treatment options available.” The study also found that the most common neurological symptoms across all countries were brain fog, fatigue, muscle pain, headache, dizziness, and numbness or tingling. Insomnia was common in the U.S., affecting nearly 60% of non-hospitalised patients, but it was reported by about one-third or fewer patients in other countries.
Researchers noticed a clear pattern: countries with higher income, like the U.S. and Colombia, had higher reported symptom rates, while lower-middle-income countries like Nigeria and India reported fewer symptoms. Healthcare access, cultural attitudes, and reporting habits may have a greater influence than the severity of the disease. The study encompassed adults experiencing persistent neurological issues following COVID-19 infection from 2020 to 2025. Both hospitalised and nonhospitalized patients were studied, and researchers used standardised tools to measure cognitive problems, mental health, and quality of life at each medical center.
Long COVID affects people of all ages but is particularly common among young and middle-aged adults. The symptoms can significantly impact work, productivity, and daily life. As Dr Koralnik noted, these ongoing health problems “affect people in their prime, harming not just their quality of life but also innovation and workforce productivity around the world.” The study draws attention to the requirement for healthcare systems to consider cultural differences when diagnosing and treating long COVID. Screening tools and treatments should be adapted to local cultures and resources.
The research team is now testing new brain training programs. Colombia and Nigeria are testing these programmes. They are based on methods already used with patients in Chicago. The goal is to reduce brain fog and help patients regain their daily functioning. In summary, brain fog is a common and serious symptom of long COVID. However, people report it more in some countries than others. Culture plays a role. Access to healthcare matters. Awareness of mental health also makes a difference. Understanding these differences is essential. It helps doctors give better care and also supports people with long-term COVID around the world.
