A sweeping international study of more than 3,100 long COVID patients has uncovered a striking global divide in brain-related symptoms.
A large international study led by Northwestern Medicine has found that people with long COVID in the United States report much higher levels of brain fog, depression, and other cognitive problems than patients in countries such as India and Nigeria.
Researchers stress that this does not necessarily mean the illness is more severe in the U.S. Instead, the heavier symptom burden reported by American patients may reflect lower stigma around mental health and better access to neurological and psychological care.
First Cross Continental Study of Neurological Effects
This is the first study to directly compare long COVID neurological symptoms across multiple continents. Scientists followed more than 3,100 adults receiving care for long COVID at academic medical centers in Chicago; Medellín, Colombia; Lagos, Nigeria; and Jaipur, India.
Most participants were not hospitalized during their initial COVID infections. Among these patients, 86% in the U.S. reported brain fog. That compares with 63% in Nigeria, 62% in Colombia, and just 15% in India.
A similar pattern appeared for emotional distress. Nearly 75% of non-hospitalized patients in the U.S. said they experienced depression or anxiety. In Colombia, about 40% reported those symptoms, while fewer than 20% did so in Nigeria and India.
“It is culturally accepted in the U.S. and Colombia to talk about mental health and cognitive issues, whereas that is not the case in Nigeria and India,” said Dr. Igor Koralnik, senior study author and chief of neuro-infectious disease and global neurology at Northwestern University Feinberg School of Medicine.
“Cultural denial of mood disorder symptoms as well as a combination of stigma, misperceptions, religiosity and belief systems, and lack of health literacy may contribute to biased reporting. This may be compounded by a dearth of mental health providers and perceived treatment options in those countries.”
The findings will be published Jan. 28 in Frontiers in Human Neuroscience.
Most Common Neurological Symptoms
Across all four countries, the most frequently reported neurological symptoms included brain fog, fatigue, myalgia (muscle pain), headache, dizziness, and sensory disturbances (such as numbness or tingling).
Sleep problems were also more common in the U.S. Nearly 60% of non-hospitalized American patients reported insomnia, compared with roughly one-third or fewer of patients in Colombia, Nigeria, and India.
When researchers analyzed the data statistically, they found that symptom patterns clustered by income level rather than geography. High- and upper-middle-income countries (U.S., Colombia) grouped together, while lower-middle-income countries (Nigeria, India) formed a separate cluster.
How Researchers Conducted the Study
The observational study enrolled adults with lingering neurological symptoms after COVID-19 infection between 2020 and 2025. Patients were recruited from four academic medical centers and included both those who had been hospitalized and those who had not.
Investigators used standardized tools to measure neurological function, cognitive performance, and quality of life at each location, allowing consistent comparisons across countries.
The Broader Impact of Long COVID
Long COVID affects millions of people worldwide. It refers to symptoms that continue for weeks or even years after an initial infection. Studies suggest that 10-30% of adults who contract COVID develop longer-term health problems, with cognitive and neurological issues among the most disruptive.
As the authors write, long COVID “affects young and middle-aged adults in their prime, causing significant detrimental impact on the workforce, productivity, and innovation all over the world.”
In this study, patients in the U.S. consistently described the greatest neurological and psychological burden, which “affected their quality of life and ability to work,” according to Koralnik, who also serves as co-director of the Comprehensive COVID Center at Northwestern Medicine and leads the program for global neurology at the Havey Institute for Global Health at Feinberg.
What Comes Next
The researchers say their results highlight the need for screening tools and diagnostic approaches that take cultural differences into account. They also emphasize the importance of healthcare systems that can provide long-term monitoring and treatment for people with long COVID.
Building on these findings, Koralnik and international collaborators are now testing cognitive rehabilitation programs for long COVID brain fog in Colombia and Nigeria. These programs use the same treatment protocols developed for patients at the Shirley Ryan AbilityLab in Chicago.
The study is titled “A cross-continental comparative analysis of the neurological manifestations of Long COVID.”
Reference: “A cross-continental comparative analysis of the neurological manifestations of Long COVID” by Millenia Jimenez, Melissa Lopez, Janet Miller, Njideka U. Okubadejo, Carolina Hurtado, Anurag Kumar Singh, Oluwadamilola O. Ojo, Diego F. Rojas-Gualdron, Iorhen Akase, Osigwe P. Agabi, Kamlesh Kumar, Balvir Singh Tomar, Deepak Nathiya, Rebecca Jules, Eric M. Liotta and Igor J. Koralnik, 31 December 2025, Frontiers in Human Neuroscience.
DOI: 10.3389/fnhum.2025.1760173
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1 Comment
I reckon I would need brain-fog to survive in Trumpistan.