An international study found that long-term COVID patients in the US report more brain fog and psychological symptoms than patients in lower-income countries. The researchers believe that this difference is due to culture and access to health care, not biology – suggesting that millions of people around the world may be struggling invisibly.
- Large study of more than 3,100 people is first to directly compare long-term brain symptoms of COVID across continents
- Brain fog was reported by 86% of non-hospitalized patients in the US compared to only 15% of patients in India.
- Long-term patterns of COVID symptoms were related to income level rather than geographic location, the researchers found
- The striking differences are likely due to culture and access to health care, rather than differences in the virus itself
The long-term brain symptoms of COVID vary significantly from country to country
People with long-term COVID in the United States report much higher rates of brain fog, depression and cognitive problems than patients in countries like India and Nigeria, according to a large international study led by Northwestern Medicine.
The researchers note that these differences do not necessarily mean that Americans are experiencing more severe disease. Instead, the higher symptom burden reported in the US may reflect better access to neurological and mental health care, along with lower stigma when discussing cognitive and emotional symptoms.
First Intercontinental Comparison of Long COVID Neurology
The research represents the first study to directly compare neurological symptoms of prolonged COVID across continents. Researchers followed more than 3,100 adults with long-term COVID who were evaluated at academic medical centers in Chicago; Medellin, Colombia; Lagos, Nigeria; and Jaipur, India.
Most participants were not hospitalized during their initial COVID infections. In this group, 86% of US patients reported experiencing brain fog. In comparison, brain fog was reported by 63% of patients in Nigeria, 62% in Colombia, and just 15% in India.
Mental health symptoms followed a similar pattern. Nearly 75% of US outpatients report depression or anxiety. In Colombia, this number dropped to around 40%, while less than 20% of patients in Nigeria and India reported similar problems.
Symptom reporting is shaped by cultural attitudes
“In the US and Colombia it is culturally accepted to talk about mental health and cognitive issues, whereas in Nigeria and India it is not,” said Dr. Igor Koralnik, lead study author and chief of neuroinfectious diseases and global neurology at Northwestern University Feinberg School of Medicine.
“Cultural denial of mood disorder symptoms, as well as a combination of stigma, misperception, religiosity and belief systems, and lack of health literacy may contribute to biased reporting. A lack of mental health providers and perceived treatment options in these countries may contribute to this.”
The study was published today (January 28) in Frontiers of Human Neuroscience.
Key neurological findings across all regions
In every country studied, the most commonly reported neurological symptoms included brain fog, fatigue, myalgia (muscle pain), headache, dizziness, and sensory disturbances (such as numbness or tingling).
Sleep problems also varied greatly. Almost 60% of non-hospitalized patients in the US reported insomnia, compared with about one-third or less of patients in Colombia, Nigeria, and India.
When the researchers statistically analyzed symptom patterns, they found a clear difference between high- and upper-middle-income countries such as the US and Colombia and lower-middle-income countries such as Nigeria and India.
How the study was conducted
The observational study included adults with persistent neurologic symptoms after infection with COVID-19 between 2020 and 2025. Participants were recruited from four academic medical centers and included inpatients and outpatients.
Symptoms were assessed using standardized neurological, cognitive, and quality-of-life assessments available at each site, allowing the researchers to compare results across regions.
Why COVID has remained a global problem for so long
Long COVID affects millions of people worldwide and is defined by symptoms that persist for weeks or even years after the initial infection with COVID. Estimates suggest that 10-30% of adults who contract COVID will develop permanent symptoms, with cognitive and neurological problems among the most disruptive.
As the authors write, the prolonged COVID “affects young and middle-aged adults in their prime, with a significant detrimental impact on the workforce, productivity and innovation around the world.”
In that study, patients in the U.S. consistently reported the greatest neurological and psychological burden that “impacted 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 directs the global neurology program at the Havey Institute for Global Health in Feinberg.
What the findings mean For the future
The researchers say their results highlight the importance of culturally sensitive screening tools and diagnostic approaches for the long run of COVID. They also point to the need for health care systems that can support long-term care and follow-up care.
Based on these findings, Koralnik and his international collaborators are now testing a cognitive rehabilitation treatment for long-term COVID brain fog in Colombia and Nigeria. These studies use the same treatment protocols developed for patients at the Shirley Ryan AbilityLab in Chicago.
The study is titled “Intercontinental Comparative Analysis of Neurological Manifestations of Long COVID.”
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