Patients with long COVID-19 in the U.S. report far higher rates of brain fog, depression and cognitive symptoms than patients in countries such as India and Nigeria, according to a large international study led by Northwestern Medicine.
The authors note that higher reported symptom burden in the U.S. may reflect lower stigma and greater access to neurological and mental health care, rather than more severe disease.
The study, the first cross-continental comparison of long COVID neurological manifestations, tracked more than 3,100 adults with long COVID evaluated at academic medical centers in Chicago; Medellín, Colombia; Lagos, Nigeria; and Jaipur, India.
Among patients who were not hospitalized during their COVID infections (the majority in the study), 86% in the U.S. reported brain fog, compared with only 63% in Nigeria, 62% in Colombia and 15% in India. Rates of psychological distress showed a similar pattern: Nearly 75% of non-hospitalized patients in the U.S. reported symptoms of depression or anxiety, compared with only 40% in Colombia and fewer than 20% in Nigeria and India.
Culturally accepted
“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.
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“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 study will publish Jan. 28 in Frontiers in Human Neuroscience.
Additional key findings
- Brain fog, fatigue, myalgia (muscle pain), headache, dizziness and sensory disturbances (such as numbness or tingling) were the most common neurological symptoms across all countries.
- Insomnia was reported by nearly 60% of non-hospitalized U.S. patients, compared with roughly one-third or fewer of patients in Colombia, Nigeria and India.
- Statistical clustering showed clear separation between high- and upper-middle-income (U.S., Colombia) and lower-middle-income (Nigeria, India) countries.
The observational study enrolled adults with persistent neurological symptoms following COVID-19 infection between 2020 and 2025 across four academic medical centers. Researchers included both hospitalized and non-hospitalized patients and assessed symptoms using standardized neurological, cognitive and quality-of-life instruments available at each site.
Understanding long COVID
Long COVID affects millions of people worldwide and is characterized by symptoms persisting for weeks or even years after an acute COVID infection. Various studies estimate that 10-30% of adults infected with COVID develop long-term symptoms, with neurological and cognitive complaints among the most common and disabling.
As the authors note in the study, 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, U.S. patients consistently reported the highest burden of neurological and psychological symptoms, which “affected their quality of life and ability to work,” says Koralnik, who also is the co-director of the Comprehensive COVID Center at Northwestern Medicine and leader of the program for global neurology at the Havey Institute for Global Health at Feinberg.
Lessons and what comes next
The authors say the findings underscore the need for culturally sensitive screening tools and diagnostic approaches for long COVID, as well as healthcare systems equipped to support long-term follow-up and treatment.
Building on this work, Koralnik and his international collaborators are now studying cognitive rehabilitation treatments for long COVID brain fog in Colombia and Nigeria, using the same protocols developed for patients treated at the Shirley Ryan AbilityLab in Chicago.
The study is titled “A cross-continental comparative analysis of the neurological manifestations of Long COVID.”
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