physician with patient
Igor Koralnik, MD, meets with a patient in the Northwestern Medicine Comprehensive COVID-19 Center.

January 2026

NEUROSCIENCES

STUDY FINDS BRAIN FOG FROM LONG COVID REPORTED MORE OFTEN IN U.S.

Patients with long COVID-19 in the U.S. report far higher rates of brain fog, depression and cognitive symptoms than patients in other countries. This finding was revealed by a large international study led by Northwestern Medicine; results were published in Frontiers in Human Neuroscience.

The authors note that higher reported symptom burden in the U.S. may reflect lower stigma and better access to neurological and mental health care, rather than more severe disease.

This observational study is the first cross-continental comparison of long COVID neurological manifestations. It tracked more than 3,100 adults with persistent neurological symptoms following COVID-19 infection between 2020 and 2025 in Chicago, Illinois; Medellín, Colombia; Lagos, Nigeria; and Jaipur, India.

Study Findings
  • Among patients who were not hospitalized during their COVID infections, 86% in the U.S. reported brain fog, compared with only 63% in Nigeria, 62% in Colombia and 15% in India.
  • Nearly 75% of nonhospitalized 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.
  • Brain fog, fatigue, myalgia, headache, dizziness and sensory disturbances were the most common neurological symptoms across all countries.
  • Insomnia was reported by nearly 60% of nonhospitalized 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.

​Study Takeaways
“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,” says Igor Koralnik, MD, senior study author. “This may be compounded by a dearth of mental health providers and perceived treatment options in those countries.”
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U.S. patients consistently reported the highest burden of neurological and psychological symptoms, which “affected their quality of life and ability to work,” says Dr. Koralnik, who also is the co-director of Northwestern Medicine Comprehensive COVID-19 Center and leader of Global Neurology at Robert J. Havey, MD Institute for Global Health.

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, Dr. 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.
Igor Koralnik, MD, the Archibald Church Professor of Neurology and chief of Neuro-infectious Disease and Global Neurology at Northwestern Medicine

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