An image for illustrative purposes [123RF]
An image for illustrative purposes [123RF]

A new study has offered clues to the neurological mechanisms behind long COVID — the condition in which patients experience fatigue, sleep disorders, difficulty concentrating and other so-called "brain fog" symptoms for months after a COVID-19 infection.

The Korea Institute of Toxicology announced Wednesday that a joint research team led by Dr. Shin Won-ho of the institute and Dr. Kwon Young-chan of the Korea Research Institute of Chemical Technology found that the COVID-19 virus selectively suppresses the brain's orexin system and causes a prolonged decline in cortical neuron function.

Long COVID refers to a condition in which fatigue, cognitive impairment and sleep disorders persist for months or more after a COVID-19 infection, but the neurological mechanisms driving these symptoms have not been clearly established.

After tracking animal models infected with COVID-19 over an extended period, the research team confirmed that cortical neuron function continued to decline for as long as the virus remained in the brain.

This manifested as a reduction in NeuN — a marker of mature neurons — and the shrinkage of nerve cells.

At the same time, the team found a sharp drop in the production of orexin, a neurotransmitter that regulates sleep, wakefulness and energy balance.

These changes were not observed in animals infected with influenza A virus, another respiratory pathogen, confirming that the neurological effects are specific to COVID-19.

The same phenomenon was observed in COVID-19 variant strains.

When the research team administered orexin externally, NeuN expression — which had previously declined — increased without affecting viral replication.

The team said the finding suggests that impaired orexin function may be linked to the decline in neuron function seen after COVID-19 infection.

However, the team said the study does not prove orexin deficiency is a direct cause of long COVID, and added that it plans to conduct further research to establish a causal relationship.

"This research suggests that COVID-19 may disrupt the brain's orexin system and contribute to abnormal neuron function," Dr. Shin said. "It is significant in that it points to a new research direction for understanding the fatigue, sleep disorders and cognitive decline seen in long COVID patients."


husn7@heraldcorp.com