- Long Covid patients showed 10% larger choroid plexus in the brain than others
- Choroid plexus regulates brain immune response and waste clearance
- Enlarged choroid plexus linked to Alzheimer's markers and cognitive decline
A new study has suggested that long Covid, which refers to 'SARS-CoV-2' symptoms that persist despite having healed from the initial infection, and Alzheimer's disease may share processes by which one is affected. Researchers, led by those from the US' New York University, found that people reporting long Covid symptoms had a 10 per cent larger choroid plexus (ChP) -- a network of blood vessels lined by cells that produce cerebrospinal fluid, which cushions the brain. The ChP regulates immune system responses, such as inflammation and waste clearance in the brain, they said.
Studies have shown that problems with the brain's waste clearance can result in dementia, of which Alzheimer's disease is the common form.
Studies have also shown that the COVID-19 virus, or 'SARS-CoV-2', can damage the cells lining the blood vessels forming the choroid plexus, the researchers said.
"Long coronavirus disease (COVID) patients show choroid plexus enlargement and reduced cerebral blood flow. ChP alterations are associated with Alzheimer's disease-related symptoms and plasma biomarker changes," the authors wrote in the study published in the journal Alzheimer's and Dementia.
An increase in the size of the choroid plexus was related to levels of blood proteins, such as 'pTau217', previously studied to increase as Alzheimer's disease worsens, the team said.
They also found blood proteins such as glial fibrillary acidic protein, which have been shown to increase in response to brain injury.
Further, the team found that patients with a larger choroid plexus performed on average two per cent worse on the Mini-Mental State Exam -- a standard 30-point screening test which records changes in memory and attention.
"Our work suggests that long-term immune reactions caused in some cases after an initial COVID infection may come with swelling that damages a critical brain barrier in the choroid plexus," said senior author Yulin Ge, a professor in the department of radiology at New York University's school of medicine.
"Physical, molecular, and clinical evidence suggests that a larger (ChP) may be an early warning sign of future Alzheimer 's-like cognitive decline," Ge said.
Symptoms of long Covid have often been said to include 'brain fog' and difficulties in focusing and cognition.
The study looked at 179 participants -- 86 patients with neurological symptoms of long COVID, 67 people who had fully recovered from COVID-19 without lasting symptoms, and 26 individuals who never had COVID-19 -- who underwent a magnetic resonance imaging (MRI) scan of their brains.
Structural changes seen in the choroid plexus network of blood vessels among long COVID patients both expanded the overall volume and reduced flow through its blood vessels, the researchers said.
While the mechanisms behind the result are not yet confirmed, the team suggested that the changes reflect inflammation-driven ChP "vascular remodelling", in which layers of cells lining blood vessels thicken in response to long-term activation by immune cells and signals.
The inflammation is accompanied by surrounding stromal fibrosis -- a buildup of scar-like tissue that further hinders blood flow, the researchers said.
An impaired blood perfusion in the ChP may reduce cerebrospinal fluid production, lead to waste buildup, and compromise the integrity of the blood-cerebrospinal fluid barrier, the authors said.
"Our next step is to follow these patients over time to see if the brain changes we identified can predict who will develop long-term cognitive issues," said senior author Thomas Wisniewski, professor in the department of neurology at New York University's school of medicine.
"A larger, long-term study will be needed to clarify whether these (ChP) alterations are a cause or a consequence of the neurological symptoms, which promises to better focus treatment design efforts," Wisniewski said.
A study, published in the European Heart Journal in August 2025, suggested that a COVID-19 infection may age one's blood vessels by up to five years, with women affected more compared to men.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
