- Long Covid patients showed a 10 per cent larger brain structure linked to immune response.
- Changes were tied to proteins associated with Alzheimer’s disease.
- Scientists say more long-term research is needed.
A new study suggests that long Covid and Alzheimer’s disease may share underlying biological mechanisms, raising fresh questions about the long-term impact of Covid-19 on the brain.
Researchers led by a team at New York University in the US found that people reporting long Covid symptoms had, on average, a 10 per cent larger choroid plexus. This is a network of blood vessels in the brain responsible for producing cerebrospinal fluid, which cushions the brain and helps clear waste.
The choroid plexus also plays a role in regulating immune responses, including inflammation. Problems with the brain’s waste clearance system have previously been linked to dementia, of which Alzheimer’s is the most common form.
The study, published in the journal Alzheimer’s and Dementia, examined 179 participants. Of these, 86 had neurological symptoms linked to long Covid, 67 had recovered fully from COVID-19 without lasting symptoms, and 26 had never had the infection. All underwent MRI scans.
According to the researchers, those with long Covid not only showed an enlarged choroid plexus but also reduced blood flow in the same region. The team wrote in the study that long COVID patients show choroid plexus enlargement and reduced cerebral blood flow, and that these alterations are associated with Alzheimer’s-related symptoms and changes in blood biomarkers.
An increase in the size of this brain structure was linked to higher levels of certain blood proteins, including pTau217, which has been studied as a marker that rises as Alzheimer’s disease progresses. Elevated levels of glial fibrillary acidic protein, which can increase after brain injury, were also observed.
Patients with a larger choroid plexus scored on average 2 per cent lower on the Mini-Mental State Exam, a 30-point test used to assess memory and attention.
Yulin Ge, senior author of the study and professor of radiology at New York University’s school of medicine, reportedly said that long-term immune reactions following an initial COVID infection may cause swelling that damages a critical brain barrier in the choroid plexus. Physical, molecular and clinical evidence suggests that a larger choroid plexus may act as an early warning sign of future Alzheimer’s-like cognitive decline, he reportedly added.
Long Covid has often been associated with so-called brain fog, including difficulty concentrating and memory lapses.
Inflammation under scrutiny
The researchers suggested that the structural changes could reflect inflammation-driven vascular remodelling. In simple terms, the layers of cells lining the blood vessels may thicken in response to prolonged immune activation. This may be accompanied by stromal fibrosis, a build-up of scar-like tissue that can further restrict blood flow.
Reduced blood perfusion in the choroid plexus could limit the production of cerebrospinal fluid, potentially leading to waste build-up in the brain and weakening the blood-cerebrospinal fluid barrier.
Thomas Wisniewski, senior author and professor of neurology at New York University’s school of medicine, reportedly said the next step is to follow patients over time to see whether these brain changes can predict who develops long-term cognitive problems. A larger and longer-term study will be needed to determine whether the observed alterations are a cause or a consequence of neurological symptoms, he reportedly said.
The findings come amid broader research into COVID-19’s lasting health effects. A separate study published in the European Heart Journal in August 2025 suggested that a COVID-19 infection may age blood vessels by up to five years, with women potentially more affected than men.
While the latest research does not claim that long Covid directly causes Alzheimer’s disease, it adds to growing evidence that the virus may leave a more lasting imprint on the brain than first thought.
