A recent study published in eBioMedicine has found that individuals experiencing neurocognitive symptoms after COVID-19 infection, known as Long COVID, show a significant increase in blood plasma levels of the tau protein. Tau is commonly associated with neurodegenerative diseases and is often present in high amounts in Alzheimer's patients.
Researchers at the Stony Brook World Trade Center (WTC) Health and Wellness Program conducted the study on 227 WTC responders who developed neurological post-acute sequelae of COVID (N-PASC). The team compared blood samples taken before and after COVID-19 infection, measuring phosphorylated tau (pTau-181), a form linked to dementia.
The results showed a 59 percent rise in pTau-181 among those with N-PASC following their infections. In contrast, a control group of 227 WTC responders—who either did not contract COVID-19 or had no Long COVID symptoms—did not display such increases.
"For those with N-PASC who had neurocognitive symptoms for more than 1.5 years, the tau level increases were worse. This finding, the authors write, 'might portend worsened cognitive functioning as individuals age.'"
"We measured tau at an average of 2.2 years after COVID-19 infection, and our measurements taken ranged from six months to four years," said Xiaohua Yang, First Author and Senior Research Program Manager at the Stony Brook WTC Health and Wellness Program. "This sampling timeframe represents a true long-term post-acute sequela of COVID-19."
The researchers emphasized that further studies are needed to determine if higher plasma tau levels are directly related to cognitive decline or neurodegenerative disease risk. "One important step is to validate our study results using neuroimaging tools to see if tau plasma level increases also represent increased levels in the participants' brains," explained Clouston.
The authors also noted that because all participants were WTC responders with unique environmental exposures, their findings may not apply broadly to the general population.
"The long-term impact of COVID-19 may be consequential years after the infection and give rise to long-term illnesses including neurocognitive problems similar to what is seen in Alzheimer's disease," said Senior Author Benjamin J. Luft, MD, Director of the WTC Health and Wellness Program.
"This is one of the first studies to show that a virus may contribute to the development of abnormal tau production over time," he added. "This has important implications for our understanding of the biological factors involved in the development of neurodegenerative disease. On a practical level, it has important implications for the development of effective vaccines and therapies to prevent an acute infection before it can embed itself in people and cause long-term disease."
Funding for this research was provided by grants from both the Centers for Disease Control and Prevention's National Institute for Occupational Safety and Health and the National Institutes of Health's National Institute on Aging.
