As scientists try to get a better idea of what causes long COVID symptoms, researchers think blood clotting proteins could be what causes the persistent brain fog many COVID-19 long haulers complain of.
The University of Oxford found the high levels of proteins fibrinogen and D-dimer helped predict whether patients would experience brain fog while battling long COVID.
Their study included 1,837 adults hospitalized with COVID-19. The researchers said the presence of the two proteins at the time of hospitalization helped predict the patients' cognitive outcomes six and 12 months after hospitalization.
"Both fibrinogen and D-dimer are involved in blood clotting, and so the results support the hypothesis that blood clots are a cause of post-COVID cognitive problems," said Dr Max Taquet, a senior research fellow and lead author of the study. "Fibrinogen may be directly acting on the brain and its blood vessels, whereas D-dimer often reflects blood clots in the lungs and the problems in the brain might be due to lack of oxygen. In line with this possibility, people who had high levels of D-dimer were not only at a higher risk of brain fog, but also at a higher risk of respiratory problems."
Long COVID symptoms can continue for months and even years, experts said.
The Centers for Disease Control and Prevention lists 19 different ailments as common long COVID symptoms. The symptoms can range from prolonged coughs and fevers, symptoms common in primary COVID infections, to neurologic and cardiovascular symptoms.
Many people with long COVID complain of persistent fatigue, drowsiness and brain fog.
Researchers said their goal is to prevent and reverse the cognitive problems seen in some people after COVID-19 infection.
"Identifying predictors and possible mechanisms is a key step in understanding post-COVID brain fog. This study provides some significant clues," said Oxford professor Paul Harrison.
Justin Boggs
