Scientists have revealed that blood clots could be the cause of ongoing cognitive problems in patients with Covid.
Researchers at the University of Oxford examined blood tests from 1,837 people who had been hospitalised with the virus to find potential biomarkers associated with subsequent cognitive problems, including serious and persistent problems with concentration and memory.
Biomarkers are defined by the Institute of Cancer Research as a biological measure that can be used to detect or monitor a feature of a disease.
In the Oxford study, scientists identified two separate biomarkers in patients with Covid: a protein called fibrinogen and another protein fragment called D-dimer. Both are involved in blood clotting.
Participants’ memory was also assessed at six and 12 months after hospitalisation using both a formal test and by asking them their own subjective view about memory.
A participant in the study said: “Since my illness I have been plagued by brain fog, concentration-induced fatigue, poor vocabulary, poor memory. I am unable to process the amount and scale of work that I would previously have done ‘stood on my head’.”
Dr Max Taquet, of the department of psychiatry at the University of Oxford, said: “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.
“The ultimate goal is to be able to prevent and reverse the cognitive problems seen in some people after COVID-19 infection. Although our results are a significant advance in understanding the basis of these symptoms, more research is needed into the causes and effects before we propose and test interventions.”
Professor Paul Harrison, from the University of Oxford who supervised the study, said: “Identifying predictors and possible mechanisms is a key step in understanding post-COVID brain fog. This study provides some significant clues.”
The study was funded by MQ Mental Health Research and the Wolfson Foundation, with the support of the National Institute for Health and Care Research (NIHR) Biomedical Research Centres in Leicester and Oxford Health.
