Blood Clots May Cause ‘Brain Fog’ After COVID

A study has found blood clots may be a cause of cognitive problems such as ‘brain fog’ in patients after COVID-19.

The study was supported by two NIHR Biomedical Research Centres: Leicester and Oxford Health. It was funded by MQ Mental Health Research and the Wolfson Foundation.

Researchers from the University of Oxford analysed blood tests from 1,837 people hospitalised with COVID-19. They were looking for potential ‘biomarkers’ associated with cognitive problems that the patients experienced later. The symptoms included serious and persistent problems with thinking, concentration and memory.

The researchers identified two separate profiles of biomarkers. The first was having a high level of a protein called fibrinogen. The second was a raised level of a protein fragment called D-dimer.

On the discovery of patients with high levels of the two proteins, Dr Max Taquet from the University of Oxford said: “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. 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.”