The development of blood clots during COVID-19 infection could be behind continued cognitive problems of some individuals, a new paper has suggested.
A team led by Dr Max Taquet and Prof Paul Harrison from the University of Oxford analysed blood tests from 1,837 people who had been hospitalised with COVID-19.
They found two potential biomarkers measured at admission associated with subsequent cognitive problems up to a year afterwards. The first was a high level of fibrinogen and the second was a raised level of the protein fragment D-dimer.
Writing in Nature Medicine, the authors say other aspects of the profiles suggest these biomarkers are likely to reflect blood clots.
Dr Taquet 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. 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 research participants are part of the UKRI funded PHOSP-COVID (Post-hospitalisation COVID-19) study, led by University of Leicester. Their memory was assessed at six and 12 months after hospitalisation using both a formal objective test, and by asking them their own subjective view about their memory.
Taquet M, Skorniewska Z, Hampshire A, Chalmers JD, Ho LP, Horsley A, Marks M, Poinasamy K, Raman B, Leavy OC, Richardson M, Elneima O, McAuley HJC, Shikotra A, Singapuri A, Sereno M, Saunders RM, Harris VC, Houchen-Wolloff L, Greening NJ, Mansoori P, Harrison EM, Docherty AB, Lone NI, Quint J, Sattar N, Brightling CE, Wain LV, Evans RE, Geddes JR, Harrison PJ & PHOSP-COVID Study Collaborative Group. (2023) “Acute blood biomarker profiles predict cognitive deficits 6 and 12 months after COVID-19 hospitalisation.” Nature Medicine, doi: 10.1038/s41591-023-02525-y
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