Developing a test for long COVID 'brain fog'

Embargoed until: Publicly released: 2023-09-01 01:00

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Testing for two substances in blood - called blood biomarkers - may allow doctors to predict which COVID-19 patients will go on to develop cognitive problems, including 'brain fog', say UK scientists. The team looked at blood samples from more than 1800 British people hospitalised with COVID-19 between early 2020 and late 2021 who had self-reported any cognitive issues (subjective tests) and undergone cognition tests with clinicians (objective tests) six and 12 months after hospitalisation. Using statistics, the researchers were able to link two biomarkers to cognitive problems, both involved in blood clotting. The first was fibrinogen, which was linked with both objectively and subjectively measured cognitive problems. The second, d-dimer, was linked only with subjective problems, including ‘brain fog’, and also with fatigue and shortness of breath. The scientists tested their findings in another group of nearly 18,000 US patients, saying they were largely the same. The results are promising, but further research is required to develop this into a test for COVID-19-related cognitive problems, the researchers say.

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From: Springer Nature

COVID-19: Blood biomarkers may predict cognitive deficits following COVID-19

Two blood biomarkers could be predictive of cognitive deficits 6 and 12 months after diagnosis of COVID-19, reports a study published in Nature Medicine. These findings, based on data from over 1,800 patients who were admitted to the hospital with COVID-19, were validated in an independent dataset, and provide biological insights into factors that may drive long-term cognitive dysfunction due to COVID-19.

Post-COVID-19 cognitive deficits, including ‘brain fog’, can be debilitating and affect day-to-day life. Their diagnosis includes both objective (clinician-based) components and subjective (patient-reported) components. However, how these post-COVID-19 cognitive deficits develop remains unknown.

Maxime Taquet and colleagues examined data collected from 1,837 patients hospitalized for COVID-19 in the UK between 29 January 2020 and 20 November 2021. Blood samples were collected from these patents during admission to the hospital, and both clinician-acquired measurements and patient-reported measurements of cognition were obtained 6 and 12 months later. Using a statistical approach, the authors identified two blood biomarker profiles that were highly correlated with post-acute COVID-19 cognitive deficits. The first profile identified high levels of fibrinogen, a protein associated with blood coagulation, that correlated with both objective cognitive deficits and subjective cognitive deficits. The second profile associated elevated levels of another blood-coagulation protein, d-dimer, with subjective cognitive deficits, including ‘brain fog’, but also with fatigue and shortness of breath. The findings were largely replicated in a separate study of the health records of 17,911 patients in the USA, including comparison of post-pandemic cohorts versus pre-pandemic cohorts, which the authors suggest demonstrates the specificity of d-dimer for COVID-19.

The authors suggest that their findings may enable the development of models for post-COVID-19 cognitive deficits that could facilitate prognosis and management. However, they note that further research is needed in more cohorts.

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Journal/
conference: Nature Medicine

Research:Paper

Organisation/s: University of Oxford, UK

Funder: This work was funded by MQ Mental Health Research, the Wolfson Foundation, UK Research and Innovation (grant MR/V027859/1), National Institute of Health Research (grant COV0319) and the National Institute for Health and Care Research (NIHR) Oxford Health Biomedical Research Centre (grants BRC-1215-20005 and NIHR203316).

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