Blood clotting proteins could help predict post-Covid cognitive deficits

NEW DELHI: Two blood proteins, known to contribute to clotting, could help predict cognitive deficits 6 and 12 months after hospitalisation due to Covid, new research published in the journal Nature Medicine has found.

'Brain fog', or the inability to focus and pay attention, is one of the commonly reported post-Covid cognitive effects. Other such cognitive deficits include loss in executive function, memory, and learning.

The blood proteins, identified as fibrinogen and d-dimer, were highly correlated with post-acute COVID-19 cognitive deficits, the study from the University of Oxford, UK, found.

In this study, the researchers collected blood samples of 1,837 patients hospitalised for COVID-19 in the UK between January 29, 2020 and November 20, 2021.

They also got clinician-acquired and patient-reported data about the patients' cognition 6 and 12 months after hospital admission.

The clinician-acquired data was used in determining the Montreal Cognitive Assessment (MoCA) score, which measured the patients' objective cognitive deficits.

The patient-reported data was obtained through Patient Symptom Questionnaire (C-PSQ) and helped measure their subjective cognitive deficits.

Individuals with high levels of fibrinogen at the time of hospital admission relative to C-reactive protein (CRP), which is formed as a consequence of inflammation, showed significantly higher C-PSQ (subjective deficits) and lower MoCA score (objective deficits) at 6 and 12 months after Covid, the researchers found.

In other words, they wrote, high levels of fibrinogen compared to CRP were linked to signs of both objective and subjective cognitive deficits at 6 and 12 months after Covid.

The researchers also found that raised levels of d-dimer compared to CRP translated into significantly higher C-PSQ, but not lower MoCA, along with occupational outcomes at 6 and 12 months after Covid.

Thus, elevated levels of d-dimer compared to CRP were linked with subjective cognitive deficits, as well as signs of occupational impact such as an impaired ability to work or an occupational change, at 6 and 12 months, they wrote.

The researchers think that fibrinogen, indicative of inflammation, may directly affect the brain through brain cell damage and eventually, binding of amyloid-beta, suggesting dementia.

Previous studies have associated raised fibrinogen levels with cognitive deficit and subsequent dementia.

The findings of this study 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, suggesting the specificity of d-dimer for COVID-19, the authors said.

They also said that their findings may enable the development of models for post-COVID-19 cognitive deficits that could facilitate prognosis and management, even as further research is needed in more cohorts.