New Study Suggests High Levels of Cognitive Decline Post-COVID Linked to Immune Function

24 Jun, 2022 F.J. Thomas


Sarasota, FL ( – Researchers are just now starting to understand the full potential effects that the SARS-CoV-2 virus can have on the brain. One of the common complaints in addition to loss of smell has been ‘brain fog’ that can last several months.


One small study published earlier this year found elevated protein levels in the spinal fluid of patients who were 10 months post-COVID and had reported brain fog. The elevated protein levels suggested high levels of systemic inflammation brought on by an autoimmune type response.

In yet another recent study, researchers have found that the SARS-CoV-2 can impact cognitive abilities via the immune system, as indicated by kynurenine pathway (KP) activation. The kynurenine pathway is a metabolic pathway that is a key regulator of the immune system, and can be an indicator of inflammation and autoimmune issues, especially in regards to neurological conditions.

Researchers from the St. Vincent's Centre for Applied Medical Research in Australia studied 128 unvaccinated patients with confirmed SARS-CoV-2 infection, with the first exam in May 2020. The researchers did a neurocognitive assessment, and conducted bloodwork measuring blood cytokine levels, KP metabolites, and other key cells.     

After the initial assessment, follow ups were done at 2, 4, and 12 months after diagnosis. Olfactive function, as well as mental and physical health, and lung function were reviewed at 2 months post COVID. Participants were classified into three categories based on acute severity – mild, moderate, severe.

To assess neurocognitive levels, the CogState Computerized Battery (CCB) screening test was used to assess detection reaction time, identification reaction time, one card learning accuracy, and learning reaction time and accuracy. Tasks that were used in the study were selected specifically for COVID cases as they targeted abilities normally impacted by acute respiratory illnesses, immune compromise, and cerebrovascular diseases.

Overall, the researchers found a mild but significant decline in cognitive performance. Those that reported loss of smell at 2 months post diagnosis were more likely to have cognitive impairment, but that was only noted at the 2-month marker. Sixteen percent of the participants had mild to moderate impairment 2 months after diagnosis. In four months, 23 percent of the participants had mild to moderate cognitive impairment, and at 12 months the percentage increased to 26 percent.

The researchers also noted a direct correlation between cognitive decline and the levels of KP metabolites quinolinic acid, 3-hydroxyanthranilic acid, and kynurenine. The researchers believe this correlation offers a possible direct target in treating cognitive impairment related to COVID-19.



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    About The Author

    • F.J. Thomas

      F.J. Thomas has worked in healthcare business for more than fifteen years in Tennessee. Her experience as a contract appeals analyst has given her an intimate grasp of the inner workings of both the provider and insurance world. Knowing first hand that the industry is constantly changing, she strives to find resources and information you can use.

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