In the UK, one study found that around one in seven people surveyed reported symptoms including cognitive difficulties 12 weeks after testing positive for COVID-19.
While even mild cases can lead to persistent cognitive symptoms, between one-third and three-quarters of hospitalized patients report cognitive symptoms three to six months later. .
To explore this link in more detail, the researchers analyzed data from 46 individuals receiving hospital care, in the department or intensive care unit, for COVID-19 at Addenbrooke Hospital , part of Cambridge University Hospitals NHS Foundation Trust. 16 patients were mechanically ventilated during their hospital stay. All patients were admitted between March and July 2020 and enrolled in the NIHR COVID-19 BioResource.
Individuals underwent detailed computerized cognitive tests an average of six months after acute illness using the Cognitron platform, which measures various aspects of mental abilities such as memory, attention, and reasoning. Scales of anxiety, depression, and post-traumatic stress disorder were also assessed. Their data were compared with suitable controls.
This is the first time that such rigorous assessment and comparison has been made regarding the consequences of severe COVID-19.
COVID-19 survivors were less accurate and with slower response times than matched controls – and these deficits were still detectable when patients were followed up six months later. The effects are strongest for those requiring mechanical ventilation. By comparing the patients with 66,008 members of the public, the researchers estimated that the average level of cognitive loss was similar to that of the median cognitive loss equivalent to that maintained over 20 years of aging. , from age 50 to 70, and this equates to a decrease in IQ of 10. point.
Survivors scored particularly poorly on tasks such as verbal deductive reasoning, a finding that supports commonly reported difficulty finding words. They also showed slower processing speeds, consistent with previous observations posted by COVID-19 of reduced brain glucose consumption in the brain’s anterior parietal network, responsible for attention, problem solving, and attention. complex problems and working memory, among other functions.
Professor David Menon from the Department of Anesthesiology at the University of Cambridge, lead author of the study, said: “Cognitive impairment is common to a wide range of neurological disorders, including dementia and even dementia. even regular aging, but the patterns we see – the cognitive “fingerprint” of COVID-19 – are distinct from all of this.”
Although it is now well established that people who have recovered from severe COVID-19 illness can have many symptoms of poor mental health – depression, anxiety, post-traumatic stress, low motivation, fatigue, low mood and sleep disturbances – the team found that acute illness severity was better at predicting cognitive decline.
Patients’ scores and reaction times start to improve over time, but researchers say any recovery in cognitive ability is best gradual and likely to be affected. by a number of factors including the severity of the illness and its neurological or psychological effects.
Professor Menon added: “We’ve been following some patients for as late as ten months after they’ve had an acute infection, so we can see very slow improvement. Although this is by no means significant. statistically significant, but at least it’s moving in the right direction, but chances are some of these people will never fully recover.”
What factors cause cognitive decline in COVID-19 survivors?
There are several factors that can cause cognitive deficits, the researchers say. Direct virus transmission is possible, but not the primary cause; rather, it’s more likely a combination of factors, including insufficient oxygen or blood supply to the brain, blockage of large or small blood vessels due to clotting, and microscopic bleeding. However, emerging evidence suggests that the most important mechanism may be damage caused by the body’s own immune system and inflammatory response.
While this study looked at hospitalizations, the team says that even patients who aren’t sick enough to be hospitalized can show signs of mild impairment.
Professor Adam Hampshire at Imperial College London, first author of the study, said: “Around 40,000 people are already in intensive care with COVID-19 in the UK alone, and many more will become critically ill, but This means that there are a large number of people out there who still have cognitive problems months later. We urgently need to see what can be done to help. these people. “
Professor Menon and Professor Ed Bullmore from Cambridge’s Department of Psychiatry are co-lead groups working within the COVID-19 Clinical Neuroscience (COVID-CNS) Study to identify biomarkers associated with the disease. associated with neurologic impairment due to COVID-19, and neuroimaging changes are associated with these changes.