Cognitive impairment as a result of severe COVID-19 is similar to that sustained between 50 and 70 years of age and is equivalent to losing 10 IQ points, according to a team of scientists from the University of Cambridge and Imperial College London.
The results of the study suggest the effects are still detectable more than six months after the acute illness, and that any recovery is at best gradual.
COVID-19 has a potential to result in lasting cognitive and mental health problems, with recovered patients reporting symptoms such as fatigue, brain fog, problems recalling words, sleep disturbances, and even post-traumatic stress disorder (PTSD) months after infection. In the United Kingdom, a study found that one in seven individuals surveyed expressed a series of cognitive difficulties 12 weeks after a positive COVID-19 test.
Evenmild cases can result in persistent cognitive symptoms, yet between a third and three-quarters of hospitalized patients have reported developing cognitive symptoms three to six months later.
Researchers analysed data from 46 individuals who received COVID-19 at Addenbrookes Hospital, a part of the Cambridge University Hospitals NHS Foundation Trust, for in-hospital care. 16 patients were placed on mechanical ventilation during their stay at the hospital. All of the patients were then recruited to the NIHR COVID-19 BioResource.
On the Cognitron platform, individuals performed detailed cognitive tests for acute illness, measuring memory, attention, and reasoning. Scales also weighed anxiety, depression, and post-traumatic stress disorder. Their results were compared to comparable controls.
This is the first time that a so much thorough assessment and comparison has been made in relation to the effects of severe COVID-19.
COVID-19 survivors were less accurate and with shorter response times than the matched control population, and these shortcomings were still detectable when the patients were following up six months later. Researchers found that the magnitude of cognitive loss is similar to that sustained with 20 years ageing, between 50 and 70 years of age, and that this is equivalent to losing 10 IQ points.
Survivors performed particularly poorly on tasks such as verbal analogical reasoning, a finding that highlights the commonly-reported challenge of difficulty finding words. They also showed reduced processing speeds, which aligns with previous observations post COVID-19 of decreased brain glucose consumption within the frontoparietal cortex of the brain, responsible for attention, complex problem-solving and working memory.
According to the senior author of the study, Professor David Menon of the Division of Anaesthesia at the University of Cambridge said that cognitive impairment is common to a wide variety of neurological disorders, including dementia and even routine ageing, but the patterns we observed was different from all of them.
It is still well known that individuals who have recovered from the severe COVID-19 illness can have a broad spectrum of symptoms of poor mental health depression, anxiety, post-traumatic stress, low motivation, fatigue, low mood, and disturbed sleep. Moreover, the study found that acute illness severity is beneficial in understanding cognitive deficiencies.
Patients'' scores and reaction times improved as a result of the advancement in cognitive abilities, but experts say recovery in cognitive abilities was at best gradual and likely to be influenced by a variety of factors, including illness severity and its neurological or psychological effects.
Professor Menon said: We monitored some patients until ten months after their acute infection, so they were able to see a very slow improvement. Although this was not statistically significant, it is at least heading in the right direction, but it is very probable that some of these individuals will never complete recovery.
Researchers say there are several factors that might alter cognitive deficits.Direct viral infection is possible, but it is unlikely to be a major cause; instead, it is more likely that a combination of factors may influence, such as inadequate oxygen or blood supply to the brain, blockage of large or small blood vessels due to clotting, and microscopic bleedings. However, emerging evidence suggests that the most important mechanism may be damage caused by the body''s own inflammatory response and immune system.
Despite this approach to hospitalization situations, the research claims that even those who are not sick enough to be admitted may have mild impairment in all cases.
According to Professor Adam Hampshire from the Department of Brain Sciences at Imperial College London, the first author, 40,000 people have been intensive care with COVID-19 alone, and many more will have been very sick, but not admitted to hospital. This means there is a large number of people out there already experiencing cognition difficulties many months later. We need to investigate what can be done to assist these people.
As part of the COVID-19 Clinical Neuroscience Study (COVID-CNS), Professor Menon and Professor Ed Bullmore are co-leading working groups. They aim to identify biomarkers that relate to neurological impairments as a result of COVID-19, and the neuroimaging changes that are involved.