The lasting impacts of severe Covid on cognitive functioning, such as memory and problem solving, may be the equivalent to 20 years of ageing, a new study has found.
New findings suggest patients who overcome severe coronavirus illness suffer similar cognitive impairment that people typically go through between the ages of 50 and 70.
This is the equivalent of losing 10 IQ points, say a team of scientists from Imperial College London and the University of Cambridge, who conducted the study.
The research indicates the mental effects of Covid infection are still detectable more than six months after acute illness and any recovery from this is, at best, gradual. Even people who had mild cases may be impacted.
Researchers say this means a large number of people will still be experiencing cognitive problems many months after recovery - and more must be done to help them.
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Professor Adam Hampshire, of the Department of Brain Sciences at Imperial College London and first author of the study, said: “Tens of thousands of people have been through intensive care with COVID-19 in England alone and many more will have been very sick, but not admitted to hospital.
"This means there are a large number of people out there still experiencing problems with cognition many months later.
"We urgently need to look at what can be done to help these people.”
There is growing evidence coronavirus can cause lasting cognitive and mental health problems.
Patients have reported symptoms months after infection, including fatigue, "brain fog", problems recalling words, sleep disturbances, anxiety and even post-traumatic stress disorder (PTSD).
An earlier study in the UK found around one in seven surveyed reported having symptoms including cognitive difficulties 12 weeks after a positive Covid test.
Even mild cases can lead to persistent cognitive symptoms, with between a third and three-quarters of hospitalised patients reporting that they still suffer symptoms three to six months later.
How was the study carried out?
Imperial College London and University of Cambridge researchers analysed data from 46 people who received in-hospital care (on the ward or intensive care unit) for Covid at Addenbrooke’s Hospital, Cambridge, between March and July 2020. Of those, 16 needed to be put on mechanical ventilation during their stay.
The patients took cognitive tests on average six months after recovering from their illness, to measure different aspects of mental faculty such as memory, attention and reasoning, while anxiety, depression and PTSD were also assessed.
Analysis of the data revealed Covid survivors were less accurate and had slower response times than the matched control population - and these deficits were still detectable when the patients were followed up six months later.
The impacts were strongest for those who were put on ventilators.
Having compared the patients to 66,008 members of the general public, the researchers estimate that the level of cognitive loss is similar on average to that sustained with 20 years ageing, between 50 and 70 years of age.
They scored particularly poorly on tasks such as verbal analogical reasoning - a finding that supports the commonly-reported problem of difficulty finding words - and showed slower processing speeds.
Professor David Menon, from the Division of Anaesthesia at the University of Cambridge and the study’s senior author, added: “We followed some patients up as late as ten months after their acute infection, so were able to see a very slow improvement.
"While this was not statistically significant, it is at least heading in the right direction, but it is very possible that some of these individuals will never fully recover.”
Researchers say the study, published in the journal eClinicalMedicine, is the first time such a rigorous assessment has been carried out into the after-effects of severe Covid.