Why Covid’s long-term impact on brain needs attention

Why Covid’s long-term impact on brain needs attention
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The lasting impact of a severe Covid-19 infection on the brain in areas such as memory, attention, or problem solving may be equivalent to 20 years of ageing, a UK study has found.

The new research, led by a team of scientists from the University of Cambridge and Imperial College London, suggests that cognitive impairment as a result of severe Covid-19 is similar to that sustained between 50 and 70 years of age and is the equivalent to losing 10 IQ points.

“Cognitive impairment is common to a wide range of neurological disorders, including dementia, and even routine ageing, but the patterns we saw – the cognitive 'fingerprint' of Covid-19 – was distinct from all of these,” said Professor David Menon, from the Division of Anaesthesia at the University of Cambridge, the study’s senior author.

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The research, published in the journal ‘eClinicalMedicine’ last week, indicates the effects are still detectable more than six months after acute illness and that any recovery is very gradual.

“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,” said Professor Adam Hampshire, from the Department of Brain Sciences at Imperial College London.

“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,” he said.

According to the researchers, this is the first time that such rigorous assessment and comparison has been carried out in relation to the after-effects of severe Covid-19. There have been growing reports that Covid-19 can cause lasting cognitive and mental health problems, with recovered patients reporting symptoms including fatigue, “brain fog”, problems recalling words, sleep disturbances, anxiety and even post-traumatic stress disorder (PTSD) months after infection.

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The researchers behind the latest study analysed data from 46 people who received in-hospital care, on the ward or intensive care unit, for Covid-19, 16 of whom were put on mechanical ventilation during their stay in hospital. All of the patients were admitted to Addenbrooke’s Hospital in Cambridge between March and July 2020 and went on to take cognitive tests an average of six months after their illness using the Cognitron platform, which measures different aspects of mental faculties such as memory, attention and reasoning. Scales measuring anxiety, depression and post-traumatic stress disorder were also assessed. The data was then compared against matched controls.

Analysis of the data revealed Covid-19 survivors were less accurate and had slower response times than the matched control population. These deficits were still detectable when the patients were following up six months later.

“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,” noted Professor Menon.

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The effects were strongest for those who required mechanical ventilation. Survivors scored particularly poorly on tasks such as verbal analogical reasoning, a finding that supports the commonly-reported problem of difficulty finding words. They also showed slower processing speeds, which aligns with previous observations post Covid-19 of decreased brain glucose consumption within the frontoparietal network of the brain, responsible for attention, complex problem-solving and working memory, among other functions.

While this study looked at hospitalised cases, the team say that even those patients not sick enough to be admitted may also have tell-tale signs of mild impairment.

The research was funded by the National Institute for Health and Care Research (NIHR) BioResource, NIHR Cambridge Biomedical Research Centre and the Addenbrooke’s Charitable Trust.

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