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People hospitalised with severe COVID-19 show cognitive decline similar to 20 years of ageing

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New research funded by NIHR shows that patients who were hospitalised with severe COVID have lasting cognitive problems several months after their acute illness. 

Researchers at the University of Cambridge and Imperial College London, funded by the NIHR COVID-19 Bioresource and NIHR Cambridge Biomedical Research Centre, analysed data from 46 patients who were treated in hospital for COVID-19. The patients were admitted to Addenbrooke’s Hospital in Cambridge between March and July 2020, early in the pandemic.

The patients in the study had detailed cognitive tests around three to six months after their acute illness, to measure mental faculties including memory, attention and reasoning. The results were compared against scores from over 66,000 members of the general public.

COVID-19 survivors showed less accurate responses and slower response times than the comparison group, performing particularly poorly on tasks such as verbal reasoning. They also showed slower processing speeds. The researchers estimated that the decline was similar to the average cognitive loss seen in the 20 years of ageing between ages 50 and 70.

The results support growing evidence that COVID-19 can cause lasting cognitive and mental health problems, with people who have recovered from their initial infection reporting symptoms such as ‘brain fog’ and difficulty recalling words.

Professor David Menon from the Division of Anaesthesia at the University of Cambridge, the study’s senior author, said: “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.”

Professor Menon added: “We followed some patients up as late as 10 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.”

The researchers believe that the virus itself is unlikely to be the main cause of the impairment - instead it is likely that a combination of factors contribute, including low blood or oxygen supply to the brain, blockage of blood vessels and microscopic bleeds in the brain. Another factor may be the body’s own immune response causing inflammation. 

Professor Adam Hampshire from the Department of Brain Sciences at Imperial College London, the study’s first author, said: “Around 40,000 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 is 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.”

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