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Cognitive loss from severe Covid equates to 20 years of aging

Cognitive impairment as a result of severe COVID-19 is similar to 20 years of aging and is the equivalent to losing ten IQ points, says new research from the University of Cambridge and Imperial College London.

The results suggest that cognitive impairment is still detectable more than six months after the acute illness and recovery is gradual at best.

There is growing evidence that COVID-19 can cause lasting cognitive and mental health problems. Recovered patients have reported fatigue, “brain fog,” problems recalling words, sleep disturbances, anxiety and even post-traumatic stress disorder (PTSD) months after infection. In the UK, a study found that one in seven individuals reported cognitive difficulties 12 weeks after COVID-19.

To understand this link, the data of 46 individuals who received hospital or intensive care (mechanical ventilation) for COVID-19 from March to July 2020 was analyzed. These patients were at Addenbrooke’s Hospital, part of Cambridge University Hospital’s NHS Foundation.

Cognitive tests were used six months after the patient’s illness using the Cognitron platform, which measures mental faculties such as memory, attention and reasoning. Scales measuring anxiety, depression and post-traumatic stress disorder were also assessed. 

COVID-19 survivors were less accurate and had a slower response time than the control population. These symptoms were still detectable six months later. The effects were strongest for those who required ventilation. 

By comparing the patients to 66,008 members of the general public, the researchers estimate that the magnitude of cognitive loss is similar on average to that sustained with 20 years aging, between 50 and 70 years of age, and that this is equivalent to losing ten IQ points.

Survivors scored poorly on tasks such as verbal reasoning, supporting the commonly-reported problem of difficulty finding words. They also showed slower processing speeds, which aligns with post COVID-19 decreased brain glucose consumption within the frontoparietal network of the brain, responsible for attention, complex problem-solving and working memory.

“Cognitive impairment is common to a wide range of neurological disorders, including dementia, and even routine aging, but the patterns we saw – the cognitive ‘fingerprint’ of COVID-19 – was distinct from all of these,” explained study senior author Professor David Menon.

It has been well documented that people who have recovered from severe COVID-19 can have symptoms of poor mental health – depression, anxiety, post-traumatic stress, low motivation, fatigue, low mood, and disturbed sleep. However, the research team found that acute illness severity was better at predicting these cognitive deficits.

Over time, the patients’ scores and reaction times began to improve, however, recovery in cognitive faculties was at best gradual and likely to be influenced by a number of factors including illness severity and its neurological or psychological impacts. It is also considered likely that some individuals will never fully recover.

There are several factors that could cause the cognitive deficits, including inadequate oxygen or blood supply to the brain, blockage of large or small blood vessels due to clotting, and microscopic bleeds. Emerging evidence suggests that damage may be caused by the body’s own inflammatory response and immune system.

While this study looked at hospitalized cases, the team say that even those patients not sick enough to be admitted may also have tell-tale signs of mild impairment. This emphasizes the importance of exploring methods that could help patients recover. 

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.

“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,” said study first author Professor Adam Hampshire.

The research was funded by the NIHR BioResource, NIHR Cambridge Biomedical Research Centre and the Addenbrooke’s Charitable Trust.

By Katherine Bucko, Staff Writer

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