Cognitive impairment from long COVID equivalent to aging 20 years, study finds

Exploring the effects of long COVID on the brain Dr. Roger McIntyre, a professor of psychiatry and pharmacology at the University of Toronto, discusses how long COVID affects the brain.

A new study says that cognitive impairment due to long COVID is the equivalent of aging 20 years or losing 10 IQ points.

Researchers from the University of Cambridge and Imperial College London published their findings in the journal eClinicalMedicine last week. They looked at data from 46 individuals who received care at a hospital for COVID-19 between March and July 2020 and compared them to a matched control group.

Six months after their stay in hospital, the researchers invited the patients and the control group to undergo a computerized test to measure their memory, attention and reasoning. The researchers found that compared to the control group, those who had been hospitalized with COVID-19 were less accurate and displayed slower response times in the test.

"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," senior author Dr. David Menon of the University of Cambridge said in a news release published last Tuesday.

Those who had COVID-19 scored especially poorly on verbal analogical reasoning and exhibited slower processing speeds. In addition, those who had more severe cases of COVID-19 were also found to be more likely to do poorer on these tests.

These results were "similar in magnitude to the effects of ageing between 50 and 70 years of age," the authors wrote.

They say these findings also line up with a 2021 German study that found that COVID-19 could induce a decrease in brain glucose consumption within the parts of the brain responsible for attention, problem solving and memory.

The Public Health Agency of Canada (PHAC) has documented reports of more than 100 potential symptoms of long COVID. The most common ones, according to PHAC, include fatigue, memory problems, anxiety, depression and even post-traumatic stress disorder.

It's unclear how many people are affected by long COVID symptoms. Early data from the World Health Organization showed that 10 to 20 per cent of those infected with the virus could go on to become COVID long-haulers, but Tam said on Friday that more up-to-date research indicates it could actually be as high as 50 per cent.

It's still not completely clear how COVID-19 can cause long-term cognitive deficits, but researchers say it may be caused by the immune system's inflammatory response. Inadequate oxygen or blood supply to the brain, blood clotting and microscopic bleeding are also possible factors.

The researchers continued to follow up with the patients up to 10 months following their infection, and some patients did show small signs of improvement.

"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," Memon said.