People who have had corona can experience permanent cognitive complaints. Memory seems less affected than other features.
Corona can cause permanent brain problems, such as reduced concentration and a decline in thinking ability. This is now generally accepted in science. Memory, however, appears to be the least affected of all cognitive functions.
Most previous studies assessing the cognitive effects of corona have used tests designed to evaluate dementia. “These don’t give accurate measurements, nor really measure the variety of brain functions,” says neuroscientist Conor Wild of Western University in Ontario, Canada.
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To make a better analysis, Wild and his colleagues used a cognitive assessment tool developed by brain scientists at the British University of Cambridge. This online test measures cognition using twelve tasks in five domains: reasoning, verbal processing, memory, processing speed and general cognition.
Grown old young
The researchers asked 478 adults who had had corona to complete the test. The participants tested positive between one week and nine months before the start of the study. It is unknown whether the participants had had corona once or several times. About 14 percent said they ended up in hospital because of the illness.
The researchers compared the scores of these participants with those of 7,832 people who had taken the test before the pandemic. They found that the people who had had corona had significantly lower overall cognitive scores on average. Their decline was equivalent to the cognitive decline that occurs with age 4.5 years, Wild says. People who had been seriously ill had the worst scores. But people with a mild disease course were also cognitively less strong.
Memory saved?
Covid-19 appears to affect certain brain functions more than others. Processing speed was most affected. If you compare the scores of the corona patients in that area with those of the control group, it was as if the people who tested positive had become ‘older’ on average due to their disease, says Wild. Verbal processing and reasoning scores were also significantly lower in those who had had Covid-19.
Remarkably, the researchers found no significant differences in the functioning of memory. In previous studies, it seemed as if memory was deteriorating due to a covid infection.
“Memory is kind of an umbrella term, encompassing a number of different types of memory,” says Wild. He says the assessment tool used in this study is more focused on measuring short-term memory. That may explain the difference with previous studies.
Sleep problems
By identifying which aspects of cognition are affected by Covid-19, we can better understand lung covid, says neuroscientist Frederic Meunier of the University of Queensland in Australia. In addition, we may also be able to develop better treatments for the disease.
For example, previous research has shown that people who don’t get enough sleep experience similar problems: reduced processing capacity and general cognition, but an intact memory. That may indicate that the effects of Covid-19 are somehow related to broken nights.
Compare one-to-one
One caveat to the study is that it compared the scores of corona patients with scores from before the pandemic. As a result, the researchers cannot say with certainty that the differences are due to the disease. The stress of a global pandemic could also play a role, says Wild.
‘What we’re working on now is looking [op individueel niveau]: How people’s cognition after corona compares to their cognition before the pandemic,” he says.