COVID-19 may cause some people’s brains to age by around 10 years when compared with those who have not had the disease, according to a preliminary study.
Over 84,000 people in the U.K. who said they had recovered from a suspected or confirmed case of COVID-19 completed a questionnaire that measured their thinking skills. The paper was submitted to the preprint server medRxiv, meaning it has not been through the rigorous peer review process that is required for publication in a scientific journal, so the findings should be interpreted with caution.
The participants took tests to measure their ability to solve problems, spatial memory, attention, and how they processed emotions.
Respondents said whether they had, or suspected they had, COVID-19. They were asked how long their symptoms lasted, as well as the severity of the disease and whether they had any underlying medical conditions. Their results were compared to those of healthy participants, who acted as the control group.
Participants who said they had COVID-19 performed worse on cognitive tests than those from the control group.
The link was particularly strong for those with severe COVID-19, but was also apparent in those had a mild form of the disease. A mild COVID-19 case was defined in the study as someone who did not have breathing problems.
The team uncovered “particularly pronounced problems” with what is known as higher cognition. The issues related to participants’ attention and reasoning, particularly verbal reasoning, study co-author Adam Hampshire of the department Brain Sciences at the U.K’s Imperial College London told Newsweek.
Patients aged 20 to 70 years old who were hospitalized and put on a ventilator to help with their breathing saw their thinking skills decline to the level of a person 10 years their senior, on average.
Hampshire told Newsweek the only significant predictors of cognitive problems were the severity of the patient’s respiratory symptoms and a positive test. No other variables, like whether a person had a pre-existing condition, accounted for the issues the team observed, he said.
The team said their data suggested “there are chronic cognitive consequences of having COVID-19,” and that their work comes amid growing evidence from separate studies that COVID-19 patients can suffer neurological problems due to complications such as strokes, the immune system overreacting and inflammation.
“These results should act as a clarion call for more detailed research investigating the basis of cognitive deficits in people who have survived SARS-COV-2 [coronavirus] infection,” the authors wrote.
Experts who were not involved in the study said the findings not prove that COVID-19 causes thinking problems.
In a statement, Joanna Wardlaw, professor of applied neuroimaging at the U.K.’s University of Edinburgh, said the study was limited because the team did not have information about the participants’ cognitive function before they had COVID-19. The issues they uncovered may also be short term, she said.
Derek Hill, professor of medicaI imaging science at UCL in the U.K., said in a statement that the study was “an intriguing but inconclusive piece of research.” He said the information may not be reliable as the researchers relied on participants reporting their own symptoms, and said only a “tiny fraction” had a positive coronavirus test.
Hill also said the team did not explore how COVID-19 affects the brain biologically, for instance via scans. “It is well known that cognitive decline in Alzheimer’s disease is associated with shrinkage of the brain as determined by MRI scans,” said Hill.
David Strain, senior clinical lecturer at the University of Exeter, U.K., said in a statement the finding that the brains of some with COVID-19 aged approximately 10 years compared to those without the disease “is much worse” than what is seen in other people who have recovered from other viruses.
The team are still recruiting people for their study, which can be completed by clicking here. The results are limited as just 361 of the 84,000 participants had tested positive for the virus. Hampshire said the number reflects the proportion of the U.K. population who had been tested for the virus at the time the study was carried out. “We are still recruiting and will be tracking people to see whether they suffer a cognitive ability drop if they have COVID-19,” He said.