Researchers have warned that people recuperating from COVID-19 are likely to suffer significant brain function impacts, with the worst cases of the (coronavirus) infection linked to mental decline at par with the brain ageing by 10 years.
A non-peer-reviewed study of over 84,000 people, led by Adam Hampshire, a doctor at Imperial College London, discovered that in some cases, coronavirus infection is associated with substantial cognitive deficits for months.
The scientists wrote in a report of their findings that their analysis "aligns with the view that there are chronic cognitive consequences of having COVID-19" adding that people who had recovered from it, comprising those no longer reporting anymore symptoms, "exhibited significant cognitive deficits."
Cognitive tests measure how well the brain performs tasks -- such as remembering words or joining dots on a puzzle. Such tests are widely used to assess brain performance in diseases like Alzheimer's, and can also help doctors assess temporary brain impairments.
Hampshire's team analysed results from 84,285 people who completed a study called the Great British Intelligence Test.
The findings, which are yet to be reviewed by other experts, were published online on the MedRxiv website.
The cognitive deficits were "of substantial effect size", particularly among people who had been hospitalised with COVID-19, the researchers said, with the worst cases showing impacts "equivalent to the average 10-year decline in global performance between the ages of 20 to 70".
Scientists not directly involved with the study, however, said its results should be viewed with some caution. "The cognitive function of the participants was not known pre-COVID, and the results also do not reflect long-term recovery - so any effects on cognition may be short term," said Joanna Wardlaw, a professor of applied neuroimaging at Edinburgh University.
Derek Hill, a professor of medical imaging science at University College London, also noted that the study's findings could not be entirely reliable, since they did not compare before and after scores, and involved a large number of people who self-reported having had COVID-19, who had no positive test.