Covid-19 appears to affect memory less than other aspects of cognition

People who have had covid-19 can have lingering impairments in multiple aspects of cognition, but memory appears to be less affected

By Grace Wade

People who have had covid-19 can have lingering impairments in multiple aspects of cognition, but memory appears to be less affected.

While it is now well accepted that covid-19 can cause lingering declines in cognition, among other symptoms, most previous studies assessing this used tests meant for evaluating dementia. “These tests don’t provide very subtle measures, and they don’t really measure a variety of brain functions,” says Conor Wild at Western University in Ontario, Canada.

To provide a more sensitive analysis, Wild and his colleagues used the Cambridge Brain Sciences online cognitive assessment tool, which measures cognition using 12 tasks across five domains: reasoning, verbal processing, memory, processing speed and overall cognition.

The researchers asked 478 adults who reported a prior infection with covid-19 to complete the test. Participants tested positive between one week and nine months before the study, and it is unknown if any had contracted the virus more than once. About 14 per cent said they were hospitalised for their illness.

The researchers then compared participants’ scores to those of 7832 people who completed the assessment before the pandemic. They found that, on average, those people who had reported a prior covid-19 infection had significantly lower overall cognitive scores – the equivalent of ageing approximately 4.5 years, says Wild. Those with more severe infections had the worst scores, but even people with mild illness saw impairments.

Covid-19 appeared to impact certain brain functions more than others. Processing speed was impaired the most, with average scores lower than the control group by the equivalent of aging 8.5 years, says Wild. On average, scores for verbal processing and reasoning were also significantly lower in those who had reported contracting covid-19.

Notably, the researchers didn’t find any significant differences in memory, even though other studies have. “Memory is kind of an umbrella term that encapsulates a few different types of memory,” says Wild. He says that the assessment tool used in this study skews more towards measuring short-term memory, which may explain the discrepancies.

By pinpointing which areas of cognition covid-19 affects, we can not only better understand long covid, but also potentially develop more precise treatments for the condition, says Frederic Meunier at The University of Queensland in Australia.

For example, previous research has shown a similar pattern of impairment – with reductions in processing and overall cognition but not memory – in people who don’t get enough sleep, says Wild, suggesting the effects of covid-19 may be somehow related to sleep disturbances.

However, because the study compared the scores of people with a history of covid-19 with those of people studied before the pandemic, researchers can’t conclusively say the observed differences were due to illness. It is possible that the stress of living through a pandemic may also have played a role, says Wild.

“What we’re working on next is actually looking at how people compare to their pre-pandemic self in terms of cognition,” he says.

Journal reference: Cell reports Medicine, DOI: 10.1016/j.xcrm.2022.100750