People infected with COVID-19 continue to have deficits in cognitive and memory abilities that last a year or more after infection, according to a study published on Feb 29.

The study by Imperial College London researchers reveals the cognitive deficits were larger for people who were hospitalised, who had ongoing long-duration symptoms, or who were infected with earlier variants of the virus.

The study, published in the New England Journal of Medicine, enrolled more than 140,000 participants, who undertook at least one cognitive task, with many having experienced COVID at various levels of severity and persistence.

The findings revealed small deficits that were still detectable a year or more after infection, even in people who had short-duration illness.

The deficits were found in multiple areas of cognition, most notably in memory, such as the ability to remember pictures of objects that were viewed a few minutes earlier. This may be due to problems forming new memories rather than accelerated forgetting, said the researchers.

Small deficits were also found in some tasks testing executive and reasoning abilities, such as those that require spatial planning or verbal reasoning.

Further, the deficits were found larger for people who had symptoms lasting 12 weeks or more (consistent with Long COVID), those who had been to the hospital for their illness or those who were infected with one of the early variants of the SARS-CoV-2 virus.

“The potential long-term effects of COVID-19 on cognitive function have been a concern for the public, healthcare professionals, and policymakers, but until now it has been difficult to objectively measure them in a large population sample,” said first author Professor Adam Hampshire, from the Department of Brain Sciences at Imperial.

“By using our online platform to measure multiple aspects of cognition and memory at a large scale, we were able to detect small but measurable deficits in cognitive task performance. We also found that people were likely affected in different ways depending on factors such as illness duration, virus variant and hospitalisation,” he added.