Long Covid can lead to measurable cognitive decline, study finds

Long Covid can cause measurable cognitive impairment, especially in the ability to remember, reason and plan, a major new study suggests.

Cognitive testing of nearly 113,000 people in England found that those with lingering post-Covid symptoms scored the equivalent of 6 IQ points lower than people who had never been infected with the coronavirus, according to the study, published Wednesday in The New England Journal of Medicine. .

People who had been infected and no longer had symptoms also scored slightly lower than people who had never been infected, by the equivalent of 3 IQ points, even if they were sick for only a short time.

The differences in cognitive scores were relatively small and neurology experts cautioned that the results did not imply that being infected with the coronavirus or developing long Covid caused profound deficits in thinking and function. But experts said the findings are important because they provide numerical evidence of the brain fog, concentration and memory problems that affect many people with long Covid.

“These emerging and conflating findings generally highlight that yes, there is cognitive decline in long-term Covid survivors; it is a real phenomenon,” said James C. Jackson, a neuropsychologist at Vanderbilt Medical Center, who was not involved in the study.

He and other experts noted that the results were consistent with smaller studies that have found signs of cognitive decline.

The new study also found reason for optimism, suggesting that if people’s long Covid symptoms subside, the related cognitive decline could too: People who had experienced long Covid symptoms for months and eventually recovered had scores cognitive abilities similar to those who had experienced rapid recovery. , the study found.

On a typical IQ scale, people with a score of 85 to 115 are considered to be of average intelligence. The standard variation is about 15 points, so a change of 3 points is not usually considered significant and a change of even 6 points may be inconsequential, experts said.

“The question is: are people capable of functioning in their routine capacity in whatever they are doing? And this is not really answered by 3 points or so,” said Dr. Igor Koralnik, chief of neuroinfectious diseases and global neurology at Northwestern Medicine in Chicago, who was not involved in the study.

He added: “Determining X points on an IQ scale is less important than people’s perception of their cognitive difficulties.”

Still, Dr. Jackson, author of a book about long Covid called “Clearing the Fog,” said that while cognitive tests like the one in the study “identify relatively mild deficits,” even subtle difficulties can be important for some. people. For example, he said, “if you’re an engineer and you have a slight decline in executive functioning, that’s a problem.”

The study, led by researchers at Imperial College London, involved 112,964 adults who completed an online cognitive assessment during the last five months of 2022. About 46,000 of them, or 41 percent, said they had never had Covid. Another 46,000 people who had been infected with the coronavirus said their illness had lasted less than four weeks.

Around 3,200 people had post-Covid symptoms lasting four to 12 weeks after their infection, and around 3,900 people had symptoms beyond 12 weeks, including some that lasted a year or more. Of them, 2,580 people still had post-Covid symptoms at the time they took the cognitive test.

The researchers noted that they were based on self-reported symptoms, rather than long Covid diagnoses, and that the demands of taking a cognitive test could have meant that study participants were not the most severely affected.