Feb. 29, 2024 – People who recovered from COVID-19 showed small loss of cognitive ability equal to a 3-point loss in IQ for up to 1 year after recovering, while more serious cases of COVID were tied to a much higher loss of brain function, a new study found.
The study from the United Kingdom found that people who had more severe cases of COVID, requiring treatment in a hospital intensive care unit, had cognitive deficits equivalent to a 9-point drop in IQ.
The largest deficits among cognitive tasks were in memory, reasoning, and executive function, Adam Hampshire, PhD, with Imperial College London, said..
"People who had had COVID-19 were both slower and less accurate when performing tasks that measure those abilities," Hampshire said.
The study was published online Wednesday in The New England Journal of Medicine.
Lingering Brain Fog
Cognitive symptoms after COVID are well recognized, but whether actual cognitive deficits exist and how long they persist remains unclear.
To investigate, researchers invited 800,000 adults from the Real-Time Assessment of Community Transmission study of coronavirus transmission in England to complete an online assessment for cognitive function with eight sections.
Altogether, 141,583 participants started the cognitive battery by completing at least one task, and 112,964 completed all eight tasks.
Compared with uninfected adults, those who had COVID-19 and recovered had a small cognitive deficit, corresponding to a 3-point loss in IQ, the researchers found.
Adults with persistent COVID-19 symptoms had the equivalent of a 6-point loss in IQ, and those who had been admitted to the intensive care unit had the equivalent of a 9-point loss in IQ, the researchers report.
Larger problems were found in adults infected early in the pandemic by the original virus variant or the B.1.1.7 variant, while those infected later in the pandemic (eg, in the Omicron period), showed smaller cognitive declines .
They also found that people who had COVID-19 after receiving two or more vaccinations showed better cognitive performance compared with those who had not been vaccinated.
The memory, reasoning, and executive function tasks were among the most sensitive to COVID-19–related problems and performance on these tasks was different based on how long symptoms lasted and whether the person was hospitalized.
Hampshire said that more research is needed to determine whether the cognitive deficits resolve with time.
Larger Cognitive Deficits Likely?
These results are "a concern and the broader implications require evaluation," wrote Ziyad Al-Aly, MD, with Washington University School of Medicine in St. Louis, and Clifford Rosen, MD, with Tufts University School of Medicine in Boston, in an accompanying editorial.
In their view, several outstanding questions remain, including what the potential impacts are of a 3-point loss in IQ and whether COVID-19–related cognitive issues could mean a a higher risk for dementia later in life.
Commenting on the study, Jacqueline Becker, PhD, clinical neuropsychologist and assistant professor of medicine at the Icahn School of Medicine at Mount Sinai, New York City, said "one important caveat" is that the study used an online assessment tool for cognitive function and therefore the findings should be taken with "a grain of salt."
"That said, this is a large sample, and the findings are generally consistent with what we've seen in terms of cognitive deficits post-COVID," Becker said.
It's likely that this study "underestimates" the degree of cognitive deficits that would be seen on neuropsychological tests, she said.
In a recent study, Becker and her colleagues investigated rates of cognitive impairment in 740 COVID-19 patients who recovered and were treated in outpatient, emergency department, or inpatient hospital settings.
Using validated neuropsychological measures, they found a relatively high frequency of cognitive impairment several months after patients contracted COVID-19. Impairments in executive functioning, processing speed, category fluency, memory encoding, and recall were predominant among hospitalized patients.
