New research spotlights long COVID’s serious cognitive health repercussions, including a 6-point drop in IQ.
New research adds to piling scientific proof that long-COVID patients may suffer serious, long-term neurological damage that hurts their brain health and cognitive abilities, including early evidence linking a serious bout of long COVID with drops in IQ and trouble with standard memory-related and cognitive tasks like verbal reasoning and accurately defining words.
The findings are detailed in a pair of new studies published in The New England Journal of Medicine examining the cognitive abilities of nearly 200,000 participants with COVID-19 test results in England and Norway who completed follow-up cognition and memory task assessments months after their original baseline test. In England, researchers found that the longer it took someone with COVID-19 to recover from their symptoms, the more that person’s measurable IQ dropped compared with those who never had a positive COVID-19 test.
Those who recovered within a few weeks fared about 3 IQ points lower than those without a positive test, while people with long COVID—infections with symptoms that persisted for 12 or more weeks—demonstrated a 6-point drop in IQ. The pandemic’s earliest COVID-19 strains were associated with the sharpest declines in standard cognition tests measuring skills like spatial and verbal reasoning, as well as long- and short-term memory.
“We found objectively measurable cognitive deficits that may persist for a year or more after COVID-19,” wrote the authors of the English study, noting that illness severity (such as cases requiring hospital visits) were associated with more severe cognitive repercussions. “Early periods of the pandemic, longer illness duration, and hospitalization had the strongest associations with global cognitive deficits. The implications of longer-term persistence of cognitive deficits and their clinical relevance remain unclear and warrant ongoing surveillance,” they wrote.
The second study, from Norway, found even more troubling long-term memory implications of more severe COVID-19 that could persist for years. More than 134,000 participants in this study who recovered from a confirmed COVID-19 case regularly took a test called the Everyday Memory Questionnaire. Those who were admitted to an ICU or hospitalized, and those who hadn’t kept up with their COVID-19 vaccinations or were infected earlier in the pandemic, fared markedly worse at various points over more than 36 months. Those findings align with the study results from England.
“We found smaller cognitive deficits among participants who had been infected during recent variant periods than among those who had been infected with the original virus or the alpha variant,” wrote the researchers. “We also found a small cognitive advantage among participants who had received two or more vaccinations and a minimal effect of repeat episodes of COVID-19.” Notably, these studies were observational analyses based on volunteer responses and follow-ups, which come with some caveats compared to randomized clinical trials.
Scientists have gathered clues in the four years since the COVID-19 pandemic’s outbreak on how the virus negatively affects the brain, including damaging brain inflammation caused by an aggressive and persistent immune response to a particularly stubborn, symptomatic infection.
Other experts noted that the new NEJM studies observing IQ drops, memory declines, and reasoning capacity shortfalls underscore the reality that long COVID is real and has tangible effects—whose long-term consequences are still unclear but need to be measured with rigorous follow-up.
“Unfortunately, there will continue to be people who will attempt to dismiss or discount the important effects of COVID on cognitive function,” wrote Eric Topol, renowned epidemiologist and director of the Scripps Research Translational Institute, in a post on his Ground Truths Substack examining the latest research. “Just the opposite of denialism is what is needed—to recognize this cognitive impairment is real, that millions of people are affected, and much more needs to be done to find effective treatments of long COVID and understand its longer-term impact, particularly neurologic.”