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Severe COVID-19 may cause similar cognitive deficits as 20 years of aging

middle aged man sitting and looking at laptop with slight confusion and frustration
Severe COVID-19 infections that required hospitalization have been linked to cognitive deficits. (Image credit: JohnnyGreig via Getty Images)

People who require hospitalization for COVID-19 develop lingering cognitive problems similar to what you'd expect if they'd aged 20 years.

That's according to a new study conducted in the United Kingdom and published online on April 28 in the journal eClinicalMedicine (opens in new tab). The research is somewhat limited in that it included fewer than 50 COVID-19 patients, but it adds to the ample body of research already suggesting that the coronavirus infection leaves a lasting impact on the brain.

For example, a 2021 study showed that many COVID long-haulers — those who experience various symptoms for weeks or months after their initial infection — reported experiencing multiple brain-related symptoms, including "brain fog," or trouble thinking, headache and the loss of sense of smell or taste, Live Science previously reported. These lingering symptoms weren't unique to those who developed severe COVID-19 infections, but also affected those who experienced only mild illness, according to the study. 

More recently, a large study found distinct patterns of brain shrinkage in hundreds of people who previously caught COVID-19, and it's possible that this abnormal atrophy may contribute to patients' observed cognitive deficits, the authors suggested. 

Related: 20 of the worst epidemics and pandemics in history

The new U.K. study zoomed in on severe COVID-19 cases that required hospitalization and assessed how those patients fared on cognitive tests about six to 10 months down the line, compared to people who never caught COVID-19. (The study did not include cognitive test scores from before the patients caught COVID-19, which is another limitation of the research.)

The study included 46 people who received critical care for COVID-19 at Addenbrooke's Hospital in Cambridge, U.K., between March 10 and July 31, 2020; the patients ranged between 28 and 83 years old. Sixteen of these patients were placed on ventilators during their stays, and of these, 14 needed medical support for multiple failing organs. Researchers compared these 46 patients to 460 individuals of the same ages and demographics who hadn't previously caught COVID-19.   

All the participants completed eight cognitive tests via the Cognitron platform, a testing platform developed by Imperial College London. Overall, compared with the control group, the COVID-19 patients showed a "consistent pattern" of reduced accuracy and slowed processing time on the tests, although the degree of inaccuracy and slowness varied between tasks.

Compared with controls, the COVID-19 group showed the most significant deficits on verbal analogy tasks, where they were asked to complete analogies such as "'Up' is to 'Down' what 'Over' is to 'Under,'" for example. They also showed poorer accuracy and speed on a spatial task called "2D manipulation," in which they were asked to manipulate a 2D shape in their mind to solve a puzzle.

On average, the level of cognitive decline between the controls and the COVID-19 patients was "similar in scale to normal age-related decline in cognition between individuals in their 70s when compared to individuals in their 50s," the authors wrote in their report. The severity of this decline varied between individual patients depending on the severity of their initial infection, meaning it was worse among those who required ventilation and multiple organ support. 

The team did not find remarkable differences between patients tested six months out from their hospital stay and those tested 10 months out, although the 10-month group performed slightly better. "We conclude that any recovery in cognitive faculties is at best likely to be slow," the authors wrote. "It also is important to consider that trajectories of cognitive recovery may vary across individuals depending on illness severity and the neurological or psychological underpinnings, which are likely complex." 

These open questions will be tackled in future studies.

The researchers hope such studies will allow them to understand the mechanisms behind the cognitive decline, and perhaps prevent or treat it, study senior author David Menon, a professor at Cambridge University, told The Guardian (opens in new tab)

Originally published on Live Science.

Nicoletta Lanese
Staff Writer

Nicoletta Lanese is a staff writer for Live Science covering health and medicine, along with an assortment of biology, animal, environment and climate stories. She holds degrees in neuroscience and dance from the University of Florida and a graduate certificate in science communication from the University of California, Santa Cruz. Her work has appeared in The Scientist Magazine, Science News, The San Jose Mercury News and Mongabay, among other outlets.