Can COVID-19 cause long-term cognitive deficits?

COVID-19 can cause symptoms that last long after the viral infection has passed, sometimes referred to as post-COVID-19 syndrome or “long COVID” [1]. Can COVID-19 have long-term consequences on cognitive health? A large observational study in the UK reported that people who had recovered from COVID-19 experienced significant cognitive deficits, especially those who had been hospitalized [2]. But the deficits were also seen in people who had COVID-19 who had not been hospitalized.

Findings come from a large study of 81,337 people in the UK who completed a questionnaire and a series of cognitive tests as part of the Great British Intelligence Test, a collaborative citizen science project with BBC2 Horizon [2]. This study launched in December 2019 and was promoted as a way for people in the general public to find out what their greatest personal cognitive strengths were. But in May 2020, in response to the COVID-19 pandemic, the questionnaire was extended to include items pertaining to COVID-19 infection, symptom persistence and severity, common pre-existing medical conditions, and mood. Cognitive tests were administered via an online assessment platform and included nine tests that measured planning/reasoning, memory, attention, and emotion processing abilities [3].

The study found that people who had recovered from COVID-19, including those no longer experiencing symptoms, showed cognitive deficits when compared to those who had not gotten COVID-19. These deficits were evident even after controlling for many factors such as age, gender, educational level, income, race/ethnicity, pre-existing medical conditions, tiredness, depression, and anxiety. People who had been hospitalized and put on a ventilator had the greatest deficit in cognitive function, followed by people who had been hospitalized but were not put on a ventilator. People who were put on a ventilator showed cognitive deficits equivalent to a ten-year decline in cognitive function or a seven-point difference in a classic IQ test. In people who were not hospitalized but experienced breathing problems, those who required medical assistance at home had greater cognitive deficit than those who did not. Even those who had COVID-19 without breathing problems, small deficits in cognitive functions were seen when compared to those who had not gotten COVID-19. Overall, COVID-19 was associated with greater deficits in complex tasks requiring reasoning, planning, and problem solving, while sparing simpler functions such as memory and emotional processing.

This study identified a relationship between COVID-19 infection and cognitive deficits, but it was not designed to determine the biological mechanism underlying the cognitive deficit associated with COVID-19. There are many unanswered questions—do people who have asymptomatic COVID-19 also suffer from this cognitive deficit? What are the conditions that make people more vulnerable to cognitive deficit after COVID-19? How long does the cognitive deficit persist—does it go away after some time?

More research is needed to understand the long-term effects of COVID-19 and to develop new treatments to alleviate these symptoms. In the meantime, the best way to protect yourself from COVID-19 and its long-term effects is to prevent COVID-19 illness by receiving one of the approved vaccines for COVID-19 [1]. If COVID-19 is spreading in your community, stay safe by following local guidance and taking precautions, like wearing a mask, physical distancing, and cleaning your hands.

1. (2021) Post-COVID Conditions.
2. Hampshire A, Trender W, Chamberlain SR et al. (2021) Cognitive deficits in people who have recovered from COVID-19. EClinicalMedicine 39, 101044.
3. (2019) Great British Intelligence Test.

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