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expert reaction to study looking at measures of cognitive performance in people who had and hadn’t had Covid

A study published in NEJM looks at cognition and memory after Covid-19. 


Dr Michael Zandi, neurologist and researcher at UCL’s Queen Square Institute of Neurology, and Consultant Neurologist at the National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Foundation Trust (UCLH), said:

“This is a large-scale on-line study of over 100,000 individuals, with some caveats, e.g. ascertainment bias and the nature of dealing with computer testing.  This study aligns findings in hospitalised and non-hospitalised individuals and points to concussion-like mechanisms of attention as the main deficit, with some reassuring data against damage to memory storage parts of the brain.  The biological mechanisms underlying these findings are likely multiple, remain unclear and deserve detailed longitudinal study and therapeutic trials.”


Dr Maxime Taquet, NIHR Academic Clinical Fellow in Psychiatry, University of Oxford, said:

“Cognitive deficits in people who had COVID-19 is an important public health problem.  But the magnitude of cognitive problems experienced by patients remained largely unknown.  By using an innovative cognitive test which has also been completed by people who did not have COVID-19, this important and well-conducted study provides the first accurate quantification of the scale of cognitive deficits in people who had COVID-19.  They found a small but clear association of COVID-19 with cognition.  This is more obvious at the extremes: the risk of having more severe cognitive problems was almost twice as high in those who had COVID-19 compared to those who did not, and three times as high in those who were hospitalised with COVID-19.  A few key questions remain open: Do these cognitive problems persist or improve in the years after infection? What is their biological explanation? How does it affect people’s everyday life and their ability to work?


Is this good quality research?  Are the conclusions backed up by solid data?



Have the authors accounted for confounders?  Are there important limitations to be aware of?

“Yes.  The main limitation is that many invited people did not complete the test and therefore the population might not be representative of the general population.


What are the implications in the real world?  Is there any overspeculation?

“Even if cognitive deficits after COVID-19 are of small magnitude on average, a substantial minority of people have more significant deficits which are likely to affect their ability to work and function.  Given the scale of the pandemic and the number of people affected, this is particularly worrisome.


Have the authors measured a change in cognitive score in individuals, or is it a single timepoint measurement which is being compared across different groups?

“This is a timepoint measurement compared across different groups.


Do we know what might be behind these differences, or is it impossible to say from this study?

“It is impossible to know what might be the underlying mechanisms.”


Prof Claire Steves, Professor of Ageing and Health, and Dr Nathan Cheetham, Senior Postdoctoral Data Scientist at King’s College London, said:

“This study finds the same key results as previous work looking at the effects of COVID-19 on cognition, but in a larger sample of participants.  In particular, it was important to note that people whose symptoms have resolved performed better on tests compared to those with unresolved, ongoing symptoms.  This reiterates the need to understand what helps people to recover, in terms of immediate social and health care support as well as understanding the underlying biology to develop medical treatment.

“The participants most affected by COVID-19 saw deficits in tasks focused on memory, reasoning, and executive function, which for many affects their ability to perform daily activities like work and caring for others.  Thus, reasonable adjustments from employers, and understanding and support from family and friends, remains crucial for those who continue to live with the effects of COVID-19.”



‘Cognition and Memory after Covid-19 in a Large Community Sample’ by A. Hampshire et al. was published in the New England Journal of Medicine at 22:00 UK time on Wednesday 28 February 2024.


DOI: 10.1056/NEJMoa2311330



Declared interests

Dr Michael Zandi: “MZ is part of the UCL Stimulate ICP long covid study and sees patients with neurological symptoms post covid at Queen Square, and has had funding from the National Brain Appeal Charity.  MZ is also involved in the UKRI funded COVIDCNS study.  No other relevant declarations.”

Dr Maxime Taquet: “I have no conflict of interest to disclose.”

For all other experts, no reply to our request for DOIs was received.


This SMC Roundup was accompanied by an SMC Briefing.

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