Summary: Severe COVID-19 infection results in cognitive impairment similar to that experienced by natural aging between the ages of 50 and 70, and is equivalent to losing 10 IQ points.
Source: University of Cambridge
The cognitive impairment resulting from severe COVID-19 is similar to that experienced between the ages of 50 and 70 and is equivalent to losing 10 IQ points, according to a team of scientists from the University of Cambridge and Imperial College London.
The results, published in the journal eClinicalMedicine, emerging from the NIHR COVID-19 BioResource. The study results suggest that the effects are still detectable more than six months after the acute illness, and that any recovery is gradual at best.
There is growing evidence that COVID-19 can cause long-lasting cognitive and mental health problems, with recovered patients reporting symptoms including fatigue, ‘brain fog’, problems recalling words, trouble sleeping, anxiety and even post-traumatic stress disorder (PTSD) months after infection. In the UK, a study found that around one in seven respondents said they had symptoms including cognitive difficulties 12 weeks after testing positive for COVID-19.
While even mild cases can lead to persistent cognitive symptoms, between one-third and three-quarters of hospitalized patients still report experiencing cognitive symptoms three to six months later.
To explore this link in more detail, the researchers analyzed data from 46 people who received hospital care, either in the ward or intensive care unit, for COVID-19 at Addenbrooke Hospital, part of the Cambridge University Hospitals NHS Foundation Trust. 16 patients were placed on mechanical ventilation during their hospital stay. All patients were admitted between March and July 2020 and were recruited from the NIHR COVID-19 BioResource.
Individuals underwent detailed computerized cognitive testing an average of six months after their acute illness using the Cognitron platform, which measures different aspects of mental faculties such as memory, attention and reasoning. Scales measuring anxiety, depression and post-traumatic stress disorder were also assessed. Their data was compared to matched controls.
This is the first time that such a rigorous evaluation and comparison has been carried out with regard to the sequelae of severe COVID-19.
COVID-19 survivors were less accurate and with slower response times than the matched control population — and these deficits were still detectable when patients followed up six months later.
The effects were strongest for those who required mechanical ventilation. Comparing the patients to 66,008 members of the general public, the researchers estimate that the magnitude of cognitive loss is similar on average to that experienced with 20 years of aging, between 50 and 70, and that this is equivalent to losing 10 IQs. points.
Survivors performed particularly poorly on tasks such as verbal analogical reasoning, a finding that supports the commonly reported problem of difficulty finding words. They also showed slower processing speeds, consistent with previous post COVID-19 observations of decreased cerebral glucose uptake in the brain’s frontoparietal network, responsible for attention, complex problem solving, and working memory, among other functions.
Professor David Menon from the University of Cambridge’s Division of Anaesthesia, lead author of the study, said: “Cognitive impairment is common to a wide range of neurological disorders, including dementia, and even routine aging, but the patterns we observed — the “fingerprint” cognitive impairments of COVID-19 — were distinct from all of that.
Although it is now well established that people who have recovered from serious illness related to COVID-19 can experience a wide range of symptoms of poor mental health – depression, anxiety, post-traumatic stress, low motivation, fatigue , moodiness and disturbed sleep – the team found that the severity of acute illness was better at predicting cognitive deficits.
Patients’ scores and reaction times began to improve over time, but the researchers say any cognitive recovery was gradual at best and likely to be influenced by a number of factors, including the severity of the disease and its neurological or psychological impacts.
Professor Menon added: ‘We followed some patients up to ten months after their acute infection, so we could see very slow improvement. Although this is not statistically significant, it is at least going in the right direction, but it is very possible that some of these people will never fully recover.
According to the researchers, several factors could be at the origin of the cognitive deficits. Direct viral infection is possible, but unlikely to be a major cause; instead, it is more likely that a combination of factors is contributing, including insufficient oxygen or blood supply to the brain, blockage of large or small blood vessels due to clotting, and microscopic bleeding. However, new evidence suggests that the most important mechanism may be damage caused by the body’s inflammatory response and immune system.
Although this study looked at hospitalized cases, the team says that even patients who are not sick enough to be admitted may also have telltale signs of mild impairment.
Professor Adam Hampshire from the Department of Brain Sciences at Imperial College London, first author of the study, said: ‘Around 40,000 people have been in intensive care with COVID-19 in England alone and many more Others will have been very ill, but not admitted to hospital. This means that a large number of people still experience problems with cognition several months later. We urgently need to consider what can be done to help these people.
Professor Menon and Professor Ed Bullmore from Cambridge’s Department of Psychiatry co-lead working groups in the COVID-19 Neuroscience Clinical Study (COVID-CNS) which aim to identify biomarkers linked to neurological impairments resulting from COVID-19, and associated neuroimaging changes.
Funding: The research was funded by NIHR BioResource, NIHR Cambridge Biomedical Research Center and Addenbrooke’s Charitable Trust.
About this research update on cognition, aging and COVID-19
Original research: Free access.
“Multivariate profile and acute phase correlates of cognitive deficits in a hospitalized COVID-19 cohort” by Hampshire, A et al. eClinicalMedicine
Multivariate profile and acute phase correlates of cognitive deficits in a hospitalized COVID-19 cohort
Preliminary evidence has pointed to a possible association between severe COVID-19 and persistent cognitive deficits. Further research is needed to confirm this association, to determine whether cognitive deficits are related to clinical features of the acute phase or to mental health status at the time of assessment, and to quantify the rate of recovery.
46 people who received intensive care for COVID-19 at Addenbrooke’s Hospital between March 10, 2020 and July 31, 2020 (16 on mechanical ventilation) underwent a detailed computerized cognitive assessment as well as scales measuring anxiety , depression, and post-traumatic stress disorder under supervised conditions at a mean follow-up of 6.0 (± 2.1) months after acute illness.
Patient and matched control (NOT = 460) performance was transformed into standard deviation from expected scores, taking into account age and demographic factors using NOT = 66,008 normative data sets. Overall accuracy and response time composites were calculated (G_SScore & G_RT). Linear modeling predicted deficits in composite scores of acute acuity, mental health status at assessment, and time since hospital admission.
The pattern of deficits between tasks was qualitatively compared to normal age-related decline and early-stage dementia.
COVID-19 survivors were less accurate (G_SScore=-0.53SD) and slower (G_RT=+0.89SD) in their responses than expected compared to their matched controls. Acute illness, but not chronic mental health, significantly predicted cognitive deviation from expected scores (G_SScore (p=0.0037) and G_RT (p = 0.0366)).
The strongest task associations with COVID-19 were for higher cognition and processing speed, which were qualitatively distinct from normal aging and dementia profiles and similar in magnitude to the effects of aging between 50 and 70 years. A trend of decreasing deficits with time since illness (r∼=0.15) did not reach statistical significance.
Cognitive deficits after severe COVID-19 are more strongly related to acute disease severity, persist long into the chronic phase, and recover slowly, if at all, with a characteristic profile highlighting cognitive function and speed. higher treatment.
This work was funded by the Cambridge Biomedical Research Center (BRC) of the National Institute for Health Research (NIHR), the NIHR Cambridge Clinical Research Facility (BRC-1215-20014), Addenbrooke’s Charities Trust, and the NIHR COVID-19 BioResource RG9402. AH is funded by the UK Dementia Research Institute Care Research and Technology Center and Imperial College London Biomedical Research Centre. ETB and DKM are supported by NIHR Principal Investigator Awards. JBR is supported by the Wellcome Trust (220258) and the Medical Research Council (SUAG/051 G101400). The VFJN is funded by a Clinician Fellowship from the Academy of Medical Sciences/The Health Foundation. The views expressed are those of the authors and not necessarily those of the NHS, NIHR or Department of Health and Social Care.