COVID-19 survivors shows evidence of ‘long COVID’ cognitive deficits

Neurodegenerative disorders

By Michael Woodhead

29 Jul 2021

Evidence from a large cohort of UK patients who had COVID-19 supports the hypothesis that SARS-CoV-2 infection is associated with cognitive deficits that persist into the recovery phase.

The findings come from series of cognitive assessments that were already underway for more than 80,000 individuals  when the COVID-19 pandemic started in early 2020.

Cognitive performance data were assessed between January and December 2020  in a cross section of 81,337 members of the public who were invited to take part in a BBC television science project on national intelligence levels that was launched in December 2019.

Participants were asked to complete nine clinically-validate cognitive tests online. At the start of the study, participants were not asked specifically about COVID-related symptoms or diagnosis. However as the pandemic progressed, study investigators followed up with a series of additional questions to participants pertaining to the impact of the pandemic, including suspected or confirmed COVID-19 illness, alongside details of symptom persistence and severity, relevant pre-existing medical conditions, and measures of depression, anxiety and post-traumatic stress.

After they collated the results , the investigators found that people who had recovered from COVID-19, including those no longer reporting symptoms, exhibited significant cognitive deficits versus controls after controlling for age, gender, education level, income, racial-ethnic group, pre-existing medical disorders, tiredness, depression and anxiety.

The cognitive deficits were substantial for 192 subjects who had been hospitalised (N = 192) with COVID-19. However  cognitive deficits were also significant for 326 non-hospitalised individuals who had biological confirmation of COVID-19 infection.

“The scale of the observed deficit was not insubstantial; the 0.47 SD global composite score reduction for the hospitalised with ventilator sub-group was greater than the average 10-year decline in global performance between the ages of 20 to 70 within this dataset,” the study authors wrote in Lancet EClinicalMedicine.

“It was larger than the mean deficit of 480 people who indicated they had previously suffered a stroke (−0.24SDs) and the 998 who reported learning disabilities (−0.38SDs). For comparison, in a classic intelligence test, 0.47 SDs equates to a 7-point difference in IQ.”

By comparison, deficits for COVID-19 infected people who were not hospitalised were -0.23SDs managed at home for respiratory difficulty and  −0.07 SDs  for those with no medical assistance but respiratory difficulty.

The authors noted that the deficits were most pronounced in assessments of cognitive functions such as reasoning, problem solving, spatial planning and target detection whilst sparing tests of simpler functions such as working-memory span as well as emotional processing.

“These results accord with reports of long-COVID, where ‘brain fog’, trouble concentrating and difficulty finding the correct words are common,” they said.

The investigators said the deficits may represent the effects of hypoxia or neurological damage from COVID-19 disease, and suggested the tests used in their study be adopted for monitoring of cognitive function among other groups of COVID-19 patients during recovery.

“Multiple studies are now using the online assessment technology reported here to investigate the neural correlates of cognitive deficits in people who have survived SARS-COV-2 infection, relate them to clinical outcomes and track at scale how they change over time,” they said.

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