The most comprehensive 'long COVID' study to date finds that cognitive decline associated with some cases of COVID-19 appears to be equivalent to losing 10 IQ points.
Two years into the pandemic, researchers are still figuring out what’s going on inside the heads of COVID-19 survivors. From brain fog, to neurologically linked sensory issues like loss of taste or smell, to sleep disturbances, anxiety, post-traumatic stress disorder (PTSD), to sudden strokes or lasting delirium, people have reported a range of neuropsychiatric symptoms linked to infection with the SARS-CoV-2 virus.
In “long-haul” patients, these symptoms persist for months. The relationship between this virus and and the onset of dementia or Alzheimer’s is not yet known — and researchers will need years more to understand any relationship there in full — but, evidence is growing that the diseases do share the biomarkers of brain damage. Now, a new study has found that the lasting impacts from COVID-19 on cognitive function — i.e. memory, attention, or problem solving — can result in cognitive impairment equivalent to suddenly aging 20 years.
The cognitive effects of the disease, the researchers say, are the equivalent of losing 10 IQ points.
The research, published in the journal eClinicalMedicine, was led by a team of scientists from the University of Cambridge and Imperial College London, who say that this is the first time that such rigorous assessment has been done on the after-effects of severe infection.
Their findings indicate that the degradation of cognitive function following COVID-19 was comparable to the cognitive decline typically experienced by people between age 50 and 70. The team also found that the effects are still detectable more than six months after acute illness — prolonged onset known as “long COVID” — and that any recovery is gradual, at best.
“Tens of thousands of people have been through intensive care with COVID-19 in England alone and many more will have been very sick, but not admitted to hospital,” Professor Adam Hampshire from the Department of Brain Sciences at Imperial College London and first author of the study said in a news release. “This means there are a large number of people out there still experiencing problems with cognition many months later. We urgently need to look at what can be done to help these people.”
Studying the cognitive effects of COVID, six months out
Researchers analyzed data from 46 people who received in-hospital or ICU care for COVID-19, 16 of whom were put on mechanical ventilation during their stay in hospital. All of the patients were admitted to Addenbrooke’s Hospital in Cambridge, England between March 2020 and July 2020.
These patients took cognitive tests an average of six months after their illness, measuring aspects of cognitive function including memory, attention and reasoning, as well as anxiety, depression and post-traumatic stress disorder. The resulting data was compared to matched controls.
While this study looked at hospitalized cases, the researchers note that even those who were never admitted to a hospital may have tell-tale signs of mild cognitive impairment.
The data shows that COVID-19 survivors were had slower response times and less accurate memory recall than the control group — a gap that persisted six months after infection. The more severe the infection, researchers noted from comparing those who were put on ventilators to other individuals, the more severe the subsequent follow-up impairment.
With COVID-19, aging 20 years ‘overnight’
Comparing the patients to 66,008 members of the general public, the team estimates that the magnitude of cognitive loss is similar on average to that sustained with 20 years aging, between 50 and 70 years of age, and that this is equivalent to losing 10 IQ points.
COVID-19 survivors scored especially poorly on tasks like verbal analogical reasoning (difficulty finding words), and they showed slower processing speeds. These track with previous observations of COVID-19 survivors.
“Cognitive impairment is common to a wide range of neurological disorders, including dementia, and even routine aging, but the patterns we saw – the cognitive ‘fingerprint’ of COVID-19 – was distinct from all of these,” study senior author Professor David Menon from the Division of Anaesthesia at the University of Cambridge said in the news release.
Gradual recovery ‘at best’ following COVID-19
Patients’ scores and reaction times improved over time, the researchers said, but any recovery in cognitive function was gradual.
“We followed some patients up as late as ten months after their acute infection, so were able to see a very slow improvement,” Menon said. “While this was not statistically significant, it is at least heading in the right direction, but it is very possible that some of these individuals will never fully recover.”
A separate study in the UK found that around one in seven individuals surveyed reported having symptoms that included cognitive difficulties 12 weeks after a positive COVID-19 test. Between a third and three-quarters of hospitalized patients report still suffering cognitive symptoms three to six months later.