Severe COVID results in cognitive impairment similar to that between the ages of 50 and 70 and is equivalent to losing ten IQ points, our latest research shows. The effects are still visible more than six months after the acute illness, and recovery is, at best, gradual.
There is growing evidence that COVID can cause permanent cognitive and mental problems, with recovering patients reporting symptoms including fatigue, “brain fog,” memory problems, sleep disorders, anxiety, and even post-traumatic stress disorder (PTSD) months after infections.
In the United Kingdom, a study found that approximately one in seven subjects reported symptoms involving cognitive impairment 12 weeks after a positive COVID test. And a recent brain imaging study found that even mild COVID can cause brain shrinkage. Only 15 of the 401 people in the study were hospitalized.
Random findings from the great British Intelligence Test project have also shown that mild cases can lead to persistent cognitive symptoms. However, these problems seem to increase with the severity of the disease. Indeed, it has been independently shown that between one-third and three-quarters of hospitalized patients report cognitive symptoms three to six months later.
The magnitude of these problems and the mechanisms responsible remain unclear. Even before the pandemic, it was known that a third of people who have an episode of the disease that requires admission to the ICU show objective cognitive deficits six months after admission.
This is thought to be due to an inflammatory response associated with critical illness, and the cognitive deficits observed in COVID could be a similar phenomenon. However, there is evidence that SARS-CoV-2, the virus that causes COVID, can infect brain cells. We cannot rule out a direct viral infection of the brain.
Other factors, such as hypoxia (low blood oxygen levels), may also play a role. It was also unclear whether widespread mental health problems reported after COVID were part of the same problem as objective cognitive deficits or represent a different phenomenon.
To characterize the type and magnitude of these cognitive deficits, and to better understand their relationship to acute disease severity and mental health problems at later time points, we analyzed data from 46 former COVID patients. All received hospital care, on a ward or JIL, for COVID at Addenbrooke Hospital in Cambridge, England.
Participants underwent detailed computerized cognitive tests an average of six months after acute illness using the Cognitron platform. This assessment platform is designed to accurately measure various aspects of mental abilities such as memory, attention, and reasoning and was used in the aforementioned study of civic science.
We also measured levels of anxiety, depression, and PTSD. The data of the study participants were compared with the corresponding controls – persons of the same sex, age and other demographic factors, but who were not hospitalized with COVID.
Survivors of COVID were less precise and slower to respond than appropriate controls. These deficits were slowly being addressed and could still be detected up to ten months after admission to the hospital. The effects increase with the severity of the acute illness and the markers of inflammation. They were the strongest for those who needed mechanical ventilation, but they were also important for those who were not.
Comparing patients with 66,008 members of the public, we were able to estimate that the magnitude of cognitive loss is on average similar to that occurring at 20 years of age, between 50 and 70 years of age. That’s the loss of ten IQ points.
Survivors have particularly poorly accomplished tasks such as “verbal analog thinking” (completing analogies such as shoelaces are what buttons for …). They also showed slower processing speeds, consistent with previous post-COVID observations of reduced brain glucose consumption in key areas of the brain responsible for attention, complex problem solving, and working memory.
While people who have recovered from severe COVID may have a wide range of symptoms of poor mental health – depression, anxiety, post-traumatic stress disorder, low motivation, fatigue, low mood and disturbed sleep – they are not associated with objective cognitive deficits, suggesting different mechanisms.
What are the causes?
Direct viral infection is possible, but it is unlikely to be the main cause. Instead, a combination of factors is more likely to contribute, including inadequate 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. Anecdotal evidence from first-line physicians supports this conclusion that some neurological problems may have become less common than the widespread use of corticosteroids and other drugs that suppress the inflammatory response.
Regardless of the mechanism, our findings have significant implications for public health. In England alone, around 40,000 people have undergone intensive care with COVID, and many more will be admitted to hospital. Many others may not have been in hospital despite a serious illness due to pressure on health care during the peak of the pandemic waves. This means that there are many people who still have problems with cognition many months later. We urgently need to look at what can be done to help these people. Studies are now underway to address this issue.
However, there is something of silver. If, as we suspect, the picture we see in COVID does indeed replicate the broader problem seen in other types of serious diseases, it provides an opportunity to understand the responsible mechanisms and research treatments.
This article was republished from The Conversation under a Creative Commons license. Read the original article.