There is growing evidence that COVID can cause lasting cognitive and mental health problems, with patients recovering from symptoms such as fatigue, “brain fog,” memory problems, sleep disorders, anxiety, and even sleep disorders. post-traumatic stress disorder (PTSD) months after infection.
In the UK, one study found that around one in seven people surveyed reported having symptoms that included cognitive difficulties 12 weeks after a positive COVID test. And a recent brain imaging study found that even mild COVID can cause the brain to shrink. Only 15 of the 401 people in the study had been hospitalized.
Incidental findings from a major citizen science project (the Great British Intelligence Test) also showed that mild cases can cause persistent cognitive symptoms. However, these problems seem to increase with the severity of the disease. In fact, it has been independently shown that between one-third and one-third of hospitalized patients report cognitive symptoms three to six months later.
The magnitude of these problems, and the mechanisms that are responsible for them, are still unclear. Even before the pandemic, it was known that one-third of people with an episode of illness that requires admission to the ICU have objective cognitive deficits six months after admission.
This is thought to be a consequence of the 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 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 the widespread psychological health problems reported after COVID were part of the same problem as the objective cognitive deficits or represented a different phenomenon.
To characterize the type and magnitude of these cognitive deficits and to better understand their relationship to the severity of the disease in the acute phase and psychological health problems at later times, we analyzed data from 46 former patients with COVID. All had received hospital care, in the ward or ICU, by COVID at Addenbrooke Hospital in Cambridge, England.
Participants underwent detailed computerized cognitive testing an average of six months after their acute illness using the Cognitron platform. This assessment platform is designed to accurately measure different aspects of mental faculties such as memory, attention, and reasoning and had been used in the aforementioned citizen science study.
We also measured levels of anxiety, depression, and PTSD. Data from study participants were compared with matching controls: people of the same sex, age, and other demographic factors, but who were not hospitalized with COVID.
COVID survivors were less accurate and reacted slower than matching controls. These deficits were slowly resolved and were still detected up to ten months after hospitalization. The effects escalated with the severity of the acute illness and the markers of inflammation. They were stronger for those who needed mechanical ventilation, but they were also substantial for those who did not.
When comparing patients with 66,008 people, we were able to estimate that the magnitude of cognitive loss is similar, on average, to that maintained at 20 years of age, between 50 and 70 years. This equates to losing ten IQ points.
Survivors scored especially low on tasks such as “verbal analogical reasoning” (completing analogies such as laces are on shoes what buttons are on …). They also showed slower processing speeds, which align with previous post-COVID observations of decreased brain glucose consumption in key areas of the brain responsible for attention, complex problem solving, and working memory.
Although people who have recovered from severe COVID may have a wide range of symptoms of poor mental health (depression, anxiety, post-traumatic stress, low motivation, fatigue, low mood, and sleep disorders), these were not related to objective cognitive deficits, proposing different mechanisms.
What are the causes?
Direct viral infection is possible, but is unlikely to be a major cause. In contrast, a combination of factors, such as inadequate oxygen or blood supply to the brain, clogging of large or small blood vessels due to clotting, and microscopic bleeding, are more likely to contribute.
However, emerging evidence suggests that the most important mechanism may be the damage caused by the inflammatory response of the body and the immune system. Anecdotal evidence from primary care physicians supports this inference that some neurological problems may have become less common since the widespread use of corticosteroids and other drugs that suppress the inflammatory response.
Regardless of the mechanism, our findings have substantial public health implications. About 40,000 people have undergone intensive care with COVID in England alone, and many more will have been admitted to hospital. Many others may not have received hospital treatment despite serious illness due to pressure on health care during peak pandemic waves. This means that there are many people who still have cognition problems 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 some silver lining. If, as we suspect, the image we see in COVID in fact replicates the broader problem seen in other types of serious illness, this offers an opportunity to understand the mechanisms responsible and explore treatments.
This article is republished from The Conversation under a Creative Commons license. Read the original article.