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New study shows just how common long-term cognitive impairment is for some COVID patients

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More than 70% of severely ill COVID patients experience delirium while they’re hospitalized - but a significant number of them are still struggling with significant mental impairment long after they’ve returned home, bewildering family members and making patients themselves “feel crazy.”

Nearly 1 in 4 COVID patients who experienced delirium in the ICU were still experiencing it months after being discharged from the hospital, a new study from the University of Michigan finds. Almost as many experienced “cognitive impairment consistent with dementia,” and 12% screened positive for depression.

“That's a form of suffering that makes these people feel crazy, isolated and not themselves anymore,” Dr. Wes Ely, professor of medicine at Vanderbilt University and co-director of the Center for Critical Illness, Brain Dysfunction, and Survivorship, when asked to comment on the study from an outside perspective.

“And it dehumanizes them if they are not validated and seen. And so I think that the value of the study is the confirmation that the brain fog is still going. That is part of long covid. And that it drives us all to say [to long haulers] ‘I see you, and I know you're having problems and we're sorry. And if you can't do your job, you're not making that up. That’s real.’”

Why do so many COVID patients experience delirium?

At the beginning of the pandemic, a doctor in Barcelona was diagnosed with COVID-19. He was hospitalized, and eventually had to be intubated. While he eventually recovered, his memories of that time - and the delirium he experienced - were published inFrontiers in Psychiatry.

Delirium, he wrote, was like “a barrage of dreams and nightmares that I lived with an intensity that I never experienced before:”

“That dying man, without movement, with hardly any response to stimuli, had a cerebral life, like he never had before. In my other life, I did not get COVID 19 in Barcelona, I got sick on a trip to Miami, where I stayed with Ukrainian refugees. I was not hospitalized in Barcelona, I was in Miami, Mallorca, and in Tarragona. I travelled all over Europe and the United States. I resided in spas, luxury hotels, apartments, hospitals, clinics, psychiatric units, and drug addiction centers. I was buried alive in the grave of an uncle of mine who died ten years ago, I drowned in a pool that the hospital nurses threw me into. I remember perfectly and clearly the feeling of lack of air... 

“...The most curious thing about all that delirious time is the tremendously clear memories that I have of dreams, that I lived as if they were reality, compared to the null memory of reality, which for me was like a dream.”

Delirium, defined as a significant disruption of a person’s memory and ability to think, can include hallucinations, personality changes, agitation and even aggression. And it’s remarkably common among hospitalized COVID patients: researchers found 73% of those in the ICU experienced it, a frequency backed by other studies as well.

That’s probably due to several factors, said Dr. Phil Vlisides, an anesthesiology professor at the University of Michigan medical school and senior author of the new study. For one, there are the effects of sedation medication that’s often used for these patients. Then there’s the fact that with visitation restrictions, they can’t give COVID patients the kind of treatments they typically use for delirium, like bringing in family members or familiar objects from home.

Then, of course, there’s the coronavirus itself.

“We know that the virus...can sometimes invade the brain, and directly cause brain inflammation and brain damage,” Vlisides said. “We know that the body's inflammatory response to the infection can be really pronounced, and can also cause inflammation in the brain.

“We also know that, unfortunately, patients with COVID are at increased risk of stroke. They're at increased risk of having really low oxygen levels throughout the body with severe disease. And that can cause what's called ischemic injury in the brain [which is when the brain doesn’t get enough blood flow.] And so there are all these different causes that can likely contribute to delirium.”

Months after coming home, many patients still delirious, mentally impaired

Through phone screenings, Vlisides and his team checked in with patients 1 and 2 months after they’d been discharged. Some 24% still screened positive for delirium. And 23% had “questionable cognitive impairment or cognitive impairment consistent with dementia.” About 12% screened positive for depression.

“A number of family members said that ‘My loved one is still often confused, or doesn't quite have the attention that he or she used to, or they're sleeping a lot more,’” he said. “So I think the point is for some of these patients who are admitted to the ICU, who are lucky enough to get through the ICU and get home, they're not out of the woods yet.”

Researchers have known for months that COVID carries an increased risk of developing psychiatric illnesses, like anxiety and depression. But solidifying the link between what happens to the body and brain initially during COVID (the delirium, the inflammation, the immune response) to long-term cognitive impairment is crucial, Ely said.

“That really advances what we learned in [prior studies] in a beautiful way, because it says, wait a minute: this brain problem, it's still going on. And it's still going on weeks and months later.”

“..[T]he findings of a prolonged duration of delirium and cognitive decline is important,” said Dr. Sharon. K. Inouye, professor of medicine at Harvard Medical School and Director, Aging Brain Center, Marcus Institute for Aging Research, Hebrew SeniorLife.

“There were substantial losses to follow-up, but this is certainly an important exploratory finding worthy of future confirmation. The study also helps to shed light on some important delirium risk factors and potential pathophysiologic mechanisms such as inflammation.”

A “very real risk” to mental health 

At this point in the pandemic, with 56% of the US population and 52% of Michiganders vaccinated, people need to understand the real risk, Vlisides said. And studies like this show that just focusing on your chance of surviving COVID, doesn’t provide the full picture.

“If you get COVID and...even if you don’t end up in the ICU, there is that risk of long term complications, where there’s a real risk of not getting back to your regular baseline day-to-day lifestyle before having COVID,” he said. “We hear so often in the news about mortality rates...but even if you get COVID and you’re lucky enough to survive...it’s not just this binary distinction of whether you may or may not die... There is still a very real risk to both mental health and physical health for weeks and months or longer to come.”

For long haulers already struggling with these symptoms, this could provide some additional validation that their experiences are real, said Ely.

“You’re not making that up,” he said. “And we need to make accommodations for you. We need to get you into cognitive rehab. We need to do everything we can to get you back on track in life.”

Kate Wells is a Peabody Award-winning journalist currently covering public health. She was a 2023 Pulitzer Prize finalist for her abortion coverage.
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