Risk of ‘brain fog’ remains high two years after Covid, study finds

AAmong the many worrying consequences of Covid-19, neuropsychiatric conditions occupy a prominent place. A year ago, researchers at the University of Oxford reported that one in three patients suffered from mood disorders, strokes or dementia six months after Covid infection. Now the same group is back with a longer-term analysis of 1.25 million Covid patient records, including what they believe is the first large-scale look at children and new variants.

Their news is both bad and good.

Up to two years after infection with Covid-19, the risk of developing conditions such as psychosis, dementia, “brain fog” and seizures is still higher than after other respiratory infections, report the researchers in their study published Wednesday in the Lancet Psychiatry. But while anxiety and depression are more common soon after a Covid-19 diagnosis, mood disturbances are transient, becoming no more likely after the two months than following similar infections such as influenza.


The children were no more likely to be diagnosed with anxiety or depression, immediately or up to two years after Covid, and their risk of brain fog subsided within two years. But they were still more likely than children recovering from other respiratory infections to have seizures and psychotic disorders. Overall, the likelihood of all of these diagnoses was lower in children than in adults.

On the variants, the risk of neuropsychiatric diagnoses increased from 10% higher for anxiety to 38% higher for brain fog – after the Delta variant appeared than after the alpha version. Similar risks persisted with Omicron, although this variant has milder effects during the acute phase of infection.


“What these data show in this very large cohort analyzed retrospectively is that the mood disorders and anxiety issues that are really, really prevalent in long Covid tended to resolve within a few months, which which is great news for long covid patients who are not. used to suffering in this way,” Wes Ely, a critical care physician at Vanderbilt University Medical Center and associate director of research for the VA Tennessee Valley Geriatric Research and Education Clinical Center, told STAT. He did not participate in Oxford studies.

“The other finding from this fascinating investigation is that the cognitive issues, the neurocognitive deficits that cause people to have brain fog, don’t resolve as quickly,” he said. “Clinically, in my own practice and in our long Covid clinic, that’s exactly what we’re seeing: that the acquired dementia that these patients get tends to be long-lasting and very problematic.”

To reach their conclusions, the Oxford team combed through data from 14 neurological and psychiatric diagnoses captured in electronic health records from the TriNetX network, mostly from the United States, over a two-year period. For a control group, the 1.25 million Covid patients were matched with an equal number of patients with any other respiratory infection and no history of Covid. Compared to people in the control group:

  • Adults under 65 with a history of Covid infection up to two years previously had a higher risk of cognitive impairment, better known as brain fog (640 versus 550 cases per 10,000 people) and muscle disease (44 versus 32 cases per 10,000 people). ).
  • Adults 65 and older who had Covid during the same period had more diagnoses of brain fog (1,540 vs. 1,230 per 10,000 people), dementia (450 vs. 330 per 10,000 people) and psychotic disorder (85 versus 60 per 10,000 people). ).
  • Children who had Covid were more likely to have seizures (260 versus 130 cases per 10,000 children) and psychotic disorders (18 versus 6 per 10,000 children).

Max Taquet, an academic clinical researcher in psychiatry at the National Institute for Health and Care Research in Oxford and co-author of the study, pointed out that the high risk of seizures and psychotic disorders in children was still low. “It’s important to keep in mind that the absolute numbers are often very small, much smaller than in adults,” he said on a call with reporters.

Taquet made the same point about adults. “I think it’s very clear that this is not a tsunami of new dementia cases,” he said. “Equally, I think it’s hard to ignore, given the severity of the consequences of dementia diagnoses. A 1.2% increase in the population in absolute terms and compared to other previous infections is hard to ignore.

Paul Harrison, professor of psychiatry at Oxford and co-author of the study, said those numbers were still significant. “Certainly for some conditions, there seems to be a non-trivial and persistent increased risk of these diagnoses being made,” he said on the call with reporters. “And for some of those diagnoses, it’s very likely that those people will need medical attention.”

Until the mechanisms of long Covid – and any potential treatment – ​​are understood, “what is important to me as a doctor is that we know that we can have long-term results in persistent neuropsychiatric disorders and very severe disabling,” some that can be treated, said Teodor Postolache, professor of psychiatry at the University of Maryland School of Medicine.

An editorial published with the journal warns against psychiatric diagnoses.

“Dementia has an insidious onset, and the cohort likely had participants with undiagnosed or subclinical cases at baseline,” write Jonathan Rogers and Glyn Lewis of University College London. “While concerning, the findings for psychosis and dementia need to be replicated in a cohort in which there is further determination of case status.”

Electronic health records have limitations in how they reveal complicated neuropsychiatric conditions – which could mean they are underreported, another longtime Covid researcher has said. “I can tell you for sure that it’s really hard to express in medical records, especially if you’re busy doing a lot, all the nuances that go along with neurocognitive issues,” said Steven Deeks, teacher. of medicine at the University of California, San Francisco, told STAT. “This stuff can be subtle. It just picks up some very direct stuff. Ultimately, this provides further evidence that long Covid is real, that some people may have profound symptoms, and that they may persist for a few years.

Rachel Sumner, senior researcher at Cardiff Metropolitan University, called the study’s findings “alarming” as Covid continues to spread. “The discovery of complex and potentially serious psychiatric and neurological fallout from Covid infection adds even more weight and concern to the impact of repeat infections that will occur if the virus continues to spread to reinfect itself with little or no control,” she said in a statement.

The study did not explore the causes of neuropsychiatric illnesses, but Ely de Vanderbilt said the prevalence it reports aligns with emerging research on different parts of the brain affected by the SARS-CoV-2 virus, corresponding mood and cognitive disorders. deficiency. And he worries about what will happen next.

“This paper…fits both what I’m seeing clinically in practice, but also the actual brain science that we’re running into,” he said. Regarding dementia, he said: “It’s something that’s very difficult for people to deal with because they can’t go back to work. They need to retire early and they desperately need answers.