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Cognition was impaired for at least a year and a half after severe SARS-CoV-2 infection, but overall cognitive problems were like those seen in patients hospitalized for other severe diseases, a prospective study showed.

Compared with healthy controls, people hospitalized for COVID-19 had significantly worse long-term overall cognition, measured by the Screen for Cognitive Impairment in Psychiatry (SCIP) and the Montreal Cognitive Assessment (MoCA), according to Michael Eriksen Benros, MD, PhD, of Copenhagen University Hospital in Denmark, and co-authors.

But compared with people hospitalized for other severe illness -- pneumonia, myocardial infarction, or other conditions requiring intensive care -- scores on the SCIP (P=0.12) and the MoCA (P=0.07) at 18-month follow-up were similar, the researchers reported in .

Patients hospitalized with COVID-19 also performed like other seriously ill patients on most other long-term psychiatric and neurological tests, except they had worse executive function scores.

Long-term links between COVID and cognition might not be specific to SARS-CoV-2 but associated more with overall illness severity and hospitalization, Benros noted.

"Our study shows that individuals with COVID-19 requiring hospitalization were more affected on their brain health regarding neurological, cognitive, and psychiatric symptoms than matched healthy controls," he wrote in an email to MedPage Today. "However, when comparing COVID-19 patients to non-COVID-19 patients matched on similar disease severity -- due to, for instance, other non-COVID infections -- both groups were comparably affected."

Previous research showed that 10.7% of hospitalized patients discharged after severe SARS-CoV-2 infection in Brazil had long-term impairment that persisted for 1 year. And among COVID-19 survivors discharged from Wuhan hospitals in early 2020, the incidence of cognitive impairment 12 months later was 12.45%. But other research suggested long-term neurocognitive dysfunction might be more pervasive, with one study showing that for COVID may have at least one cognitive domain affected.

"Clinical studies with long-term follow-up comparing sequelae after COVID-19 to sequelae after other severe medical conditions have been vastly lacking," Benros observed.

The researchers enrolled 120 hospitalized COVID patients at two Copenhagen hospitals from March 2020 through March 2021, matching them with 100 healthy controls and 125 hospitalized controls. Hospitalized controls were admitted for non-COVID pneumonia (50 people), myocardial infarction (50 people), or non-COVID intensive care (25 people). People with pre-existing cognitive impairment were excluded from the study.

Hospitalized COVID patients were about 61 years old on average, and 58% were men. Participants were invited for an in-person follow-up evaluation an average of 19.4 months after hospital discharge and had structured face-to-face interviews with two trained physicians.

The primary outcome was overall cognition based on SCIP and MoCA scores. SCIP scores start at 0 and have no upper limit; lower scores indicate greater impairment. MoCA scores range from 0 to 30; scores below 26 are considered abnormal and indicate cognitive impairment. Secondary outcomes included executive function, anxiety, depressive symptoms, and neurological deficits.

At 18-month follow-up, mean SCIP scores were 68.8 for healthy controls, 59.0 for hospitalized COVID patients, and 61.6 for hospitalized controls. Mean MoCA scores were 28.2 for healthy controls, 26.5 for hospitalized COVID patients, and 27.2 for hospitalized controls.

Secondary outcome scores were worse for hospitalized COVID patients than healthy controls, but generally were similar between hospitalized COVID patients and hospitalized controls. However, on the Trail Making Test Part B to assess executive function, COVID patients had worse scores than hospitalized controls, showing a relative mean difference of 15% (P=0.04).

"Previous studies of cognitive function among patients with COVID-19 showed persistent cognitive impairment among 12% to 50% of individuals 1 year after infection," Benros and co-authors noted. "We found that 38% of patients with COVID-19 had MoCA scores below 26 at 18-month follow-up and performed worse in all cognitive tests compared with the healthy population, consistent with previous research."

The study period covered different strains of SARS-CoV-2 with varying virulence and potential for long-term effects, the researchers acknowledged. Other limitations included the use of the SCIP, which has a relatively small cognitive test battery. In addition, pre-pandemic cognitive scores were unavailable.

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