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Hospital patients discharged after severe SARS-CoV-2 infection followed one of three cognitive trajectories, longitudinal data showed.

Of 946 severe COVID patients age 50 and older with no previous dementia or memory complaints, 69.0% had no cognitive impairment 1 month after discharge, 20.3% had short-term impairment that resolved in a few months, and 10.7% had long-term impairment that persisted at 1 year, according to Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo Medical School in Brazil, and co-authors.

Cognitive impairment was associated with higher age, less education, and delirium during hospitalization, the researchers reported in .

"This study highlights the importance of frequent cognitive testing to determine patterns of COVID-19 cognitive impairment, given the high frequency of incident cognitive impairment 1 year after hospitalization," Suemoto and colleagues wrote.

Previous research in Wuhan, China showed that the incidence of cognitive impairment 12 months after discharge was 12.45% for older COVID patients. A pooled analysis of nearly 1.3 million COVID-19 cases -- mostly in the U.S. -- suggested that risks of cognitive deficit remained elevated at 2 years.

Suemoto and colleagues analyzed data from COVID patients admitted to Hospital das Clinicas of the University of Sao Paulo Medical School from March to December 2020. The team defined severe COVID as the presence of dyspnea, a respiratory rate of 30 or more breaths per minute, a blood oxygen saturation of 93% or less, a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen of less than 300 mm Hg, or infiltrates in more than 50% of the lung field.

Follow-up assessments were conducted by phone with participants or caregivers at 1, 3, 6, 9, and 12 months after hospital discharge. Cognitive function was evaluated with the 10-point cognitive screener () if the patient could answer, or the 8-item informant interview to differentiate aging and dementia () if the assessment was conducted with a caregiver.

A total of 1,105 adults with severe COVID were evaluated for cognitive function in the year after discharge. Mean age was 64.9, 44% were women, and 63% were white. Overall, 14.4% of participants had a previous dementia diagnosis or substantial memory complaints at baseline.

Baseline predictors of cognitive decline after COVID-19 were:

• Delirium (β -0.483)

• Female sex (β -0.230)

• Frailty before hospitalization (β -0.191)

• Higher platelet count the first day of hospitalization (β -0.101)

• Older age (β -0.013)

• Previous dementia diagnosis or substantial memory complaints (β -0.606)

Analyses excluding participants with a previous dementia diagnosis or memory complaints showed similar results.

Patients with no previous dementia diagnosis or memory complaints who had long-term cognitive impairment at 12 months were mostly young older adults, with a mean age of 65. In-hospital delirium (OR 1.73, P=0.026) was the leading risk factor for persistent cognitive impairment.

This study is important work toward better understanding the long-term effects following severe SARS-CoV-2 infection, noted Tamara Fong, MD, PhD, of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, who wasn't involved with the research.

"From early on in the pandemic, it was observed that delirium rates among patients with COVID-19 ranged between 25% and 30%, and up to 65% in ICU patients," Fong told 番茄社区app. "Delirium is known to accelerate the rate of cognitive decline and be an independent risk factor for long-term cognitive decline and dementia; furthermore, patients with underlying dementia have a 2- to 5-fold increased risk for developing delirium."

Neurologic symptoms related to COVID may be caused by direct infection of brain tissue, immune response, or adverse events related to the hospitalization, Suemoto and colleagues noted. It's possible different mechanisms may play a role in short-term versus long-term cognitive impairment after acute SARS-CoV infection, the researchers added. A recent autopsy study showed activation of the endothelial cells lining the brain's blood vessels and inflammation after COVID, while other postmortem investigations have found the virus in the brain.

The study had several limitations, the researchers acknowledged. Participants came from early waves of the pandemic, before vaccines were available. Questionnaires used to assess cognition were screening tools and domain-specific performance could not be explored. In addition, neuroimaging was not available.

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