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Relatively young people -- ranging from 38 to 59 years old -- showed cognitive dysfunction or "brain fog" months after being diagnosed with COVID-19, a cross-sectional study found.

More than 7 months after acute infection, a substantial proportion of COVID-19 patients exhibited deficits in processing speed, executive functioning, category fluency, memory encoding, and recall, reported Jacqueline Becker, PhD, of Icahn School of Medicine at Mount Sinai in New York City, and co-authors in a research letter.

Cognitive impairment occurred more frequently in people who were hospitalized for COVID-19 than in those who received outpatient care.

"Our findings have significant public health importance," Becker told MedPage Today. "They have implications for functional and social outcomes, as the relatively young age range of our cohort suggests occupational productivity may be impacted."

COVID-19 survivors , but its prevalence and association with disease severity has not been well characterized, Becker and colleagues noted.

The researchers evaluated 740 COVID-19 patients who had been followed through a Mount Sinai Health System registry from April 2020 to May 2021. All had tested positive for SARS-CoV-2 or had serum antibody positivity, and all had no history of dementia. Mean time from COVID-19 diagnosis was 7.6 months.

Mean age of the group was 49, and 63% were women. About half (54%) were white, 20% were Hispanic, 15% were Black, and 11% were multiracial or other.

Cognitive functioning in specific domains was assessed by Number Span forward (attention) and backward (working memory) measures, Trail Making Test Part A and Part B (processing speed and executive functioning), phonemic and category fluency (language) tests, and the Hopkins Verbal Learning Test-Revised (memory encoding, recall, and recognition).

The researchers calculated the frequency of impairment on each measure as a z score of less than or equal to 1.5 standard deviations below age-, education-, and sex-adjusted norms. Results were adjusted for race and ethnicity, smoking, BMI, comorbidities, and depression.

Of the 740 COVID-19 patients, 51% were treated as outpatients, 27% were hospitalized, and 22% were treated in an emergency department setting.

Overall, the most prominent deficits were in:

• Memory encoding: 24%
• Memory recall: 23%
• Category fluency: 20%
• Processing speed: 18%
• Executive functioning: 16%
• Phonemic fluency: 15%

Hospitalized COVID-19 patients were more likely to have impairments in attention (OR 2.8, 95% CI 1.3-5.9), executive functioning (OR 1.8, 95% CI 1.0-3.4), category fluency (OR 3.0, 95% CI 1.7-5.2), memory encoding (OR 2.3, 95% CI 1.3-4.1), and memory recall (OR 2.2, 95% CI 1.3-3.8) than people in the outpatient group, in adjusted analyses.

COVID-19 patients treated in the emergency department were more likely to have impaired category fluency (OR 1.8, 95% CI 1.1-3.1) and memory encoding (OR 1.7, 95% CI 1.0-3.0) than those treated as outpatients.

"The relative sparing of memory recognition in the context of impaired encoding and recall suggests an executive pattern," Becker and co-authors wrote. "This pattern is consistent with early reports describing a dysexecutive syndrome after COVID-19 and has considerable implications for occupational, psychological, and functional outcomes."

Limitations of the study may have included sampling bias, the researchers noted. Future studies should investigate long-term cognitive trajectories after COVID-19 infection and potential links with neuroimaging findings, they added.

In clinical practice, identifying COVID-19 patients with cognitive impairment early will be crucial "due to the possible reversibility and potential opportunities for interventions, such as cognitive rehabilitation," Becker said. "To that end, cognitive screening of post-COVID-19 patients as standard of care may be prudent, regardless of age and COVID-19 severity."

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