Brain Fog Can Persist 8 Months After COVID: Study

Marcia Frellick

October 22, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

High rates of cognitive dysfunction or brain fog have been found an average of 7.6 months after patients have been treated for COVID-19, new data indicate.

The study of 740 people (mean age 49 years) with no prior history of memory problems included people treated in the outpatient setting as well as those who were admitted to a hospital or treated in emergency departments (EDs).

Jacqueline H. Becker, PhD, Division of General Internal Medicine, Icahn School of Medicine at Mount Sinai, New York City, is first author of the study, which was published online Friday as a research letter in JAMA Network Open.

She and the other authors write that, although older populations are well known to be susceptible to cognitive impairment after a serious illness, this study has implications for younger people as well.


Dr Jacqueline H. Becker

Becker, a clinical neuropsychologist, told Medscape Medical News, "Many people believe that they will survive COVID and they'll be just fine and for the majority of the population I think that's true. But I think our paper suggests there are long-term cognitive repercussions from COVID that may impact individuals across various age groups and the spectrum of disease severity."

Most Common Impairments

The most commonly reported deficits were in processing speed (18%, n = 133), executive functioning (16%, n = 118), phonemic fluency (15%, n = 111), category fluency (tested by listing as many animals as you can in a minute, for instance; 20%, n = 148), memory encoding (24%, n = 178), and memory recall (23%, n = 170).

However, deficits varied by the treatment setting.

Hospitalized patients were more likely to have impairments in attention (odds ratio [OR], 2.8; 95% confidence interval [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 those in the outpatient group.

Patients treated in the ED 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 outpatients. No significant differences in impairments in other domains were observed between groups.

Researchers analyzed data in this cross-sectional study from April 2020 through May 2021. The patients had been diagnosed with COVID-19 and were followed through a Mount Sinai Health System registry.

Authors adjusted for race and ethnicity, smoking status, body mass index, comorbidities, and depression.

Helen Lavretsky, MD, professor in-residence, Department of Psychiatry, University of California, Los Angeles, and a geriatric integrative psychiatrist, told Medscape Medical News that the numbers in this study confirm trends she is seeing in her post-COVID clinic.

"It is devastating for young people, especially, who were in their best health up until they got COVID. Some improve right after COVID, but then lapse and brain fog or cognitive impairment is one of the top three most common symptoms. Others include fatigue and anxiety."

Dr Helen Lavretsky

She said the study echoes the question of other studies in how long these symptoms will last. "Is it forever? We're coming up on almost two years of the same symptoms."

"What Is Astounding Is the Scale"

"Normally people of this age don't have this type of impairment. Maybe in the single-digit proportion," Lavretsky said. "This is not unlike other viral diseases like HIV, for instance or Lyme Disease. What is astounding is the scale — so many have it."

She noted that because so many people have been infected with COVID-19 the numbers with these cognitive effects translate to hundreds of thousands, which will come with great cost to the healthcare system and work productivity losses.

"Disability will break the bank," Lavretsky said. "Within the next year, we will all realize how tremendous this problem is."

Tracy Vannorsdall, PhD, associate professor of psychiatry and behavioral sciences, Johns Hopkins Medicine, Baltimore, Maryland, told Medscape Medical News she is also seeing similar effects after COVID illness.

This study shows that the lasting effects are prevalent at all levels of illness from COVID-19, Vannorsdall said, adding that the findings also add concern to what happens to young COVID survivors as they age.

Dr Tracy Vannorsdall

"Some of the proposed mechanisms for COVID-related cognitive difficulties overlap with those we see in neuro degenerative conditions," she said. "There is an eye toward examining folks and following them long-term to get a sense of whether earlier-life COVID will put people at higher risk for cognitive difficulties later on."

Vannorsdall said the findings of this study suggest clinicians should be asking more questions about cognitive function and memory.

One of the strengths of this study, she said, is that Becker's team used a more detailed cognitive battery than previous literature has shown. The kinds of impairment are differentiated so clinicians can more easily target treatment and rehabilitation to areas of weakness.

Participants were at least 18 years old, spoke English or Spanish, tested positive for SARS-CoV-2 or were positive for antibodies, and had no history of dementia. Age, race, and ethnicity were self-reported.

Researchers used well-validated neuropsychological tools to measure cognitive function: Digit Span Forward (attention) and Backward (working memory), Trail Making Test Part A (processing speed) and Part B (executive functioning), phonemic and category fluency (language), and the Hopkins Verbal Learning Test-Revised (memory encoding, recall, and recognition).

"Previous studies on the topic have been limited by small sample sizes and suboptimal measurement of cognitive functioning," the authors write.

The researchers note that a limitation of the study is that some participants may have presented to Mount Sinai Health System because of health concerns, which could introduce sampling bias.

Becker said they will continue to follow these participants through the registry long-term, and further work will compare them with controls.

Findings may help determine opportunities for intervention and treating reversible symptoms, such as depression, which may contribute to cognitive impairment, Becker said.

"Cognitive screening of post-COVID patients as standard of care may be prudent regardless of COVID severity," she said. "At the system level, I think there's also a great need to implement culturally competent cognitive services to better serve racially and ethnically diverse patients."

A coauthor reports personal fees from Sanofi, Atea Pharmaceuticals, and Banook Group, and grants from Sanofi, Regeneron Pharmaceuticals, and Arnold Consulting outside the submitted work. No other relevant financial relationships were disclosed.

Lavretsky and Vannorsdall report no relevant financial relationships.

JAMA Network Open. Published online October 22, 2021. Full text

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