Key points

• Long-term COVID-19 syndrome is real, although the definition of it is still unclear.
• Cognitive problems after COVID-19 can persist for six to twelve months.
• Severe COVID may be associated with long-term cognitive impairments.

It has been over two-and-a-half years since COVID-19 was first diagnosed. Research now confirms what patients have been reporting for a long time: that long-term COVID-19 syndrome does exist. However, there is still no agreement on a clear definition of it.

The list of long-term COVID-19 symptoms maintained by the CDC includes a range of concerns, from fatigue and cognitive problems to muscle pain and digestive disorders, which makes it difficult to come up with a precise definition. Despite that challenge, post-COVID-19 patients need help, and the more we know about this syndrome, the better care can be provided.

Neuroimaging Studies Results

A recent study published in March 2022 is important and unique in COVID-19 research: The researchers were able to compare brain imaging of their study participants before and after COVID-19.

The researchers in England conducted brain studies (MRI) of the participants before the COVID-19 pandemic as a part of a different, longitudinal population study. During the pandemic, some participants tested positive for COVID-19, and some did not. The researchers repeated the MRI on both groups. There were 401 subjects with positive tests for COVID-19 (only 4 percent had been hospitalized) and 394 controls with negative COVID-19 test results. However, some of the controls got sick with pneumonia between the two scans.

The results of subjects who tested positive for COVID showed a reduction in global brain size and changes (reduction in grey matter thickness) in the prefrontal cortex region important for the cognitive process of decision-making and the parahippocampal gyrus that plays an important role in memory encoding and retrieval. There was also tissue damage in the olfactory cortex, important for processing and perceiving smell. These changes were not seen in participants who suffered from pneumonia between their scans.

Najt et al. (2021) reviewed 27 neuroimaging studies of patients with acute and mild COVID. The brain alterations in the olfactory structures (the smell network) and the corpus callosum (a bridge between the right and left brain hemispheres) were seen in 48 percent of cases. There were also alterations in the limbic structures and prefrontal structures which are also part of the smell network.

Cognitive Studies Results

The same researchers in England (Douaud et al., 2022) administered several cognitive tests to the participants who tested positive and negative for COVID-19. The results showed less accuracy and slower responses in subjects who'd tested positive than controls the who had not.

A Dutch study (Heesakkers et al. 2022) included 452 patients, 16 and older, discharged from the ICUs of 11 hospitals. The median ICU stay was 18 days. As a part of the one-year follow-up, the patients were administered a Cognitive Failure Questionnaire; 16.2 percent of the patients reported cognitive symptoms (daily life cognitive failure, etc.) and 26.2 percent had mental-health symptoms (anxiety, depression, PTSD).

A Wuhan, China, study included participants who were 60 years and older and discharged from three COVID-19 hospitals (Liu et al., 2022). The researchers recruited 3,233 COVID-19 survivors for a six-month follow-up after their discharge. From the initial group, they included 1,438 subjects and 438 controls for a 12-month follow-up. Cognitive changes were assessed using the Informant Questionnaire on Cognitive Decline in the Elderly and the Telephone Interview of Cognitive Status-40.

The 12-month follow-up of survivors showed long-term cognitive deficits (memory and attention impairments) in 15 percent of subjects. As well, 9.1 percent of survivors suffered from mild cognitive impairments (MCI), and 3.3 percent had dementia. The researchers concluded that COVID-19, especially severe COVID-19, may be associated with long-term cognitive impairments and increased risk for dementia.

In Summary

The research indicates that even mild COVID-19 causes changes in the brain and can lead to cognitive deficits, so obviously, it is best to do whatever it takes not to get sick. However, if you have had COVID-19 and are experiencing some cognitive deficits, it may be beneficial to contact your community neuropsychology office and complete a neuropsychological evaluation. This will show if you have some cognitive deficits (memory, attention/concentration, information processing, etc.), how much (mild, moderate, severe impairments), and how to improve and/or maintain your cognitive functioning.

Stay safe and healthy, everybody.

Barbara Koltuska-Haskin, Ph.D., is a neuropsychologist in private practice in Albuquerque, New Mexico with over 30 years of clinical experience, and the author of How My Brain Works: A Guide to Understanding It Better and Keeping It Healthy. Her book has won 2 International Book Awards and 5 National Book Awards.