At the time of this publication, more than 182,000,000 cases of COVID-19 have been diagnosed worldwide. Although most cases are mild to moderate in severity, lasting only a few weeks, the long-term effects of the disease are unknown. Findings from a recent study suggest that COVID-19 causes long-term gray matter losses in areas of the brain involved in taste, smell, and memory.

COVID-19 affects multiple organ systems and elicits a wide range of flu-like symptoms, including cough and fatigue. Many infected persons experience loss of taste or smell, with one study finding that 96 percent of people with active COVID-19 had some loss of smell. Approximately one-third of these had altered smell six to eight weeks after initial diagnosis. Some researchers have hypothesized that SARS-CoV-2, the virus that causes COVID-19, crosses the olfactory mucosa and progresses to the olfactory bulb in the brain, thus gaining access to the nervous system.

The current study involved 782 adults who had undergone initial brain imaging as part of the UK Biobank study. Approximately half of the participants developed COVID-19 after their initial scan (15 of whom were hospitalized), while the remainder (matched for age, sex, and ethnicity) did not. All participants underwent a second scan, and the two scans were compared.

The comparison revealed substantive COVID-19-related damage and gray matter losses in the areas of the brain responsible for taste and smell, especially in the left parahippocampal gyrus, the left superior insula, the left lateral orbitofrontal cortex, the left anterior cingulate cortex, the left supramarginal gyrus, and the right temporal pole. Those who were hospitalized showed losses in smell- and memory-related brain regions, especially in the areas around the left cingulate cortex, the right hippocampus, and the amygdala.

Although these findings have not been peer-reviewed, they suggest that COVID-19 affects the brain in ways that are not fully understood and underscore the need for continued monitoring of COVID-19 patients. The proximity of these losses to areas of the brain responsible for memory raise concerns that people who have had COVID-19 might be at greater risk for developing Alzheimer’s disease or other forms of dementia. A newly formed international consortium is investigating this possibility.

• Link to full study (under review).

• Learn more about COVID-19 in this episode featuring Dr. Roger Seheult.