A neuroimaging study conducted in China on men who recovered from SARS-CoV-2 Omicron virus infection revealed a reduction in gray matter thickness in the left precuneus and right lateral occipital regions of the brain. Furthermore, the ratio of the right hippocampus volume to the intracranial volume diminished following the Omicron infection. These alterations correlated with changes in specific psychological characteristics. These changes were associated with changes in certain psychological characteristics. The study was published in JAMA Network Open.
The SARS-CoV-2 Omicron variant, a mutation of the novel coronavirus causing COVID-19, was first identified in November 2021. It is distinguished by a significant number of mutations, especially in the spike protein which binds to human cells. These mutations have raised concerns regarding its increased transmissibility, potential resistance to vaccines, and alterations in the severity of the disease compared to earlier virus strains.
Research on infections caused by various coronavirus variants, including Omicron, suggests that they often result in persistent symptoms. These symptoms, which can last over 90 days post-recovery, may include dizziness, headaches, disturbances in smell and taste, as well as neuropsychiatric issues like sleep disorders, depression, anxiety, and cognitive function decline. Moreover, during the acute phase of the infection, many individuals experience neurological symptoms leading to potential brain neural tissue damage.
Study author Yanyao Du and his colleagues wanted to investigate the changes to gray matter and volumes of specific neural structures in the brains of male patients after a SARS-CoV-2 Omicron infection. Gray matter is a key component of the central nervous system, found in the brain and spinal cord, distinguished by its darker color compared to white matter due to its high density of neuronal cell bodies, dendrites, and unmyelinated axons. The researchers were also interested in identifying links between these neural changes and various psychological symptoms of these individuals.
The study involved 61 men with pre-existing functional magnetic resonance imaging scan data before contracting the SARS-CoV-2 Omicron virus. These men had undergone neuroimaging as part of a health screening in August-September 2022 and were later infected with the Omicron variant in January 2023. They revisited the clinic for additional magnetic resonance imaging during the infection period and completed psychological assessments, with 17 participating in follow-up assessments in April 2023. The average age of the participants was 43 years.
After the first and second neuroimaging examinations, the participants completed assessments for depression (Beck Depression Inventory), anxiety (Beck Anxiety Inventory), sleep problems (Insomnia Severity Index), and emotional self-efficacy (Regulatory Self-Efficacy Scale). After the second neuroimaging, they underwent five different cognitive tests and reported their clinical symptoms. Three months post-infection, they reported their clinical symptoms again.
Results showed that one aspect of emotional self-efficacy – despondency-distress was lower after the infection, while the severity of anxiety symptoms increased. Despondency-distress refers to a state of extreme sadness and emotional suffering. The most frequent symptoms reported during the infection were fever, slowed reaction speed, cough, and shortness of breath. Participants also reported decreased appetite.
Compared to pre-infection conditions, there was a decrease in gray matter thickness in the left precuneus and right lateral occipital regions of the brain post Omicron infection. Additionally, the ratio of the right hippocampus volume to the total brain volume also decreased. Participants who experienced high temperatures during the infection showed a reduction in grooves in the right inferior parietal region compared to those who did not.
The thickness of gray matter in the left precuneus region of the brain tended to be lower in individuals with more severe anxiety symptoms. The ratio of the right hippocampus to the total volume of the brain was higher in individuals who scored better on one of the cognitive tests (the Word Fluency Test).
“In this cohort study of 61 male patients with Omicron infection, the gray matter thickness in the left precuneus and right lateral occipital region and the ratio of the right hippocampus volume to the total intracranial volume were significantly reduced in the acute phase [of the infection]. Gray matter thickness and subcortical nuclear volume injury were significantly associated with anxiety and cognitive function,” the study authors concluded.
The study makes an important contribution to the scientific understanding of the effects of SARS-CoV-2 Omicron infection on brain health. However, it also has limitations that need to be taken into account. Notably, all the participants were men. Results in women might not be the same. Additionally, there was only one follow-up neuroimaging, conducted during the infection.
The paper, “Gray Matter Thickness and Subcortical Nuclear Volume in Men After SARS-CoV-2 Omicron Infection”, was authored by Yanyao Du, Wei Zhao, Sihong Huang, Chuxin Huang, Chang Li, Yanjing Chen, Yijie Huang, Longtao Yang, Cong Li, Huiting Zhang, Hu Guo, and Jun Liu.