SARS-CoV-2 induces somnolence in many in the post-Covid-19 phase

What is somnolence?

Somnolence is a state where a person feels continuously sleepy and drowsy despite having enough sleep. It goes beyond regular tiredness, making it difficult to stay awake and focus on daily tasks.

Covid-19 and post-Covid somnolence

After recovering from Covid, many people report experiencing somnolence. They feel overwhelmingly sleepy, even after a full night’s rest. This condition is troubling because it prevents them from performing their usual activities, affecting their ability to work and complete household chores.

The study

A recent study led by Dr Claudia Chien and her colleagues at Charité -Universitätsmedizin Berlin-Germany looked into why so many post-Covid patients are experiencing this persistent sleepiness. The researchers found that changes in brain perfusion and oxygen levels might be the culprits.

Understanding brain perfusion and oxygen levels

Brain perfusion refers to the blood flow in the brain, which is crucial for delivering oxygen and nutrients to brain tissues. Proper oxygen levels in the brain are essential for normal functioning. When these levels are altered, it can affect various brain functions, including attention and alertness.

Key findings from the study

The study involved 47 post-Covid patients and 47 healthy controls. Using advanced imaging techniques, the researchers observed that post-Covid patients had significantly lower oxygen levels in their brains, particularly in the white matter and cortical grey matter.

Interestingly, while the overall brain perfusion did not differ much between the two groups, specific areas like the caudate nucleus showed delayed perfusion in post-Covid patients. This delay was associated with better executive function, indicating a complex relationship between blood flow, oxygen levels, and brain function.

How does this affect patients?

Patients with post-Covid syndrome reported high levels of fatigue and daytime sleepiness. Nearly 80% of the patients experienced severe fatigue, and about 45% had significant daytime sleepiness. These symptoms were closely linked to the observed changes in brain oxygen levels and perfusion.

Why does this happen?

During the acute phase of Covid, the virus can cause vascular inflammation and dysfunction, leading to long-term changes in blood flow and oxygen delivery to the brain. These changes might persist even after the infection has cleared, leading to symptoms like somnolence.

The impact of lower oxygen levels

Lower oxygen levels in the brain were found to be related to higher risks of daytime sleepiness and cognitive fatigue. For example, decreased oxygen levels in the putamen were associated with a reduced risk of poor cognitive outcomes. In contrast, lower thalamic oxygen levels increased the risk of cognitive fatigue.

Potential adaptations

The researchers suggest that the brain might be undergoing metabolic adaptations to cope with these changes. For instance, increased cerebral metabolism in certain areas might be a compensatory mechanism to maintain normal brain function despite the reduced oxygen levels.

What can be done?

Understanding these changes is crucial for developing targeted treatments for post-Covid symptoms. By identifying the specific brain regions affected and the nature of these changes, healthcare providers can better address the persistent symptoms experienced by post-Covid patients.

The study highlights the importance of continued research into the long-term effects of Covid on the brain. While the pandemic’s acute phase might be over for many, its lingering impact on brain function remains a significant concern. Addressing somnolence and other post-Covid symptoms requires a deeper understanding of how the virus affects brain perfusion and oxygen levels. This knowledge will be key to helping patients regain their normal lives and improve their overall well-being.