Image Credit: Sonia Miri Hedberg / AI Generated
Scientific Frontline: Extended "At a Glance" Summary: Brain Blood Flow and Post-COVID-19 Fatigue
The Core Concept: People suffering from post-COVID-19 condition (PCC), or long COVID, demonstrate lower cerebral blood flow and slower reaction times, which may contribute to the cognitive fatigue frequently experienced by these individuals.
Key Distinction/Mechanism: Compared to healthy controls, individuals with PCC showed reduced blood flow in brain regions responsible for attention, sensory processing, and cognitive control. This reduced perfusion correlates with slower and more varied reaction times during sustained attention tasks, a pattern indicative of mental fatigue.
Major Frameworks/Components:
- Post-COVID-19 Condition (PCC): A syndrome characterized by persistent symptoms, most notably debilitating cognitive and physical fatigue, following an initial COVID-19 infection.
- Cerebral Perfusion: The flow of blood through the brain, which delivers necessary oxygen and nutrients. Decreased perfusion was observed in specific regions associated with attention and sensory processing.
- Sustained Attention Task: A diagnostic tool used to measure a subject's ability to maintain focus and respond to stimuli over time, revealing slower and more inconsistent performance in patients with PCC.
- Functional Magnetic Resonance Imaging (fMRI): The neuroimaging technique utilized to measure brain activity by detecting changes associated with blood flow.
Branch of Science: Neuroscience, Pathology, Clinical Medicine, and Physiology.
Future Application: These findings could lead to more targeted diagnostic imaging protocols for patients suffering from long COVID and may eventually guide the development of therapeutic interventions aimed at improving cerebral blood flow or mitigating the associated cognitive deficits.
Why It Matters: Fatigue is one of the most disabling and common symptoms of long COVID. Understanding the underlying biological mechanisms, such as altered cerebral perfusion, is a critical step toward validating the physiological reality of the condition and developing effective treatments.
People with post-COVID-19 condition reported higher levels of fatigue and showed slower reaction times than healthy individuals. A new study from Karolinska Institutet, published in NeuroImage: Reports, also found lower blood flow in several parts of the brain, which may be linked to the cognitive difficulties experienced by many people after COVID-19.
Fatigue is one of the most common and disabling symptoms of post-COVID-19 condition (PCC), often referred to as long COVID. Although the condition has been studied extensively since the pandemic, the biological mechanisms behind persistent symptoms are still not fully understood.
A Test of Attention and Fatigue
Researchers at Karolinska Institutet investigated the relationship between fatigue, cognitive performance, and brain blood flow in 22 people with PCC and 19 healthy control participants matched for age and sex.
Participants completed a 20-minute sustained attention task while researchers measured blood flow in the brain using functional magnetic resonance imaging (fMRI). During the test, they were asked to respond as quickly as possible to visual signals.
People with PCC reported a greater increase in fatigue during the task than the control group. They also had consistently slower reaction times.
“Our findings show that people with post-COVID-19 condition not only report more fatigue, but also perform more slowly on a task that requires sustained attention,” says Sonia Miri Hedberg, a doctoral student at the Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, and first author of the study.
Differences in Brain Blood Flow
The researchers also identified differences in cerebral perfusion, the flow of blood through the brain. On average, participants with PCC had slightly lower cerebral blood flow than healthy controls. More pronounced differences were seen in several brain regions involved in attention, sensory processing, and cognitive control.
Further analyses showed that slower reaction times were associated with lower brain blood flow. Participants with PCC also displayed greater variation in their reaction times during the test, a pattern that has previously been linked to mental fatigue in other neurological conditions.
“The study suggests that changes in brain blood flow may be part of the explanation for the fatigue and concentration difficulties described by many patients,” says Sonia Miri Hedberg.
The researchers emphasize that the study cannot establish cause and effect. Because the number of participants was relatively small, the findings need to be confirmed in larger studies. The fMRI method used also cannot fully determine whether the observed differences reflect reduced blood flow in brain tissue or changes in blood transport through the brain’s small blood vessels.
According to the researchers, the findings contribute to a better understanding of the biological changes that may underlie long-lasting fatigue after COVID-19.
Additional information: The study was conducted at the Cognitive Post-COVID Outpatient Clinic at Danderyd Hospital in collaboration with researchers at Karolinska Institutet and Karolinska University Hospital.
Funding: The research was funded by Promobilia.
Disclosure: The authors report no conflicts of interest other than one researcher having received research funding from Promobilia.
Published in journal: NeuroImage: Reports
Authors: Sonia Miri Hedberg, Kristian Borg, Jonas Stenberg, Stina Hedström, Tobias Granberg, Alexandra Gyllenberg, Sven Petersson, Hadrien Van Loo, Love Engström Nordin, and Marika C. Möller
Source/Credit: Karolinska Institutet
Edited by: Scientific Frontline
Reference Number: ns091526_01
