Long COVID patients with persistent neurological symptoms are more likely to suffer immune system dysregulation, according to a small study.
The patients were also found having problems with their autonomic nervous system, which controls unconscious functions of the body such as breathing, heart rate, and blood pressure.
Reported neurologic symptoms among long COVID range from headaches and loss of taste and smell to sleep disturbances and cognitive impairment with difficulties in concentration, language and executive function, and clinically significant depression and anxiety.
The study by researchers at the US National Institutes of Health (NIH) offers insight into biological mechanisms, and may help researchers better characterise the condition and explore possible therapeutic strategies, such as immunotherapy.
"Taken together, the findings add to growing evidence that widespread immunological and autonomic nervous system changes may contribute to long COVID," said Avindra Nath, clinical director, National Institute of Neurological Disorders and Stroke (NINDS), part of NIH.
Twelve people with persistent neurological symptoms after SARS-CoV-2 infection were intensely studied at the NIH and were found to have differences in their immune cell profiles and autonomic dysfunction.
Researchers used an approach called deep phenotyping to closely examine the clinical and biological features of long COVID in 12 people who had long-lasting, disabling neurological symptoms after COVID-19. Most participants had mild symptoms during their acute infection.
At the NIH Clinical Centre, participants underwent comprehensive testing, which included a clinical exam, questionnaires, advanced brain imaging, blood and cerebrospinal fluid tests, and autonomic function tests.
The results showed that people with Long COVID had lower levels of CD4+ and CD8+ T cells — immune cells involved in coordinating the immune system's response to viruses — compared to healthy controls. Researchers also found increases in the numbers of B cells and other types of immune cells, suggesting that immune dysregulation may play a role in mediating long COVID.
Consistent with recent studies, people with long COVID also had problems with their autonomic nervous system. Autonomic testing showed abnormalities in control of vascular tone, heart rate, and blood pressure with a change in posture.
More research is needed to determine if these changes are related to fatigue, cognitive difficulties, and other lingering symptoms.
The findings are published in the journal Neurology: Neuroimmunology & Neuroinflammation.
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