Autonomic phenotyping, brain blood flow control, and cognitive-motor-integration in Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome: A pilot study. — CFSMEATLAS
Autonomic phenotyping, brain blood flow control, and cognitive-motor-integration in Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome: A pilot study.
Badhwar, Smriti, Pereira, Tania J, Kerr, Kathleen et al. · Autonomic neuroscience : basic & clinical · 2025 · DOI
Quick Summary
This study compared how the nervous systems of ME/CFS patients, Long COVID patients, and healthy people respond to physical stress tests like breathing different air mixtures and tilting upright. The researchers found that ME/CFS and Long COVID patients had different patterns of problems: ME/CFS patients showed difficulty controlling blood flow to the brain during one test, which was linked to coordination problems, while Long COVID patients had lower oxygen levels when upright and their nervous systems didn't adapt as well.
Why It Matters
This mechanistic study provides the first direct evidence that ME/CFS and Long COVID, despite clinical similarities, may involve distinct physiological dysfunction patterns—one affecting brain blood flow control and coordination, the other affecting oxygen handling during position changes. Understanding these differences could guide more targeted diagnostic approaches and inform why some Long COVID patients progress to ME/CFS.
Observed Findings
ME/CFS patients showed greater reduction of cerebrovascular resistance during hypercapnia (p=0.041) and impaired cerebrovascular autoregulation (p=0.042).
ME/CFS patients demonstrated impaired cognitive-motor integration compared to controls (p<0.02).
Long COVID patients had reduced peripheral and end-tidal oxygen levels (p<0.04).
Long COVID patients showed less vagal withdrawal during head-up tilt (p=0.028).
Both groups showed similar resting vascular function and hemodynamic responses to hypoxia, hypercapnia, and head-up tilt compared to healthy controls.
Inferred Conclusions
ME/CFS and Long COVID represent distinct autonomic phenotypes despite clinical symptom overlap.
ME/CFS involves impaired brain blood flow autoregulation during hypercapnia, potentially contributing to cognitive-motor integration deficits.
Long COVID involves oxygen desaturation during upright posture with blunted parasympathetic response, suggesting a different physiological dysfunction pattern.
These phenotypic differences may reflect disease severity, duration, or unique aspects of COVID-19 pathology rather than a shared mechanism.
Remaining Questions
Do these mechanistic differences persist or evolve in severe ME/CFS patients, or are they specific to mild/moderate disease?
What This Study Does Not Prove
This pilot study does not prove these mechanisms cause the symptom burden in ME/CFS or Long COVID, only that they are associated. The small sample size (12 ME/CFS, 9 Long COVID) limits statistical power and generalizability, particularly to severe ME/CFS patients who were excluded. The study cannot establish whether observed differences reflect disease severity, duration, distinct pathophysiology, or unique aspects of COVID-19 infection.
Do Long COVID patients who progress to ME/CFS develop the cerebrovascular autoregulation impairment observed in primary ME/CFS?
Can these autonomic phenotypes predict treatment response or clinical outcomes, and should they inform personalized therapeutic strategies?
Are the observed brain blood flow changes in ME/CFS causally linked to cognitive-motor dysfunction, or are they independent manifestations of the same underlying pathology?