Sisto, S A, Tapp, W, Drastal, S et al. · Clinical autonomic research : official journal of the Clinical Autonomic Research Society · 1995 · DOI
This study looked at how the vagus nerve—which helps control heart rate and relaxation—works differently in people with ME/CFS compared to healthy people. Researchers had women with ME/CFS and healthy women breathe at different controlled rates while measuring their heart rate patterns. They found that people with ME/CFS had weaker vagal nerve activity overall, suggesting their nervous system may not be able to relax and recover as effectively as healthy people's.
This research provides objective evidence that ME/CFS involves measurable dysfunction of the parasympathetic nervous system, which may explain why patients struggle with symptom recovery and activity intolerance. Understanding these autonomic differences could help explain the pathophysiology behind ME/CFS symptoms and potentially guide future treatment strategies targeting vagal function.
This study does not prove that reduced vagal tone causes ME/CFS symptoms or that improving vagal function would resolve the illness. It only demonstrates an association and cannot establish whether the vagal dysfunction is primary to the disease, secondary to deconditioning, or a consequence of other underlying pathology. The small sample size and cross-sectional design prevent broader conclusions about all ME/CFS patients.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Sisto, S A, Tapp, W, Drastal, S, Bergen, M, DeMasi, I, Cordero, D, et al. (1995). Vagal tone is reduced during paced breathing in patients with the chronic fatigue syndrome.. Clinical autonomic research : official journal of the Clinical Autonomic Research Society. https://doi.org/10.1007/BF01826195
BibTeX
@article{mecfsatlas-sisto-1995-vagal-tone,
author = {Sisto, S A and Tapp, W and Drastal, S and Bergen, M and DeMasi, I and Cordero, D and Natelson, B},
title = {Vagal tone is reduced during paced breathing in patients with the chronic fatigue syndrome.},
journal = {Clinical autonomic research : official journal of the Clinical Autonomic Research Society},
year = {1995},
doi = {10.1007/BF01826195},
note = {PubMed: 7549414},
url = {https://www.mecfsatlas.com/evidence/sisto-1995-vagal-tone},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/sisto-1995-vagal-tone
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