Vreijling, Sarah R, Troudart, Yael, Brosschot, Jos F · Psychosomatic medicine · 2021 · DOI
This study looked at heart rate variability (how much your heart rate changes moment-to-moment) in people with chronic fatigue syndrome, irritable bowel syndrome, and fibromyalgia. Researchers combined results from 58 previous studies and found that patients with these conditions had lower heart rate variability than healthy people, suggesting their nervous systems may not be regulating heart rate as flexibly as they should.
This meta-analysis provides robust evidence that autonomic nervous system dysregulation—specifically reduced parasympathetic activity—is a consistent biological feature across ME/CFS and related syndromes. Understanding this shared mechanism may help explain symptom overlap and guide development of treatments targeting autonomic function.
This study does not establish that autonomic dysregulation *causes* these syndromes; it only shows an association. The findings cannot explain why some individuals develop autonomic dysregulation or whether correcting it would resolve symptoms. Individual variation within each syndrome is substantial, and the mechanisms underlying this dysregulation remain unclear.
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
Vreijling, Sarah R, Troudart, Yael, & Brosschot, Jos F (2021). Reduced Heart Rate Variability in Patients With Medically Unexplained Physical Symptoms: A Meta-Analysis of HF-HRV and RMSSD.. Psychosomatic medicine. https://doi.org/10.1097/PSY.0000000000000874
BibTeX
@article{mecfsatlas-vreijling-2021-reduced-heart,
author = {Vreijling, Sarah R and Troudart, Yael and Brosschot, Jos F},
title = {Reduced Heart Rate Variability in Patients With Medically Unexplained Physical Symptoms: A Meta-Analysis of HF-HRV and RMSSD.},
journal = {Psychosomatic medicine},
year = {2021},
doi = {10.1097/PSY.0000000000000874},
note = {PubMed: 33065584},
url = {https://www.mecfsatlas.com/evidence/vreijling-2021-reduced-heart},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/vreijling-2021-reduced-heart
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