E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedReviewed
Standard · 3 min
Autonomic function in patients with chronic fatigue syndrome.
Soetekouw, P M, Lenders, J W, Bleijenberg, G et al. · Clinical autonomic research : official journal of the Clinical Autonomic Research Society · 1999 · DOI
Quick Summary
Researchers tested whether ME/CFS patients have problems with the part of the nervous system that automatically controls heart rate and blood pressure. They compared 37 ME/CFS patients to 38 healthy people using several tests (like standing up quickly, holding their breath, and doing mental math). The study found only minor differences, suggesting that major autonomic problems may not be the primary issue in ME/CFS, though some specific responses to stress were reduced.
Why It Matters
Orthostatic intolerance and autonomic symptoms are common in ME/CFS, making autonomic dysfunction a plausible contributor to fatigue and exercise intolerance. This systematic assessment helps clarify whether autonomic problems represent a core pathophysiologic feature or a secondary symptom, which could influence treatment approaches and validate patient experiences of autonomic symptoms.
Observed Findings
Heart rate response to mental arithmetic was significantly lower in CFS patients (22.6±9.9 bpm) compared to controls (29.5±16.7 bpm; p<0.05).
Respiratory heart rate variation tended to be lower in CFS patients (28.4±10.5 bpm) versus controls (32.2±9.5 bpm; p=0.11).
Systolic and diastolic blood pressure responses during Valsalva maneuver were significantly larger in CFS patients despite many being unable to sustain the maneuver.
At rest, no significant differences in baseline blood pressure or heart rate were observed between groups.
Hemodynamic responses during handgrip exercise were lower in CFS patients, potentially attributable to reduced muscle exertion effort.
Inferred Conclusions
Gross alterations in cardiovascular autonomic function are absent in unselected CFS patients.
Impaired cardiac sympathetic responsiveness to mental stress may represent a subtle autonomic abnormality in CFS.
Autonomic symptom severity does not correlate with detectable hemodynamic abnormalities on reflex testing.
The reduced sympathetic response to stressors does not fully explain CFS pathophysiology.
Remaining Questions
Why do CFS patients show reduced sympathetic response to mental stress but near-normal responses to other stressors?
What This Study Does Not Prove
This study does not prove that autonomic dysfunction plays no role in ME/CFS—it only suggests that major gross alterations may be absent. The findings cannot establish causation, and negative or subtle findings do not rule out localized or region-specific autonomic abnormalities. Additionally, cross-sectional design cannot determine whether any detected differences are primary causes or consequences of the disease.
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 →
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Do subtle autonomic abnormalities contribute to orthostatic intolerance and exercise intolerance in ME/CFS, and can more sensitive testing methods detect them?
How do autonomic findings relate to other pathophysiologic mechanisms in ME/CFS (e.g., mitochondrial dysfunction, post-exertional malaise)?
Can longitudinal or provocation studies (e.g., post-exertional testing) reveal autonomic dysfunction not detected at rest or during single challenges?