Orthostatic intolerance in the chronic fatigue syndrome.
Schondorf, R, Benoit, J, Wein, T et al. · Journal of the autonomic nervous system · 1999 · DOI
Quick Summary
This study looked at whether ME/CFS patients experience problems with blood pressure and heart rate when standing up quickly, a condition called orthostatic intolerance. Researchers tested 75 ME/CFS patients and 48 healthy controls using a tilt table test and other physical challenges. They found that 40% of ME/CFS patients had orthostatic intolerance compared to fewer healthy controls, suggesting this may be an important symptom in some patients that could be treated.
Why It Matters
This study identifies orthostatic intolerance as a distinct, treatable physiological abnormality present in a significant subgroup of ME/CFS patients, which could explain why some patients experience dizziness and fatigue upon standing. Understanding that OI affects only some ME/CFS patients suggests the disease may involve multiple distinct biological subtypes, potentially requiring different treatment approaches. This work supports developing and testing orthostatic tolerance-targeted interventions for eligible patients.
Observed Findings
Forty percent (30/75) of CFS patients exhibited orthostatic intolerance during head-up tilt testing, compared to approximately 17% (8/48) of healthy controls.
Within CFS patients with OI, presentations included neurally-mediated syncope alone (n=16), isolated excessive tachycardia >35 bpm (n=7), and mixed tachycardia plus syncope (n=6).
CFS patients with OI had significantly younger age and shorter disease duration compared to CFS patients without laboratory OI.
Subacute symptom onset was more common in CFS patients with OI than in those without OI.
Responses to Valsalva maneuver and deep breathing were similar between CFS patients and control subjects.
Inferred Conclusions
A clinically identifiable subgroup of CFS patients exists with physiologically-demonstrable orthostatic intolerance that differs from both healthy controls and CFS patients without OI.
Orthostatic intolerance may represent a distinct pathophysiological subtype within CFS that could warrant targeted therapeutic intervention.
The association between subacute onset and presence of OI suggests different disease mechanisms or trajectories between OI-positive and OI-negative CFS patients.
Remaining Questions
What causes orthostatic intolerance in CFS patients, and does it share mechanisms with post-viral autonomic dysfunction in other conditions?
What This Study Does Not Prove
This study does not prove that orthostatic intolerance causes ME/CFS or that correcting OI will cure the disease—it only shows an association in one direction. The cross-sectional design cannot establish whether OI develops as a consequence of CFS or exists independently. The study also does not prove that all ME/CFS patients would benefit from OI-specific treatments, since 60% of patients showed no laboratory evidence of OI.
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 →
Do CFS patients with OI respond better to OI-specific treatments (salt loading, fluids, beta-blockers, compression) compared to CFS patients without OI?
Why do 60% of CFS patients not show laboratory evidence of OI despite potentially experiencing similar clinical symptoms?
Does the presence of OI at baseline predict clinical outcomes, disease progression, or treatment response in longitudinal follow-up?