E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedReviewed
Standard · 3 min
Orthostatic intolerance in adolescent chronic fatigue syndrome.
Stewart, J M, Gewitz, M H, Weldon, A et al. · Pediatrics · 1999 · DOI
Quick Summary
This study looked at how the bodies of adolescents with ME/CFS respond when they stand up or tilt upright. Researchers found that nearly all ME/CFS patients showed significant problems with this response, including rapid heart rate, blood pressure drops, and symptoms like dizziness and fainting. These problems were much more common in ME/CFS patients than in healthy teenagers or those with simple fainting disorders.
Why It Matters
This study provides objective physiological evidence that orthostatic intolerance is a core feature of adolescent ME/CFS, not a coincidental finding. Understanding the specific pattern of autonomic dysfunction (tachycardia with hypotension and venous pooling) may help explain debilitating symptoms and guide targeted treatment approaches.
Observed Findings
25 of 26 CFS patients experienced severe orthostatic symptoms during head-up tilt testing, compared to control groups
15 of 25 CFS patients showed orthostatic tachycardia combined with hypotension
18 of 25 CFS patients displayed signs of venous pooling (acrocyanosis, cool extremities, edema)
None of the healthy control or simple faint patients exhibited comparable findings of tachycardia with acral symptoms
7 of 25 CFS patients experienced syncope (fainting) during testing
Inferred Conclusions
Orthostatic intolerance is highly prevalent in adolescents with ME/CFS
The pattern of orthostatic response in CFS (tachycardia with hypotension and venous pooling) differs from typical vasovagal fainting and suggests a distinct autonomic mechanism
A partial autonomic nervous system defect may contribute to ME/CFS symptomatology
Remaining Questions
Does orthostatic intolerance cause ME/CFS symptoms or develop as a consequence of the disease?
What specific autonomic nervous system dysfunction underlies this pattern of tachycardia with hypotension?
What This Study Does Not Prove
This study does not prove that orthostatic intolerance causes ME/CFS, only that they are strongly associated. It does not establish whether orthostatic intolerance is primary to ME/CFS pathology or secondary to deconditioning or other disease mechanisms. The cross-sectional design cannot determine if treating orthostatic intolerance improves ME/CFS outcomes.
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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