Stewart, J M, Gewitz, M H, Weldon, A et al. · Pediatrics · 1999 · DOI
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.
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.
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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