E2 ModerateModerate confidencePEM not requiredCase-ControlPeer-reviewedReviewed
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Orthostatic instability in a population-based study of chronic fatigue syndrome.
Jones, James F, Nicholson, Ainsley, Nisenbaum, Rosane et al. · The American journal of medicine · 2005 · DOI
Quick Summary
This study tested whether people with ME/CFS have problems with their body's ability to regulate blood pressure and heart rate when changing positions (like standing up). Researchers compared 58 people with ME/CFS to 55 healthy people using a tilt table test. Surprisingly, they found that both groups had similar rates of these problems, suggesting that this particular type of autonomic dysfunction may not be a primary cause of ME/CFS.
Why It Matters
Many ME/CFS patients experience dizziness and heart rate changes when standing, raising the question of whether autonomic dysfunction is central to the disease. This study directly addresses that hypothesis using objective testing in a population-based sample, helping clarify whether treating autonomic dysfunction should be a primary therapeutic focus for ME/CFS.
Observed Findings
30% of ME/CFS subjects showed orthostatic instability on head-up tilt testing, compared to 48% of healthy controls
When orthostatic instability was present, ME/CFS subjects predominantly showed postural orthostatic tachycardia (elevated heart rate), while controls more often showed neurally mediated hypotension (low blood pressure)
Orthostatic intolerance (symptomatic response) occurred only in nonfatigued control subjects, not in ME/CFS subjects
Neither fatigue severity nor illness duration predicted the presence or absence of orthostatic instability
Delayed responses to tilt table testing were common in both groups, possibly related to hydration status
Inferred Conclusions
Orthostatic instability is not significantly more common in ME/CFS than in the general population, suggesting it is not a primary pathogenic mechanism
Primary dysautonomia should be reappraised as a major factor in ME/CFS pathogenesis
Symptoms reported by ME/CFS patients may not correlate with objective autonomic test abnormalities
Remaining Questions
Why do many ME/CFS patients report orthostatic symptoms if objective autonomic testing does not differ from healthy controls?
Could other types of autonomic dysfunction not measured by tilt table testing play a role in ME/CFS?
What This Study Does Not Prove
This study does not prove that autonomic dysfunction plays no role in ME/CFS symptoms—it only shows that orthostatic instability measured by tilt table testing is not uniquely associated with ME/CFS. The findings do not rule out other forms of autonomic dysfunction or explain why some ME/CFS patients report orthostatic symptoms despite normal test results. It also does not establish causation or address whether secondary autonomic changes occur in response to other disease mechanisms.
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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