E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedMachine draft
Cardiovascular response to upright tilt in fibromyalgia differs from that in chronic fatigue syndrome.
Naschitz, J E, Rozenbaum, M, Rosner, I et al. · The Journal of rheumatology · 2001
Quick Summary
This study compared how the bodies of people with fibromyalgia and ME/CFS respond to standing up from lying down. Researchers measured blood pressure and heart rate while patients lay down and then tilted upright for 30 minutes. They found that fibromyalgia and ME/CFS patients had very different cardiovascular responses to this position change, suggesting these are two distinct conditions rather than the same illness.
Why It Matters
This study challenges the idea that fibromyalgia and ME/CFS share the same underlying physiological abnormality, which has important implications for understanding ME/CFS pathophysiology and developing targeted treatments. Understanding how ME/CFS differs from other chronic conditions helps establish its distinct biological basis and prevents misdiagnosis or inappropriate treatment approaches.
Observed Findings
- Fibromyalgia patients had a mean discriminant score of -3.68 (SD 2.7), similar to healthy controls at -4.62 (SD 2.24).
- ME/CFS patients had a significantly different mean discriminant score of 3.72 (SD 5.02), differing from both FM and controls (p<0.0001).
- Blood pressure and heart rate response patterns during 30-minute head-up tilt differed substantially between FM and CFS groups.
- Fibromyalgia subgroups with and without fatigue showed comparable cardiovascular response patterns.
Inferred Conclusions
- FM and CFS have dissimilar homeostatic responses to postural challenge, indicating different underlying cardiovascular physiology.
- The similar response between FM patients and healthy controls contrasts sharply with CFS patients, suggesting FM and CFS do not share a common stress-response system derangement.
- Cardiovascular autonomic function may serve as a biological marker to distinguish between these two conditions.
Remaining Questions
- What specific mechanisms drive the divergent cardiovascular responses observed in CFS versus FM?
- Do these cardiovascular differences persist over time or change with disease progression and treatment?
- How do these cardiovascular findings relate to other measures of autonomic dysfunction in ME/CFS (e.g., orthostatic intolerance symptoms, post-exertional malaise)?
What This Study Does Not Prove
This study does not prove that fibromyalgia and ME/CFS are completely separate diseases—only that their cardiovascular responses during tilt differ. It does not establish the cause of these differences, whether they are primary disease mechanisms or secondary effects, or whether other physiological systems show similar or different patterns of divergence.
Tags
Symptom:Orthostatic IntoleranceFatigue
Biomarker:Blood Biomarker
Method Flag:Small SampleMixed Cohort
Metadata
- PMID
- 11409131
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 8 April 2026
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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