E2 ModerateModerate confidencePEM unclearCross-SectionalPeer-reviewedReviewed
[Chronic fatigue syndrome: study of a consecutive series of 824 cases assessed in two specialized units].
Ruiz, E, Alegre, J, García Quintana, A M et al. · Revista clinica espanola · 2011 · DOI
Quick Summary
This study looked at 824 people with ME/CFS (91% women, average age 48) seen at two specialized clinics between 2008 and 2010. The researchers found that most people had severe fatigue that worsened with activity, sleep problems, and memory/concentration difficulties. Many also had anxiety, dry eyes (sicca syndrome), and fibromyalgia. On average, it took over 9 years for people to get a diagnosis after their symptoms started.
Why It Matters
This large, specialized clinical cohort provides detailed characterization of ME/CFS presentation and validates that Canadian consensus criteria identify a homogeneous patient population. The documentation of the 9-year diagnostic delay and high rates of comorbidity highlights the clinical and social burden of ME/CFS, informing clinical recognition and treatment strategies.
Observed Findings
- 91% of the cohort were women, with mean age of symptom onset 35±11 years and mean time to diagnosis 108±88 months
- Post-exertional malaise (prolonged generalized fatigue after exercise) was the most outstanding diagnostic feature
- 62.5% were not employed at the time of evaluation
- Comorbidities were common: anxiety 83%, sicca syndrome 82%, fibromyalgia 55%
- 63% of patients received pharmacological treatment
Inferred Conclusions
- ME/CFS preferentially affects young to middle-aged women and causes significant employment disability
- Post-exertional malaise, sleep disturbance, and neurocognitive impairment are the core distinguishing features of ME/CFS
- The Canadian consensus criteria define a homogeneous clinical entity and should guide clinical assessment
- Assessment of comorbid conditions is essential in ME/CFS evaluation and management
Remaining Questions
- What explains the average 9-year delay between symptom onset and diagnosis—is it physician unfamiliarity, gradual disease presentation, or both?
- Are the high rates of anxiety and sicca syndrome primary comorbidities or secondary consequences of ME/CFS?
What This Study Does Not Prove
This descriptive cross-sectional study cannot establish causation or why these comorbidities occur with ME/CFS. The lack of age-matched or disease controls means we cannot determine which features are specific to ME/CFS versus general chronic illness. The study does not explain whether the long diagnostic delay is due to physician recognition gaps or disease progression patterns.
Tags
Symptom:Post-Exertional MalaiseCognitive DysfunctionUnrefreshing SleepFatigue
Phenotype:Gradual Onset
Method Flag:No ControlsMixed CohortStrong PhenotypingWeak Case Definition
Metadata
- DOI
- 10.1016/j.rce.2011.02.013
- PMID
- 21794854
- Review status
- Editor reviewed
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 12 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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