Chronic fatigue syndrome and fibromyalgia in diagnosed sleep disorders: a further test of the 'unitary' hypothesis.
Pejovic, Slobodanka, Natelson, Benjamin H, Basta, Maria et al. · BMC neurology · 2015 · DOI
Quick Summary
This study looked at whether ME/CFS and fibromyalgia are actually the same condition or different disorders. Researchers compared patients with sleep-breathing problems, sleep insomnia, and healthy controls, measuring how often each group had ME/CFS, fibromyalgia, or both. They found that while both conditions occurred in sleep disorder patients, fibromyalgia was much more common in insomnia patients, whereas ME/CFS appeared in both groups equally—suggesting these may be separate conditions with different causes.
Why It Matters
This study challenges the hypothesis that ME/CFS and fibromyalgia are manifestations of the same underlying process, which has important implications for diagnosis and treatment. Understanding whether these conditions have different causes could lead to more targeted, effective interventions for each disorder. The finding that sleep disorders associate differently with ME/CFS versus fibromyalgia also suggests screening for sleep problems should be part of ME/CFS evaluation.
Observed Findings
CFS occurred in 13% of sleep-disordered breathing patients and higher rates in insomnia patients
Fibromyalgia occurred in 48% of insomnia patients but was rare in sleep-disordered breathing patients
Patients with both CFS and/or FM had significantly higher daytime sleepiness scores than those without these diagnoses
Depressed mood was common in CFS patients, suggesting depression may co-occur or contribute
The differential prevalence of FM between SDB and insomnia groups differed markedly despite both involving sleep problems
Inferred Conclusions
FM and CFS likely have different underlying biological causes, as they distribute differently across sleep disorder types
Sleep evaluation should be considered in ME/CFS patients, particularly those with high daytime sleepiness scores
Treatment of comorbid depression in ME/CFS patients may be beneficial
ME/CFS and fibromyalgia should not be considered manifestations of a single unitary disorder
Remaining Questions
What are the specific pathophysiological mechanisms causing ME/CFS versus fibromyalgia to associate differently with sleep disorders?
What This Study Does Not Prove
This study does not prove that ME/CFS and fibromyalgia are definitely separate diseases—only that they may be, based on their different associations with sleep disorders. It cannot establish causation; sleep disorders might not cause ME/CFS or fibromyalgia, but rather share common underlying mechanisms. The cross-sectional design means we cannot determine temporal relationships or long-term outcomes.
Tags
Symptom:Unrefreshing SleepPainFatigue
Method Flag:Weak Case DefinitionSmall SampleMixed Cohort