Ulas, Umit H, Chelimsky, Thomas C, Chelimsky, Gisela et al. · Clinical autonomic research : official journal of the Clinical Autonomic Research Society · 2010 · DOI
This study looked at hospital records of over 305,000 patients admitted for fainting (syncope) to see which health conditions were more common in women versus men. Researchers found that women were more likely to have several conditions related to nervous system problems that control blood pressure and heart rate, including chronic fatigue syndrome, migraines, and postural tachycardia syndrome (a condition where heart rate increases abnormally when standing). These autonomic conditions were especially common in women of reproductive age.
This study is relevant to ME/CFS because it identifies chronic fatigue syndrome as a significant comorbidity in women presenting with syncope, occurring at 33% higher frequency than in men. The findings highlight important sex-based differences in autonomic dysfunction patterns, which may inform understanding of why ME/CFS patients—predominantly women—frequently experience fainting, dizziness, and blood pressure dysregulation. Understanding these comorbidity patterns may help clinicians recognize and manage multiple interconnected autonomic conditions in ME/CFS populations.
This study does not establish causality—it cannot determine whether syncope causes these comorbidities, whether these conditions cause syncope, or whether they share a common underlying mechanism. The cross-sectional design captures only hospital admissions for syncope, potentially missing cases managed in outpatient settings and introducing selection bias. The study also does not explain *why* women have higher rates of these autonomic conditions or establish whether sex hormones, genetic factors, or other mechanisms are responsible.
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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