title: Sex influences endothelial function in sleep-disordered breathing.
abstract: BACKGROUND
  The bases for the association between sleep-disordered breathing (SDB) and cardiovascular disease are poorly understood. Endothelial dysfunction, assessed with brachial artery ultrasonography, may predict cardiovascular risk and represent preclinical vascular disease. We determined whether flow-mediated dilation (FMD) and peak blood flow (PBF) increase after cuff occlusion is altered with SDB.
  
  
  METHODS
  193 participants (58% women) in a cohort study were studied with overnight polysomnography and subsequent brachial artery ultrasonography. SDB was quantified using the apnea-hypopnea index (AHI) and indexes of overnight desaturation and arousal frequency. Two-dimensional and Doppler-velocity measurements of the brachial artery were obtained at baseline and after 5 minutes of upper-arm cuff occlusion. FMD and PBF were defined as the percentage changes from baseline in brachial artery diameter and flow, respectively.
  
  
  RESULTS
  In the entire sample, the AHI was inversely associated with both FMD (r = -0.30, P < .001) and PBF (r = -0.20, P < .001). However, sex-stratified univariate analyses showed that these relationships were exclusive to women. Specifically, FMD was significantly lower in women with an AHI > or = 15 than in women with lower AHI scores (P < .005), with no relationship between AHI and FMD in men. Additionally, PBF decreased significantly with increasing AHI (r = -0.29, P = .010) in women alone. Statistical modeling, adjusting for body mass index, age, and other covariates, similarly showed that SDB severity significantly influenced FMD and PBF, with significant interactions between sex and AHI, reinforcing that the associations between SDB severity and endothelial function were stronger in women than in men.
  
  
  CONCLUSIONS
  Moderate levels of SBD are associated with impaired conduit and resistance endothelial function in women. Women with SDB may be more vulnerable to early SDB-related cardiovascular disease than are men.
authors.affiliation: Division of Cardiology, Case Western Reserve University, University Hospitals of Cleveland, OH, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Faulx
authors.forename: Emma K
authors.initials: EK
authors.lastname: Larkin
authors.forename: Brian D
authors.initials: BD
authors.lastname: Hoit
authors.forename: Joan E
authors.initials: JE
authors.lastname: Aylor
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Wright
authors.forename: Susan
authors.initials: S
authors.lastname: Redline
mesh_terms: D000328:Adult; D000886:Anthropometry; D015992:Body Mass Index; D015331:Cohort Studies; D004562:Electrocardiography; D004569:Electroencephalography; D004576:Electromyography; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography; D012720:Severity of Illness Index; D017678:Sex Distribution; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology