title: Endothelial function in patients with obstructive sleep apnea syndrome but without hypertension.
abstract: BACKGROUND
  Obstructive sleep apnea syndrome (OSAS) influences endothelial function and causes hypertension.
  
  
  OBJECTIVE
  Our aim was to evaluate the role of endothelial dysfunction in the pathogenesis of hypertension in OSAS.
  
  
  METHODS
  Twenty-three patients with OSAS but without hypertension and 15 healthy normotensive subjects were investigated. The presence or absence of OSAS was evaluated with a sleep study. Endothelial function was investigated with brachial artery ultrasound examination.
  
  
  RESULTS
  Baseline characteristics were equivalent between the two groups. Minimal oxygen saturation and apnea-hypopnea indexes in the OSAS and control groups were 62.9 +/- 16.5 versus 94.9 +/- 1.1% (p < 0.0001) and 53.1 +/- 20.3 versus 3.8 +/- 0.9 (p < 0.0001), respectively. There was not statistically significant difference between basal brachial artery diameters measured in the morning and in the evening in all groups. Flow-mediated dilation (FMD) values measured in the morning were lower than those measured in the evening in both OSAS patients and the control group: FMD of OSAS patients was 6.04 +/- 3.18% in the morning and 10.38 +/- 4.23% in the evening hours (p = 0.001), and FMD of control subjects was 10.9 +/- 2.6% in the morning and 13.9 +/- 2.32 in the evening hours (p = 0.002). Differences in FMD values measured both in the morning and evening hours in OSAS patients were lower compared with those in control subjects (p < 0.0001 in the morning hours and p = 0.003 in the evening hours).
  
  
  CONCLUSIONS
  We detected a prominent diurnal deterioration in endothelial function in normotensive OSAS patients compared with healthy subjects. This deterioration may occur due to ongoing hypoxemia during the night and it may be a possible cause of hypertension and atherosclerotic cardiovascular diseases in patients with OSAS.
authors.affiliation: Department of Cardiology, Faculty of Medicine, Istanbul University, Istanbul, Turkey. husofcapa@yahoo.com
authors.forename: Huseyin
authors.initials: H
authors.lastname: Oflaz
authors.forename: Caglar
authors.initials: C
authors.lastname: Cuhadaroglu
authors.forename: Burak
authors.initials: B
authors.lastname: Pamukcu
authors.forename: Mehmet
authors.initials: M
authors.lastname: Meric
authors.forename: Turhan
authors.initials: T
authors.lastname: Ece
authors.forename: Erdem
authors.initials: E
authors.lastname: Kasikcioglu
authors.forename: Nevres
authors.initials: N
authors.lastname: Koylan
mesh_terms: D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology; D018450:Disease Progression; D004730:Endothelium, Vascular / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D018608:Ultrasonography, Doppler; D014664:Vasodilation / Q000502:physiology*