Endothelial function in patients with obstructive sleep apnea syndrome but without hypertension

Respiration. 2006;73(6):751-6. doi: 10.1159/000094183. Epub 2006 Jun 22.


Background: Obstructive sleep apnea syndrome (OSAS) influences endothelial function and causes hypertension.

Objectives: 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.

MeSH terms

  • Brachial Artery / diagnostic imaging
  • Brachial Artery / physiopathology
  • Circadian Rhythm / physiology
  • Disease Progression
  • Endothelium, Vascular / physiopathology*
  • Endothelium, Vascular / surgery
  • Female
  • Humans
  • Hypertension / etiology
  • Male
  • Middle Aged
  • Polysomnography
  • Risk Factors
  • Sleep Apnea, Obstructive / complications
  • Sleep Apnea, Obstructive / diagnostic imaging
  • Sleep Apnea, Obstructive / physiopathology*
  • Ultrasonography, Doppler
  • Vasodilation / physiology*