Abstract 13730: Continuous Positive Airway Pressure Does Not Improve Circulating Progenitor Cell Counts or Endothelial Function in Obstructive Sleep Apnea: A Randomised Sham-Controlled Study

Abstract

Background: Obstructive sleep apnea (OSA), characterised by reoccurring apnea/hypopnea that causes intermittent hypoxemia, is associated with endothelial dysfunction and reduced levels of circulating progenitor cells (CPCs). The hypothesis that preventing hypoxic episodes with continuous positive airway pressure (CPAP) could improve these pathophysiologies was investigated in the first sham-controlled CPAP study of CPCs and arteriolar vasodilator activity in OSA.

Methods: CPAP naïve men without diabetes mellitus with moderate-to-severe OSA (age = 49±12 y, apnea hypopnea index (AHI) = 37.6±16.4 events/h, BMI = 31.5±5.7 kg/m2) were randomised in a 12-week double-blind sham-controlled parallel group study to receive either active or sham CPAP. OSA was assessed by overnight in-laboratory polysomnography. CPCs were measured by flow cytometry (CD34, KDR, CD45) and by co-staining cells cultured 7 days on fibronectin with acetylated low-density lipoprotein and lectin. Endothelial function was assessed as reactive hyperemia by peripheral arterial tonometry. All measurements were collected at 0 and 12 wks.

Results: At baseline (n=46), CPC levels and endothelial function did not correlate with OSA severity, however endothelial function did correlate with cultured CPCs (R=0.39, p=0.015). At 12 wks, CPAP treatment (n=20) compared to sham (n=16) significantly decreased AHI (mean between-group difference 36.0 events/h; 95%CI -49.7 to -22.3, p<0.0001). Despite this improvement in OSA, CPAP had no effect on levels of CPC subpopulations (CD34+/KDR+ (564.5 cells/mL; -977.1 to 2106, p=0.45), CD34+/KDR+/CD45- (37.0 cells/mL; 17.7 to 85.7, p=0.13), CD34+/CD45- (1330 cells/mL; -1095 to 3754, p=0.27), CD34+/CD45low (230.2 cells/mL; -350.7 to 7570, p=0.46) and cultured (-43.1 cells/field; -246.9 to 160.6, p=0.67)) or endothelial function (0.27; -0.11 to 0.64, p=0.16) when compared to sham. These results are independent of CPAP compliance, baseline AHI or BMI.

Conclusions: Contrary to results reported from non-sham-controlled studies, 12 weeks of therapeutic CPAP did not improve CPC levels or endothelial function in men with moderate-to-severe OSA when compared to sham control. Our results raise questions about the cardiovascular benefits of CPAP.