Effect of continuous positive airway pressure on soluble CD40 ligand in patients with obstructive sleep apnea syndrome

Background: Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for atherosclerosis. CD40-CD40 ligand interaction promotes several proinflammatory mediators and plays a pivotal role in the various stages of atherosclerotic diseases. The present study examines whether CD40 ligation contributes to outcomes in patients with OSAS. Methods: The study population comprised OSAS patients with an apnea hypopnea index (AHI) >= 30 (n = 35) and control subjects (AHI < 5; n = 16). We measured serum levels of soluble CD40 ligand (sCD40L), tumor necrosis factor (TNF)-alpha, and hypersensitive C-reactive protein (hsCRP) before and after nasal continuous positive airway pressure (nCPAP) therapy for 3 months. Results: Baseline levels of sCD40L were significantly higher in patients with OSAS (6.93 +/- 4.64 ng/mL) [mean SD] than in control subjects (3.43 +/- 2.11 ng/mL, p < 0.01). Baseline levels of sCD40L positively correlated with TNF-alpha but not with hsCRP. The elevation of sCD40L was improved for 1 night after nCPAP therapy (3.83 +/- 2.78 ng/mL, p < 0.001). Even though patients with severe OSAS did not receive any other medication to control atherosclerotic risk factors for 3 months, nCPAP was continued to reduce the levels of sCD40L. Conclusion: The present study suggested that sCD40L is a key factor that links OSAS and atherosclerotic progression.