Continuous positive nasal airway pressure decreases levels of serum amyloid A and improves autonomic function in obstructive sleep apnea syndrome

Background: Obstructive sleep apnea syndrome (OSAS) is associated with the pathogenesis of cardiovascular disease, and inflammation and autonomic dysfunction. We investigated levels of serum amyloid A (SAA), a marker of inflammation, as well as autonomic nervous activity and pulse wave velocity (PWV) before and after nasal continuous positive airway pressure (nCPAP) therapy in patients with obstructive sleep apnea. Methods and results: We separated 116 patients who were diagnosed with OSAS by polysomnography according to the apnea hypopnea index (AHI) into the following groups: Group 1 without or with mild OSAS (AHI<20, n = 35), Group 2 with moderate OSAS (20 = <40, n = 35) and Group 3 with severe OSAS (AHI >= 40, n = 46). Serum level of SAA (p < 0.05), brachial-ankle PWV (p < 0.05) and BP (p < 0.005) were significantly higher in Group 3 than in Group 1. Autonomic nervous activity assessed by autoregressive spectral analysis of heart rate variability showed that high frequency (HF) power, an indicator of vagal activity, was decreased in Groups 2 and 3 (p < 0.05) and that low frequency/HF, an indicator of sympathetic activity, was increased in Group 3 (p < 0.05). After 3 months of nCPAP therapy in Group 3 (n = 38), SAA (p < 0.05), PWV (p < 0.001) and BP (p < 0.05) were significantly decreased. Conclusion: Markers of inflammation and autonomic dysfunction are increased in patients with OSAS, and nCPAP might help to reduce these risk factors for cardiovascular diseases. (C) 2008 Elsevier Ireland Ltd. All rights reserved.