Effects Of Continuous Positive Airway Pressure Treatment On Endothelial Function And Insulin Resistance In Patients With Obstructive Sleep Apnea And The Metabolic Syndrome

Background: Obstructive sleep apnea (OSA) and the metabolic syndrome are recognized as a risk factor for cardiovascular disease. Cardiovascular events have been reported to have a peak incidence in the early hours after waking in OSA patients. This study was designed to examine the influence of OSA on endothelial function in the early morning in patients with the metabolic syndrome. Methods: The severity of sleep-disordered breathing was evaluated by polysomnography in patients with the metabolic syndrome. Ten OSA patients (an apnea-hypopnea index [AHI] >30) with the metabolic syndrome was included in this study, and we also included age-and sex-matched ten non-OSA patients (AHI <5) with the metabolic syndrome in this study. All subjects received pioglitazone for 1 month (1Mo), and then OSA patients received pioglitazone and nasal continuous positive airway pressure (CPAP) treatment for next 1 month (2Mo). Flow-mediated dilatation (FMD) and nitroglycerin-induced dilatation (NID) of brachial artery were measured by using ultrasound system. We also assessed insulin resistance by HOMA-IR. Measurements were performed in the early morning (6:00AM) and the late morning (11:00AM) at baseline, 1Mo, and 2Mo. Results: At baseline, there were not differences in FMD, and NID between the early morning and the late morning. After the treatment with pioglitazone (1Mo), FMD in the non-OSA patients was increased in the early and late morning, but FMD in the OSA patients was increased only in the late morning. After the CPAP treatment (2Mo), FMD in the OSA patients was increased in the early and late morning. HOMA-IR was improved at 1Mo in the non-OSA patients, and was improved at 2Mo in the OSA patients. Conclusion: OSA is associated with endothelial dysfunction in the early morning and insulin resistance in patients with the metabolic syndrome, and CPAP treatment is effective on the improvement of endothelial dysfunction in the early morning in OSA patients with the metabolic syndrome.