Mild obstructive sleep apnea does not modulate baroreflex sensitivity in adult patients

Background: Obstructive sleep apnea (OSA) is a chronic and progressive disease. OSA is associated with increased cardiovascular morbidity and mortality, the risk being more frequently encountered with severe degrees of OSA. Increased sympathetic activation and impaired cardiac autonomic control as reflected by depressed baroreceptor reflex sensitivity (BRS) are possible mechanisms involved in the cardiovascular complications of OSA. However, it is not known at what stage of OSA that changes in BRS appear. The aim of this study was to evaluate BRS in patients with mild OSA. Methods: The study population consisted of 81 overweight patients with mild OSA and 46 body weight-matched non-OSA subjects. BRS, apnea-hypopnea index, body mass index, and metabolic parameters were assessed. The phenylephrine test was used to measure BRS. Results: Patients in the OSA group were slightly but significantly older than the non-OSA population (50.3 +/- 9.3 years vs 45.7 +/- 11.1 years, P=0.02). Body mass index, percentage body fat, blood pressure, fasting glucose, insulin, and lipid levels did not differ between the OSA patients and non-OSA subjects. Absolute BRS values in patients with mild OSA and non-OSA subjects (9.97 +/- 6.70 ms/mmHg vs 10.51 +/- 7.16 ms/mmHg, P=0.67) and BRS values proportional to age-related and sex-related reference values (91.4%+/- 22.7% vs 92.2%+/- 21.8%, P=0.84) did not differ from each other. BRS,50% of the sex-specific reference value was found in 6% of patients with mild OSA and in 2% of non-OSA subjects (P=0.29). Conclusion: Patients with mild OSA did not show evidence of disturbed BRS in comparison with weight-matched non-OSA controls.