Differentiation of the Non-dipping Blood Pressure Phenotype in Obstructive Sleep Apnea: An Observational Study

Background: Absence of nocturnal decrease in Blood Pressure (BP) (“non-dipping”) has been shown to be a strong and independent predictor of cardiovascular events, target organ damage, cardiovascular sequela and cardiovascular mortality. Obstructive Sleep Apnea (OSA) has been associated with non-dipping with an estimated prevalence of approximately 50%, but factors associated with non-dipping in OSA patients remain poorly understood. In this study, we examined clinically relevant variables associated with non-dipping in OSA. Methods: Patients (n = 35) undergoing overnight valuation for OSA, laboratory-based polysomnography, structured clinical interviews, and comprehensive metabolic and anthropometric evaluations, and ambulatory BP monitoring for 24 hours. Patients were classified into a) dipping BP group or b) non-dipping BP group, based on (a) a nocturnal systolic BP decrease of 10% - 20% or (b) a systolic BP decrease of < 10%. Results: Patients had moderate and severe OSA (AHI = 34.8 ± 29.1), and 42.9% demonstrated a non-dipping BP pattern. The severity of OSA measures did not differ between dipping group and non-dipping group. However, Wake after Sleep Onset (WASO) and chronicity of insomnia predicts non-dipping BP independent of demographics, sleep stages, anthropometrics, metabolic measures, or arterial stiffness. Conclusion: These findings contribute to a better understanding of the cardiovascular impacts of OSA and indicate that sleep quality should be incorporated into clinical assessments and management of OSA patients.