Nocturnal blood pressure and nocturnal blood pressure fluctuations: the effect of short-term CPAP therapy and their association with the severity of obstructive sleep apnea.

STUDY OBJECTIVES We determined the relationship of cardiovascular risk factors (CRF), cardiovascular diseases (CVD), nocturnal blood pressure (NBP) and nocturnal blood pressure fluctuations (NBPFs) with the severity of obstructive sleep apnea (OSA). We also investigated the effect of short-term continuous positive airway pressure (CPAP) therapy on NBP parameters. METHODS This retrospective study included 548 patients from our cardiac clinic with suspected OSA. Patients underwent polysomnography and continuous NBP measurement using the pulse transit time (PTT). According to their apnea-hypopnea index (AHI), patients were subclassified: Controls (AHI < 5/h), mild (AHI 5 - < 15/h), moderate (AHI 15 - < 30/h) and severe OSA (AHI ≥ 30/h). 294 patients received CPAP therapy. RESULTS Analysis of covariance (ANCOVA) showed that NBP and the frequency of NBPFs were the highest in severe followed by moderate and mild OSA (all p < 0.001). Multivariable regression analysis revealed a significant association of NBPFs with AHI, BMI, systolic NBP and lowest SpO2. The severity of OSA is also associated with the frequency of obesity, hypertension, diabetes mellitus, atrial fibrillation, heart failure (all p < 0.001) and coronary artery disease (p = 0.035). Short-term CPAP decreased the frequency of NBPFs in all OSA groups and the systolic NBP in severe and moderate but not in mild OSA. CONCLUSIONS The severity of OSA is associated with an increase in NBP and NBPFs. CPAP reduces NBP parameters already after the first night. In addition to BP, the diagnosis and therapy of NBPFs should be considered in patients with OSA. CLINICAL TRIAL REGISTRATION Registry: German Clinical Trials Register; Title: Nocturnal blood pressure and nocturnal blood pressure fluctuations associated with the severity of obstructive sleep apnea; Identifier: DRKS00024087; URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00024087.