Event-level nocturnal blood pressure dynamics in obstructive sleep apnea assessed by cuffless monitoring

Abstract Study objectives Obstructive sleep apnea (OSA) contributes to abnormal blood pressure (BP) variability (BPV). While OSA has been linked to increased BPV using intermittent or cuff-based measurements, the hemodynamic responses to individual respiratory events remain poorly understood. We aimed to delineate event-level BP dynamics of OSA using a cuffless continuous monitoring device. Methods We prospectively enrolled adults who underwent overnight polysomnography for suspected OSA. Continuous systolic and diastolic BPs were recorded using a validated cuffless photoplethysmography-based ring device. Time-stamped respiratory events (apnea and hypopnea) were annotated and synchronized with cardiovascular signals. We analyzed the BP, heart rate (HR), and oxygen saturation (SpO₂) trajectories relative to each respiratory event, and applied linear mixed-effects models to evaluate factors influencing BP changes. Participant-level BPV indices, including the standard deviation and average real variability, were calculated throughout the night. Results A total of 12 724 respiratory events from 62 patients were analyzed. Events were followed by a consistent pattern: a BP dip during the event, followed by a rebound surge that peaked at 11.4 s post-event. This peak occurred after the HR peak (8.2 s) but before the SpO₂ nadir (14.7 s). In mixed-effects analyses, longer event duration, apnea (vs. hypopnea), and REM sleep were associated with larger BP fluctuations. At the participant-level, the mean upward duration of event-related BP surges correlated with the SpO₂ nadir. Conclusions OSA induces BP fluctuations at the level of individual respiratory events. These findings demonstrate that OSA influences cardiovascular dynamics at event-level, beyond traditional measures of nocturnal BPV. Statement of Significance Obstructive sleep apnea (OSA) has been linked to increased nocturnal blood pressure (BP) variability and heightened cardiovascular risk. However, prior studies have largely relied on intermittent or cuff-based BP monitoring, limiting the temporal resolution needed to capture hemodynamic responses to individual apneic events. Using a cuffless wearable device, this study demonstrates that OSA induces transient BP fluctuations at the level of individual respiratory events, with characteristic dip-and-surge patterns. Longer events and apneas (vs. hypopneas) are associated with greater BP surges, and time-resolved BP metrics show closer associations with hypoxemia than with event frequency alone. Future research and clinical monitoring strategies may benefit from incorporating high-resolution, cuffless BP tracking to better quantify cardiovascular risk in sleep-disordered breathing.