Sleep Apnea, Autonomic Disturbances, and Blood Pressure Variability

Abstract

Augmented blood pressure variability has emerged as a quantity predictive of adverse cardiovascular outcomes. Among the range of intrinsic and extrinsic factors shown to increase night-time, circadian, short-term, and long-term blood pressure variations, the presence and severity of obstructive sleep apnea have emerged as one of the most prevalent and potent. Obstructive sleep apnea alters acutely the normal nocturnal equilibrium between sympathetic and parasympathetic tone, magnifying nocturnal blood pressure oscillations, and induces sustained autonomic aftereffects with the capacity to amplify short-term and intersessional blood pressure variabilities. The object of this brief review is to synthesize the current understanding of the potential interrelations between obstructive sleep apnea, the acute and sustained autonomic disturbances that it elicits, and beat-to-beat blood pressure fluctuation during sleep, nocturnal dipping status, and day-to-day blood pressure variability and the consequences of these perturbations for cardiovascular risk.

Keywords: atrial fibrillation; autonomic nervous system; circadian rhythm; sleep apnea, obstructive; sympathetic nervous system.

Figure.

Autonomic disturbances elicited by obstructive sleep apnea (OSA) capable of altering night-time, day-time and inter-session blood pressure (BP) variability. Left, A broad range of intrinsic and extrinsic factors can modify the severity of OSA, calibrated as the apnea-hypopnea index, or indices of oxygen desaturation. Middle, Obstructive apnea during sleep triggers surges in sympathetic nerve firing and attenuates tonic and reflex vagal heart rate (HR) modulation, elicits autonomic aftereffects that carry over into wakefulness, and induces functional and changes in brainstem and cortical regions involved in the generation and modulation of neural outflow and in conduit artery compliance. Right, Through these mechanisms, variation in the severity of OSA from one night to the next could influence an individual’s beat-to-beat BP fluctuation during sleep, nocturnal dipping status, day-to-day BP variability, and consequent cardiovascular risk.