Steven A. Shea, Frank A. J. L. Scheer, Michelle L. Gumz, Sophia A. Eikenberry, Jingyi Qian, Saurabh S. Thosar, Michael J. Sole, Tami A. Martino
Circadian rhythms, governed by the body's endogenous clock mechanism, regulate daily fluctuations in cardiovascular function, optimizing physiological processes like blood pressure regulation, cardiac metabolism, and myocardial repair. Rhythms also align cardiovascular reactivity with predictable environmental and behavioral cycles, enabling normal function and affecting disease susceptibility. Major adverse cardiovascular events, including myocardial infarction, ventricular arrhythmias, and stroke, exhibit a distinct morning peak, with evidence for circadian regulation in cardiovascular health. Indeed, controlled human laboratory studies demonstrate that beyond the influences of sleep and other behaviors, endogenous circadian rhythms independently regulate blood pressure, autonomic nervous system activity, blood clotting, vascular tone, and metabolic function. Additionally, the kidney plays a critical role in circadian sodium handling, fluid balance, and blood pressure control, with disruptions in renal circadian rhythms contributing to hypertension and progression to heart failure. Chronic circadian misalignment resulting from shift work, irregular sleep-wake cycles, or misaligned lifestyle habits is strongly associated with increased cardiovascular risk and disease progression. The emerging field of Circadian Medicine applies circadian principles to clinical care, leveraging interventions such as optimizing light exposure, meal timing, and physical activity to restore biological alignment. Chronotherapy, the strategic timing of medications or procedures to align with a patient's diurnal or circadian rhythms, offers further potential for enhancing treatments and reducing adverse effects. By integrating circadian biology into cardiovascular medicine, novel strategies are emerging to help prevent disease, improve patient outcomes, and enhance therapeutic precision. Understanding the interplay between circadian regulation and cardiovascular physiology provides a foundation for advancing cardiovascular prevention and treatment strategies.