Tick–tock–tick–tock: the impact of circadian rhythm disorders on cardiovascular health and wellness

Humans spend a third of their lives asleep. A well–balanced synchrony between sleep and wakefulness is needed to maintain a healthy lifestyle. Optimal sleep is based on an individual's inherent sleep requirement and circadian rhythm. If either one or both of these critical elements are disrupted, daytime dysfunction, non–restorative sleep, and/or reduced sense of well-being may result. While the medical community is more familiar with sleep disorders such as sleep apnea, insomnia, and narcolepsy, circadian rhythm sleep wake disorders (CRSWDs) are less known, despite these being common within the general population. CRSWDs are comprised of the following: shiftwork disorder, delayed sleep phase disorder, advanced sleep phase disorder, jet lag disorder, non–24–hour sleep–wake disorder, and irregular sleep–wake rhythm disorder. In general, a CRSWD results when there is misalignment between the sleep pattern and the desired sleep schedule, dictated by work, family, and social schedules. Subsequently, patients have difficulty falling asleep, maintaining sleep, and/or experience poor quality sleep predisposing them to insomnia or excessive sleepiness. In this article, we review the core concepts related to sleep, and sleep deprivation in the context of CRSWDs.