Circadian Rhythm Sleep-Wake Disorders

Abstract

OBJECTIVE This article provides an overview of advances in the understanding of circadian rhythms and the health implications of circadian disruption. LATEST DEVELOPMENTS Circadian medicine is a relatively new concept, with widespread overlap with many other areas of medicine. Circadian clocks rely on feedback loops that control the expression of many genes. Functional circadian oscillators exist at multiple physiologic levels and facilitate a multimodal clock mechanism. The suprachiasmatic nucleus is the central circadian pacemaker. Peripheral tissues can be entrained by other stimuli (such as food intake) and can uncouple from the suprachiasmatic nucleus pacemaker; this discovery may provide new therapeutic options for circadian rhythm disorders. Numerous modern developments have altered our circadian clocks and these changes are associated with poor health outcomes. ESSENTIAL POINTS Circadian clocks are ubiquitous throughout our body and regulate multiple body functions. Several studies have highlighted that circadian disruption can result in significant negative mental and physical health consequences. A deeper understanding of the effects of misalignment between our circadian clocks and the external environment may ultimately have therapeutic implications for our health.

Insomnia

“…In the case of circadian rhythm sleep-wake disorders, symptoms of insomnia should remit if the person sleeps within their biological sleep window. For more information on these disorders, refer to the article “Circadian Rhythm Sleep-Wake Disorders,” by Flavia B. Consens, MD, 7 in this issue of Continuum .…”

“…Ramelteon, 8 mg, acts as an MT 1 and MT 2 receptor agonist with higher affinity than endogenous melatonin. Melatonin may be more effective for the treatment of circadian rhythm sleep-wake disorders than for insomnia 7 ; when used as a hypnotic, melatonin and melatonin receptor agonists have relatively short half-lives that make them more suitable for inducing sleep onset rather than supporting sleep maintenance, for which they have only shown mild benefit 63 . In addition, the clinician should consider whether the primary aim of melatonin treatment is as a hypnotic or a chronobiotic, as different intended uses have distinct dosing regimens and timings of administration 7 …”