Sleep physiology and critical illness: A narrative review

In health, humans spend approximately one-third of their lives asleep. Sleep involves all organ systems, and it is an inherent mechanism for regulation and optimisation of bodily functions. Critical illness commonly results in a wide range of adverse health outcomes, many of which may theoretically be ameliorated by functions that are enhanced by sleep. Sleep deprivation and its subsequent organ dysfunction leads to muscle weakness, immunocompromise and the cardiovascular changes of the stress responses; these features are common features of critical illness and its sequalae. Sleep is reframed as an inherent mechanism for recovery and repair and a key mechanism for improving critical care outcomes. An understanding of how sleep affects our patients could lead to novel therapies that would enhance their recovery. This review covers sleep physiology, measurements to assess it in the critically ill, common pathological features that impact sleep during critical illness and the logical interventions and areas for research that might optimise sleep related outcomes.