Light, sleep and circadian rhythm in critical illness

Purpose of reviewSleep and circadian disruption (SCD) are associated with worse outcomes in the ICU population. We discuss sleep, circadian physiology, the role of light in circadian entrainment and its possible role in treating SCD, with special attention to the use of light therapies and ICU design.Recent findingsThe American Thoracic Society recently published an official research statement highlighting key areas required to define and treat ICU SCD. Recent literature has been predominantly observational, describing how both critical illness and the ICU environment might impair normal sleep and impact circadian rhythm. Emerging consensus guidance outlines the need for standardized light metrics in clinical trials investigating effects of light therapies. A recent proof-of-concept randomized controlled trial (RCT) showed improvement in delirium incidence and circadian alignment from ICU room redesign that included a dynamic lighting system (DLS).SummaryFurther investigation is needed to define the optimal physical properties of light therapy in the ICU environment as well as timing and duration of light treatments. Work in this area will inform future circadian-promoting design, as well as multicomponent nonpharmacological protocols, to mitigate ICU SCD with the objective of improving patient outcomes.