Current pharmaceutical designJul 7, 2015

Disrupted Body Clocks, Delirium, Sleep Problems, and Sepsis in Critically Ill Patients: Possible Benefits of Stronger Light-Dark Cycles and Melatonin Treatment in the ICU

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 30, 2026

Abstract

Circadian misalignment is associated with poor sleep quality, delirium, and impaired septic states in critically ill patients confined to ICUs.

Circadian misalignment, also known as chronodisruption, is linked to negative health outcomes in critically ill patients.
Delirium, sleep impairment, and sepsis are all associated with disturbances in the circadian system.
The ICU environment typically lacks changes that could improve circadian rhythmicity for patients.
Increased light/dark contrast and melatonin treatment may help mitigate circadian disruption.
Understanding the signals that synchronize the circadian clock could enhance healing environments in ICUs.

Simplified

The confinement of critically ill patients in intensive care units (ICU) imposes environmental constancy throughout both day and night (continuous light, noise, caring activities medications, etc.), which has a negative impact on human health by inducing a new syndrome known as circadian misalignment, circadian disruption or chronodisruption (CD). This syndrome contributes to poor sleep quality and delirium, and may impair septic states frequently observed in critically ill patients. However, and although the bidirectional crosstalk between CD with sleep impairment, delirium and inflammation in animal models has been known for years and has been suspected in ICU patients, few changes have been introduced in the environment and management of ICU patients to improve their circadian rhythmicity. Delirium, the most serious condition because it has a severe effect on prognosis and increases mortality, as well as sleep impairment and sepsis, all three of them linked to disorganization of the circadian system in critically ill patients, will be revised considering the functional organization of the circadian system, the main input and output signals that synchronize the clock, including a brief description of the molecular circadian clock machinery, the non-visual effects of light, and the ICU light environment. Finally, the potential usefulness of increased light/dark contrast and melatonin treatment in this context will be analyzed, including some practical countermeasures to minimize circadian disruption and improve circadian system chronoenhancement, helping to make these units optimal healing environments for patients.

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Disrupted Body Clocks, Delirium, Sleep Problems, and Sepsis in Critically Ill Patients: Possible Benefits of Stronger Light-Dark Cycles and Melatonin Treatment in the ICU

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