Delirium

The fundamental concept of delirium is altered consciousness and its fluctuation. Sleep–wake cycle disturbance is one of the common clinical features of delirium. Evidence suggests that disturbed sleep plays a key role in pathogenesis of delirium and restoration of sleep–wake cycle provides a clinical opportunity for prevention of delirium. It is essential to evaluate clinical factors such as medical illnesses, psychiatric disorders, substance use disorders, medication side effects, and environmental factors leading to sleep disturbance in delirium. In addition, multicomponent nonpharmacologic delirium prevention interventions are effective in reducing delirium incidence and preventing falls, with trend toward decreasing length of stay, but nonsignificant reductions in mortality. Approaches to regulating functions of melatonin or orexin on sleep–wake cycle lead to pharmacological interventions, and preventive effects of melatonin receptor agonists and an orexin receptor antagonist on delirium have been shown. This evidence suggests importance of treating sleep–wake cycle disturbance to prevent delirium. More research is warranted to develop comprehensive clinical strategies, targeting sleep disturbance to predict, prevent and treat delirium.