Elimination of the Causes of Poor Sleep Underlying Delirium is a Basic Strategy to Prevent Delirium

Delirium is a very common but annoying clinical state that interferes with the treatment of background disease and delays recovery. Delirium is a troublesome condition that exhausts not only the patient but also his/her family and healthcare professionals. Since aging is a risk factor for delirium, how to control delirium is an extremely important issue in an aging society. Phenotype of delirium is so diverse that it is difficult to elucidate the mechanism of individual symptoms, but it is clinically well known that maintaining sleep quality is important in preventing and improving delirium. Drugs and factors that are known to disrupt the sleep-wake cycle also overlap with the risk factors for delirium, indicating the close connection between delirium and sleep. Although the sleep-wake cycle is tightly regulated by many neurotransmitters and hormones, the role of each substance in this cycle is being elucidated in detail. It is well known that acetylcholine is one of the most important neurotransmitters involved in wakefulness, and anticholinergic drugs reduce rapid eye movement sleep. Anticholinergic drugs are also the major drug causing drug-induced delirium. Several clinical studies have reported that melatonin receptor agonists reduce delirium. Some clinical studies have examined the relationship between delirium and environmental factors that interfere with sleep, such as noise and brightness. The purpose of this review is to organize the cause of poor sleep underlying delirium and propose strategies to prevent delirium, based on rich neurological and pharmacological findings of sleep. We consider that elimination of causes of sleep deprivation underlying delirium is one of the most effective prevention strategies for delirium.