Melatonin for Preventing Postoperative Delirium in Elderly Patients; a Multi-centre Randomized Placebo Controlled Pilot Study

Delirium is defined as an acute and fluctuating disturbance in cognition characterized by alterations in the level of attention and awareness, which develops over a relative short period of time and represents a change from the subject's baseline. Its incidence increases with age and occurs in nearly 50% of elderly inpatients. Postoperative delirium (POD) increases the risk of patient morbidity and mortality and thereby increasing the cost for the health care system. Increased risk of mortality persists even three years after hospitalization, and is an independent risk factor for urinary incontinence, falls, and decubitus ulcers.

A large prospective study of 1341 patients having non-cardiac surgery with a postoperative stay of at least 48 hours, reported an overall incidence of 9% in >50 years and 15% in >70 years. Another recent study involving 566 patients of similar surgical cohort reported an incidence of 24%.

With no current effective treatment, there is a greater focus on prevention of delirium. Approximately 15% of all POD could be preventable. Preventive strategies can be pharmacological and non-pharmacological. Non-pharmacological strategies are multifaceted and involve different interventions. Among attempted pharmacological options, none have really shown much promise and many suffer from associated adverse effects.

Melatonin is a pineal gland hormone that regulates the sleep-wake rhythm. Disruption of the sleep-wake cycle is observed in delirium. Abnormal tryptophan metabolism is hypothesized as a cause for delirium and melatonin supplementation is observed to decrease the breakdown of tryptophan and serotonin through positive feedback. In patients who develop POD, low tryptophan and serum melatonin levels were observed. Other advantages of melatonin, being a natural supplement, include improved sleep, sparing of sedatives, minimal potential for abuse, or hangover effects.

Systematic reviews done with the existing literature specific to melatonin by a literature search of MEDLINE, EMBASE and Cochrane databases for combination of terms "melatonin" and "delirium", restricted to clinical trials and up to October 25, 2017 found one relevant systematic review: this systematic review looked at the use of melatonin for delirium prevention and found four randomized control trials (RCT), out of which three showed positive results and one showed a negative result. Presently, despite its potential to reduce POD and improve sleep, the role of melatonin in the elderly surgical population is uncertain. There is a clear need for a large, well-designed study to establish definitive evidence.