Melatonin receptor 1b and risk of delirium

Abstract

Background.- A disturbed sleePC-wake cycle is one of the key features of delirium. The hormone melatonin regulates the sleePCwake cycle through its effect on the biological clock via the melatonin receptors. Genetic variations in the melatonin receptor could contribute to susceptibility to delirium. Objectives.- The purpose of this study was to investigate whether genetic variants in the MRNR1B gene are associated with delirium. Methods.- Patients aged 65 years and older hospitalized with an acute internal disease or after a hip fracture were included. Delirium was diagnosed using the Confusion Assessment Method; pre-existent cognitive functioning with the IQCODE-SF; physical functioning with the Katz-ADL. In the MRNR1B gen, 5 gene polymorphisms were determined (rs18030962, rs3781638, rs10830963, rs156244 and rs4753426). Results.- Fifty-three percent of 171 surgical patients and 33% of 699 surgical patients developed delirium. Delirious patients were older (82.8 vs 77.6 years) and more often had pre-existing functional (64 vs 36%) or cognitive impairment (83 vs 26%) (P < 0.001). None of the polymorphisms was found to be significantly associated with the occurrence of delirium in different analysis. Conclusions.- Although the MRNR1B gene is a promising candidate gene for delirium in the elderly based on its functions in melatonin regulation, functional genetic variations were not associated with delirium. Still, the disturbed sleePC-wake cycle in delirium plays an important role in the pathophysiology based on non-genetic research.