Decreased daytime light intensity at nonwindow hospital beds: Comparisons with light intensity at window hospital beds and light exposure in nonhospitalized elderly individuals

Abstract

Light is crucial for the synchronization of internal biological rhythms with environmental rhythms. Hospitalization causes a range of unfavorable medical conditions, including delirium, sleep disturbances, depressed mood, and increased fall, especially in elderly people. The hospital room environment contributes significantly to patients' circadian physiology and behavior; however, few studies have evaluated light intensity in hospital settings. In this study, bedside light intensity during the daytime (6:00-21:00) was measured at 1-min intervals using a light meter on 4869 bed-days at the Inabe General Hospital in Mie, Japan (latitude 35°N), for approximately 1 month in each season. Daytime light exposure in home settings was measured in nonhospitalized elderly individuals (n = 1113) for two consecutive days at 1-min intervals using a wrist light meter. Median daytime light intensities at window and nonwindow hospital beds were 327.9 lux [interquartile range (IQR), 261.5-378.4] and 118.4 lux (IQR, 100.6-142.9), respectively, and daytime light intensity measured in nonhospitalized elderly individuals was 337.3 lux (IQR, 165.5-722.7). Compared with data in nonhospitalized elderly individuals, nonwindow beds were exposed to significantly lower daytime light intensity (p < 0.001), whereas window beds were exposed to similar daytime light intensity to that of home settings (p = 1.00). These results were consistent regardless of seasons (spring, summer, fall, and winter) or room directions (north vs. south facing). The lowest median daytime light intensity was observed at nonwindow beds in north-facing rooms during the winter (84.8 lux; IQR, 76.0-95.8). Further studies evaluating the incidence of in-hospital outcomes between patients hospitalized in window and nonwindow beds are needed.

Human circadian rhythm studies: Practical guidelines for inclusion/exclusion criteria and protocol

“…Light exposure is known to suppress blood and saliva levels of melatonin via the retinohypothalamic pathway and suprachiasmatic nucleus ( Sadun et al, 1984 ). Bright (>2500 lux) light was found to suppress melatonin levels completely ( Arendt, 2005 ) but even overhead lighting of much lower brightness (100 lux from fluorescent bulbs) can cause significant suppression ( Bojkowski et al, 1987 ; Harada, 2004 ; Iwamoto et al, 2018 ). Initially, it was believed melatonin levels decrease linearly in proportion to the light exposure from 700 Lux ( Mayeda et al, 1998 ).…”

Effect of False Windows on Light Exposure and Sleep Quality in Hospitalized Patients

“…Several studies have reported the effects of low levels of light exposure in patients in windowless hospital beds. For example, daylight hours have been reported to be reduced in windowless hospital beds [2]. Furthermore, patients staying in windowless rooms in the intensive care unit have been reported to be more prone to delirium than those in rooms with windows [3].…”