The evening light environment in hospitals can be designed to produce less disruptive effects on the circadian system and improve sleep

Abstract

Study objectives Blue-depleted lighting reduces the disruptive effects of evening artificial light on the circadian system in laboratory experiments, but this has not yet been shown in naturalistic settings. The aim of the current study was to test the effects of residing in an evening blue-depleted light environment (LE) on melatonin levels, sleep, neurocognitive arousal, sleepiness and potential side-effects. Methods The study was undertaken in a new psychiatric hospital unit where dynamic light sources were installed. All light sources in all rooms were blue-depleted in one half of the unit between 1830h and 0700h (melanopic lux range: 7 – 21, melanopic equivalent daylight illuminance range (M-EDI): 6-19, photopic lux range: 55-124), whereas the other had standard lighting (melanopic lux range: 30-70, M-EDI range: 27-63, photopic lux range: 64-136), but was otherwise identical. Twelve healthy adults resided for five days in each light LE in a randomized cross-over trial. Results Melatonin levels were less suppressed in the blue-depleted LE (15%) compared with the normal LE (45%) (p=0.011). DLMO was phase advanced more (1:20h) after residing in the blue-depleted LE than after the normal LE (0:46h) (p=0.008). Total sleep time was 8.1 minutes longer (p=0.032), REM sleep 13.9 minutes longer (p<0.001), and neurocognitive arousal was lower (p=0.042) in the blue-depleted LE. There were no significant differences in subjective sleepiness (p=0.16) or side-effects (p=0.09). Conclusion It is possible to create an evening light environment that has an impact on the circadian system and sleep without serious side-effects. This demonstrates the feasibility and potential benefits of designing buildings or hospital units according to chronobiological principles and provide a basis for studies in both non-clinical and clinical populations.

Melanopic Limits of Metamer Spectral Optimisation in Multi-Channel Smart Lighting Systems

“…Previous works already showed that metamer spectra could be used to affect physiological responses [23,66]. For the practical implementation of metamer spectra, it is essential to use stimuli with a high dynamic in their melanopic radiance at a steady chromaticity target.…”

“…Besides the aspect of saving energy, research is focusing on the implementation of dynamic patterns of light exposure [12], which vary the illumination or the correlated colour temperature (CCT) to support the circadian rhythm [13] or task-related performance [12]. The discovery of intrinsically photosensitive ganglion cells (ipRGCs) [14][15][16][17][18] made clear that besides the image-forming properties of colour and brightness perception [19], the composition of a light spectrum [20] can also affect the human alertness and cognitive performance [6,[21][22][23]. In the outer retina, six subtypes of ipRGCs (M1 to M6) can be distinguished, each with unique morphological, functional and physiological properties projecting to different targets in the brain [24][25][26][27][28][29][30][31].…”

“…For instance, metamer spectra can keep image-forming metrics steady while varying the melanopic excitation for non-visual purposes, offering the possibility to optimise stimuli with a minimum and maximum melanopsin signal. The circadian system can be influenced actively with such stimuli, depending on the melanopic radiance contrast between two metamer spectra [23,66,67].…”

“…In such a data-driven non-parametric approach, this could mean that the melanopic radiance is only indirectly modelled via the CCT without employing the value of metamer spectra. From a practical point of view, a user may prefer a high CCT, but physiologically a low melanopic effect may be recommended at a given time, which could be managed by metamer spectra [23].…”

From Dawn to Dusk – Mimicking Natural Daylight Exposure Improves Circadian Rhythm Entrainment in Patients with Severe Brain Injury

“…Here, photopic illuminance is, compared to light exposure in healthy individuals, usually fairly low during the day and relatively high during the night [30]. This may result in disruptive effects on the circadian system and the sleep-wake cycle [31], which is especially critical for patients with DOC whose arousal levels anyway strongly fluctuate. Beyond this, it is well-known that an impairment of sleep can have detrimental effects on the immune system and the recovery from illness (for a review see [32]).…”