CIRCADIAN LIGHTING
conditions. Dementia patients frequently experience disturbed circadian rhythms, waking throughout the night in confusion, which can lead to distress for patients and caregivers alike. A study has demonstrated that adopting adaptive lighting tuned to support the circadian rhythm can significantly improve patient sleep quality; it also contributes to a reduced level of depression and agitation.5
With an ever-
growing elderly population, this research suggests that lighting to support biological rhythms offers tangible practical benefits. More generally, there is the suggestion
that a well-regulated circadian rhythm may enhance drug efficacy, speeding up patient recovery. Human-centric lighting could doubtless benefit long-term patients, helping promote a regular circadian sleep cycle in what would otherwise be an unvarying, statically lit environment. It also has obvious applications for mental health support in maintaining a natural, restive environment.
Potential shortcomings and areas for development As we develop a lighting practice that supports non-visual requirements, we must provide the right light at the right time to cater to all our bodily needs. As we will see, reliance on lighting technology alone has potential shortcomings, and we must think holistically about light provision in buildings. For example, exposure to blue light
from LEDs in the evening and at night can disturb the circadian rhythm by triggering the production of melanopsin at the wrong times. Additionally, researchers from Kings College London have found that artificial blue-spectrum light can induce minimal skin damage and photoageing.6 Furthermore, unlike older lighting
technology, LEDs emit practically no infrared light content. Mitochondria within our cells are powered by blood sugar and the absorption of infrared light in the range of 650 to 900 nanometres. This light recharges the mitochondrial ‘battery’ that powers a cell’s biochemical reactions.
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However, blue light of 420-450 nanometres is also absorbed, with almost the opposite effect, depleting energy. Note that this is close to 480 nm, which causes the greatest melanopic response as seen previously.7
LED light peaks in this blue end of the spectrum, but above 700 nanometres, it tapers off. There is almost no infrared energy to penetrate and recharge the mitochondria. While technological developments may
address this, the best solution is likely to remain sensible sun exposure in the eyes and on the skin. Human-centric lighting systems should incorporate sunlight as much as possible, including harvesting daylight to augment artificial lighting design. It is also important to emphasise the importance of regular meals and quality sleep in maintaining the circadian rhythm – good lighting alone is not a ‘magic bullet’, but rather part of an approach to creating an environment that centres the needs of people rather than, say, functionality or commerce.
Conclusion The uptake of LED lighting technology, replacing outdated and inefficient fluorescent lamps, has been underway for some time. The recent changes to the RoHS Directive that prohibit new T5, T8, and compact fluorescent lamps from being placed on the market in the UK and the EU will only accelerate this changeover.8 The evolution of the human-centric
lighting concept has shown the transformative potential of aligning artificial lighting with our natural circadian rhythms. By harnessing the advanced capabilities of LED technology, particularly its tuneable spectral qualities, we can create lighting environments that support health and well-being. This approach is especially relevant in healthcare settings, where the benefits of dynamic lighting can be profound – enhancing patient recovery, improving sleep quality, and even reducing fall incidents among elderly people. While there is no substitute for sunlight to promote physical and mental health,
holistically integrating natural and controlled artificial light offers a promising path forward. Given the inevitable ubiquity of LED lighting and the potential to incorporate advanced controls and analytics, the opportunity for healthcare practitioners to adopt a human-centred lighting philosophy is a strong one. As research progresses and standards evolve, the implementation of human-centric lighting could become a cornerstone of patient care, paving the way for environments that are not only functional but truly conducive to healing and overall wellbeing.
IFHE
References 1 WHO. IARC Monographs Volume 124: Night Shift Work [
www.iarc.who.int].
2 Boyce P. Editorial: Exploring human-centric lighting. Lighting Research & Technology 2016.
3 Greenberg JM, Gruner KA, Rodney L et al. Biologically aware lighting for newborn intensive care. J Perinatol 2023; 43 (Suppl 1): 49-54
4 Grant LK, St. Hiliare MA, Heller JP, Heller RA, Lockley SW, Rahman SA. Impact of upgraded lighting on falls in care home residents. J Am Med Dir Assoc 2022; 23 (10): 1698-704.
5 Figueiro MG, Sahin L, Kalsher M, Plitnick B, Rea MS. Long-term, all-day exposure to circadian-effective light improves sleep, mood, and behavior in persons with dementia. J Alzheimers Dis Rep 2020; 4 (1): 297-312.
6 Lawrence KP, Sarkany RPE, Acker S, Herzog B, Young AR. A new visible light absorbing organic filter offers superior protection against pigmentation by wavelengths at the UVR-visible boundary region. J Photochem Photobiol B 2022; 227: 112372
7 Kaynezhad P, Fosbury R, Hogg C, Tachtsidis I, Sivaprasad S, Jeffery G. Near-infrared spectroscopy reveals instability in retinal mitochondrial metabolism and haemodynamics with blue light exposure at environmental levels. J Biophotonics 2022; 15 (4): e202100283.
8 DEFRA. RoHS exemption applications: Secretary of State determinations [
www.gov.uk].
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