First, do no harm: a focus on lighting for healthcare

New evidence shows the central role of light in setting the body clock — from neonatal to end-of-life, acute, and chronic effects, and in supporting shift work. Light is also critical to other physiological functions, including stress, mood, and appetite. Some clinicians even consider lighting to be a medical intervention, with a recent editorial suggesting that current standards constitute a violation of the hippocratic oath: ‘First, do no harm’.1

Circadian lighting mimics the natural progression of the day-night cycle, adjusting intensity and colour temperature throughout the day to support the body’s internal clock, known as the circadian rhythm. This rhythm regulates sleep, hormone production, and other critical bodily functions. You may be familiar with the basic functions of the eye: the pupil and lense that flex to focus the light on the retina, the fragile membrane that floats at the back of the eye. These noisy signals are filtered and compressed through multiple layers of cells before reaching the top layer, which acts a relay station to fire a stream of data along the optic nerve to the visual cortex, tucked away safely at the back of the head. Your brain extracts information from that dynamic data feed to generate your experience of a familiar world: faces, places, and pets.

Just a small part of the picture

We now know that this classic description is only a small part of the picture: around 5% of that top ‘relay station’ layer is sensitive to light in its own right. Even when there are no signals from the rods and cones, these intrinsically photosensitive cells are responding to light all on their own, thanks to a protein called melanopsin, which has a peak sensitivity of around 480 nanometers, or ‘sky blue’. This non-visual pathway sends signals directly to a cluster of glands at the top of the brain stem to drive a potent cocktail of responses: sleep, mood, emotion, and attention.

As we get older, our eyes become slightly cloudy and yellow. A 10-year-old’s eyes will take in up to 100 times more light than their healthy 80-year-old grandmother’s eyes. At the same time, those critical brain structures that regulate hormones linked to sleep, such as melatonin, are shrinking. This natural shift in brain structure is worse in adults living with dementia, so the strength of that natural sleep-wake signal is weaker.2

Until very recently, the colour of a lightbulb was fixed — cool ‘blue-ish’ or warm ‘yellowish’. You could dim an incandescent or halogen lamp, but a fluorescent was either ‘on’ or ‘off’. We might have used a timer or an occupancy sensor to reduce electricity use, but constant switching tended to make them burn out more quickly, so it was often simpler just to leave them all on.

The LED, or light-emitting diode, may look the same as those old technologies, but generates light in a completely different way: a stream of electrons are forced across a semiconducting chip, generating a cloud of photons that are driven through layers of minerals to tune their wavelength or colour. These chips are so small that you can pack multiple units (different colours, or a ‘cool’ and a ‘warm’ white) onto a single board or strip — you may be familiar with the flexible decorative strips.

You can reduce the brightness and change how much light each chip generates simply by adjusting the amount and distribution of electricity going through each element in the array. Provided that the electronics are correctly specified, you design, engineer, and control a lighting system to deliver many of the ‘active ingredients’ that we now know your non-visual system needs to keep your body clock on track.

LED’s ‘remarkable efficiency’

The remarkable efficiency of LED chips, and the fact that they can be dimmed or switched in a fraction of a second, all while maintaining their lifetime hours, means that these new solutions can be up to 80% more energy-efficient than fluorescents, while delivering the same, or greater, light levels. The next generation of light fitting is designed to meet the EU EcoDesign Regulations, which came into force in July this year.3 The LED chip can be taken out and replaced, leaving the housing in place — much like an old light bulb, keeping disruption to your busy working environment to a minimum, and further reducing the carbon footprint over the lifecycle of the installation. As energy costs rise, and pressure to move to zero-carbon solutions grows, many healthcare providers find they can justify the costs of an upgrade in electricity bills alone.4

Increasingly, these smart lighting systems not only deliver granular control 24/7, but they can also be configured to feed information back to the Facilities manager or building owner.

Daylight harvesting and other sensing technologies can be built into the fitting, transforming the humble lightbulb into the gateway to an integrated building management system. Setpoints can be used to dim the artificial light when there is enough natural light in the space, to manage automatic blinds to reduce glare and improve thermal control. They can track occupancy rates and performance across the day and the week to optimise energy use, and plan routine cleaning and maintenance to suit your team’s schedules, saving money on call-out charges, reactive repair, and ad hoc replacement.

These energy and operational savings are substantial, but the most expensive line item for any business is its people. While these ‘soft’ KPIs are harder to measure, research suggests that lighting design, including access to controls,1 actively supports the diverse needs of staff, especially those working shifts, can improve productivity and engagement, and even reduce recruitment costs. The potential to use the data in real time to spot unusual movement and falls can release care staff from routine night-time checks to focus on proactive daytime activities that support resident wellbeing.

If this all sounds complicated and expensive, be reassured: circadian lighting is not rocket science, and the costs are coming down all the time. There are three broad types. The baseline for all circadian lighting systems is fittings known as ‘tunable white’: these fittings include multiple chips that allow the user to shift from ‘cool, focus’ to ‘warm, relaxed’ to suit their mood or the task in hand. ‘Dynamic’ lighting is programmed to shift automatically, generally from bright and cool light in the morning, through to a warmer light in the late afternoon. The standard protocol can be optimised to suit ‘solar’ time, or activity patterns such as night-shift work. This simple change has been shown to improve mood and productivity in offices and schools, especially in settings with little or no access to daylight through a window.

A subset of these dynamic lighting systems is engineered to deliver the specific levels and pattern of light-dark exposure recommended by scientists to support the day-night cycle. This is known as ‘circadian’ lighting. Alongside these ambient lighting strategies, a growing number of clinics and psychiatric units, especially in Nordic countries, are using a targeted intervention known as ‘Bright Light Therapy’ (BLT) to successfully manage depression and other mood disorders. Research suggests that this simple procedure can be as effective as an antidepressant, although BLT is often used as an adjunct to, rather than a replacement for, pharmacology.5 This is similar to the ‘SAD’ lamp you might have used at home, where the patient is exposed to bright light (10,000 lux, roughly the light levels on a bright day outside in the UK) for 30 minutes every morning.

Is this reflected in building standards?

If you’re specifying lighting for a hospital or residential healthcare setting, the system you choose will need to meet a number of rules and guidelines in addition to the basic building regulations for safety, energy efficiency, and accessibility. There are three main documents that a lighting professional or engineering consultant will work with: the CIBSE Lighting Guide for Healthcare (LG02:2019), the CIBSE Lighting Guide for Communal Residential Buildings (LG09:2022), and the European Standard for Workplace Lighting (EN12464-1:2021). The requirements set out in CIBSE LG02 and LG09 focus on visual performance (light levels, colour temperature, glare, and flicker). But EN12464-1 goes beyond these parameters to account for the role of lighting in setting the body clock and the needs of older adults, who tend to need higher light levels, as we’ve seen.

Of course, just as an apple on its own doesn’t constitute a healthy diet, a circadian lighting system won’t transform the health and happiness of patients or staff overnight, and natural daylight should always be the starting point for every design.

The healthcare teams who are seeing the greatest return on their investment today consider the lighting as part of an integrated approach to an environment that actively supports the day-night cycle through a combination of technology and behaviour. This includes technologies such as interactive games to encourage physical and mental activity, acoustic monitoring, and other sensing systems to maintain safety while minimising night-time disruption, tailored lighting zones with personal control for patients and staff, alongside staff training and simple adjustments such as placing furniture near windows to optimise daytime light exposure, using black-out curtains to protect darkness at night, ensuring residents and staff spend time outside, and adjusting the night-time routine to minimise disruption: ‘wide-awake clubs’ in a separate part of the facility for example.

Faced with a dilemma

This leaves the busy hospital or care home engineering or other specifier with a dilemma: whether to settle for ‘business as usual’ minimum legal standards, or embrace this new understanding of the non-visual effects of light and invest in a higher specification with associated upfront costs and the inevitable time and effort needed to think ‘outside the box’.

A growing number of large-scale academic studies, backed up by the experience of individual healthcare providers, are demonstrating that, as part of a broader strategic decision to invest in a healthy circadian cycle, these lighting solutions, especially those that harness daylight, can deliver outstanding value for money, reducing the cost of medication, length of stay, and staff turnover.

One study in a residential care home in Calgary, Canada, found that circadian lighting reduced daytime napping and improved the quality of sleep at night, while reducing sedative medication.6 Another large-scale project in two residential care homes found a 43% reduction in falls under circadian compared with standard lighting conditions.7

Another project — in a specialist recovery clinic for heart attacks — noted a 21% reduction in medication costs for patients with rooms on the bright side of the hospital, compared with those on the darker side of the same building.8 At the other end of the age scale, pre-term infants admitted to the neonatal intensive care unit gained weight more quickly, and went home sooner, under circadian conditions than with standard continuous exposure.9 If one considers staff satisfaction, dynamic lighting has been shown to stabilise circadian cycles and mood in night-shift workers.10 Simple, low-cost interventions on the wards and at nursing stations at night, such as access to switches and dimmers, and blue-depleted wireless light ‘pods’, instead of turning on the overhead lights, improved caregiver satisfaction while reducing patient anxiety.11,12

Conclusions

Lighting is a basic feature of every healthcare facility, alongside plumbing, heating and cooling, and security. Until very recently, we believed that the only job of a lightbulb was to help us to see clearly and move around safely, while keeping energy costs to a minimum. We now know that the right light at the right time has the potential to transform our ability to sleep and recover from acute and chronic conditions, and to support the health and satisfaction of the dedicated care teams who work through the night. For the first time in history, not only do we have these insights, but we have the technology to deliver the optimal conditions to support the body clock and reduce energy use too. Perhaps it’s time to give the humble lightbulb, hiding in plain sight, the attention it deserves.

* For more information on the IHEEM Innovation in Healthcare 2024 conference at Uttoxeter Racecourse on 11 September, and to book a place, visit https://tinyurl.com/f5k3a8fa

References

1 Cain SW, Phillips AJK. Do no harm: the beginning of the age of healthy hospital lighting. Sleep, 44(3). https://tinyurl.com/87sb7skw

2 Ecodesign for Sustainable Products Regulation. European Commission, 18 July 2024. https://tinyurl.com/ycshzhcw

3 Hadi K, DuBose JR, Ryherd E. (2016). Lighting and Nurses at Medical—Surgical Units: Impact of Lighting Conditions on Nurses’ Performance and Satisfaction. HERD: Health Environments Research & Design Journal 2016; 9(3), 17-30. https://tinyurl.com/3v5bwwby

4 Hosseini SN, Walton JC, Sheikh Ansari I, Kreidler N, Nelson RJ (2024). An Architectural Solution to a Biological Problem: A Systematic Review of Lighting Designs in Healthcare Environments. Applied Sciences 2024: 14(7), 2945. https://tinyurl.com/yck8hcyc

5 Maruani J, Geoffroy PA (2019). Bright Light as a Personalized Precision Treatment of Mood Disorders [Review]. Front Psychiatry. https://tinyurl.com/43385vu4

6 Constantinescu A, Warness JR, Virk N, Perez G, Shankel M, Holroyd-Leduc J. Optimizing Sleep for Residents in Long-Term Care Without Sedatives. Annals of Long-Term Care 1 October 2019. https://tinyurl.com/5n7whfjt

7 Grant LK, St Hilaire MA, Heller JP, Heller RA, Lockley SW, Rahman SA. (2022). Impact of Upgraded Lighting on Falls in Care Home Residents. J Am Med Dir Assoc 2022; 23(10), 1698-1704.e1692. https://tinyurl.com/54ec992p

8 Walch JM, Rabin BS, Day R, Williams JN, Choi K, Kang JD. (2005). The effect of sunlight on postoperative analgesic medication use: a prospective study of patients undergoing spinal surgery. Psychosom Med 2005; 67(1), 156-163. https://tinyurl.com/58nx2pku

9 Sánchez-Sánchez M, García TL, Heredia D, Reséndiz I, Cruz L, Santiago J et al. (2022). Effect of a light-darkness cycle on the body weight gain of preterm infants admitted to the neonatal intensive care unit. Sci Rep 2022; 12(1), 17569. https://tinyurl.com/52ut9y4x

10 Lowden A, Kecklund G. (2021). Considerations on how to light the night-shift. Lighting Research & Technology 2021; 53(5), 437-452. https://tinyurl.com/2sj4avbh

11 Albala L, Bober T, Hale G, Warfield B, Collins ML, Merritt Z et al. (2019). Effect on nurse and patient experience: overnight use of blue-depleted illumination. BMJ Open Qual 2019; 8(3). https://tinyurl.com/mwz3fw2y

12 Hadi K, DuBose JR, Ryherd E. (2016). Lighting and Nurses at Medical—Surgical Units: Impact of Lighting Conditions on Nurses’ Performance and Satisfaction. HERD 2016: 9(3), 17-30. https://tinyurl.com/4m4n6xa2