This article recasts the way lighting systems in healthcare estates are commonly valued. We look beyond the carbon footprint savings, and outline the demographic and human resource challenges facing Estates managers. By looking at interior lighting in its full dimension, through its essential attributes (brightness, color temperature, and spatial cognition), Estates and Facilities managers may discover new tools that can mitigate occupant distress issues through environmental design solutions that combat staff burnout, and supply emotional support to patients and their families during delays in discharge, or when bed occupation rates are high. By gaining an understanding of the more complex cognitive and biological ramifications of lighting design in clinical settings, such personnel will gain an integrated outlook on occupant wellbeing that may be instrumental in their decision-making.
Beyond a carbon footprint — the spatial attributes of light
The prevalent cost-benefit analysis carried out on NHS estates regarding facility lighting continues to be viewed through the lens of climate change. The costs associated with the carbon footprint that older, less efficient technologies like fluorescent fixtures exhibit can be calculated with confidence. While this calculation is valuable in helping the NHS achieve its ambitious target of reaching Net Zero emissions for those it controls directly by 2040, it is pertinent to remember that savings earned from the switch to LED fixtures are not the sole benefit.1
Even though energy costs — which include those related to electricity, HVAC, and specialised medical equipment in high demand environments like hospitals, represent about 35% of the operating costs, both the lighting design and the quality of the lighting in clinical spaces enhance (or detract from) staff productivity.2 In fact, the illumination in high-stress medical environments has a direct bearing on both performance and patient outcomes.
Estates and Facilities managers now see a confluence of accumulating factors, many outside their control, which have made operations much more difficult. Chief among these is the maintenance backlog. According to The Health Foundation, the NHS maintenance backlog more than doubled in real terms between 2015/16 (£6.4 bn) and 2023/24 (£13.8 bn).3 This mounting delay has placed NHS estates in dire straits, as many facilities fall into a state of disrepair and/or fail to comply with safety regulations.
However, as Estates personnel await the necessary funding, re-evaluating their upgrade schedule is instrumental to identifying areas where new synergies can redress multiple pain points. Understanding the health outcomes of dynamic lighting design, in terms of fixture-based systems in conjunction with image-based installations, offers such a blueprint.
After the 2024 general election, new Members of Parliament received research briefs on key sectors of governance. The report on healthcare noted that record demand, an ageing population, and inflation, are all squeezing health and social services, and both face significant capacity issues. In England, waiting lists for hospital treatment peaked at 7.8 million people in 2023, and delays in discharge are affecting one in eight general and acute hospital beds.4 These pressures are also prevalent in health and social care services in Scotland and Wales, with Northern Ireland facing a particularly difficult outlook.
In the social sector alone, the Association of Directors of Adult Social Services estimated that in England around 250,000 people were waiting for a care assessment in August 2023.4 Furthermore, the NHS faces a productivity challenge. Despite staff increases to meet soaring patient demand, NHS hospital productivity in 2023/24 remained about 10% lower than its pre-pandemic level (2019),4 and while tracking staff performance depends on what variables are measured, it is apparent that staff burnout and high turnover, as well as higher rates of bed occupation (up to 90% in recent years) — often associated with poorer quality of care and outcomes, all contribute to a more volatile and stressful environment of care.4
Demographic shifts
Furthermore, many of the prevalent dislocations in the healthcare system emerge from significant demographic shifts. Added to this are an ageing infrastructure, macroeconomic shocks like the COVID-19 pandemic, and disruptions to energy supply chains, all of which compound the issues. However, understanding the illumination design-related factors that impact productivity and health outcomes in a hospital is one useful way of mitigating the environmental attributes that depress positive patient outcomes.
Hence, by understanding the three essential properties of light — brightness, color temperature, and daylight’s spatial nature — as they relate to biological regulation and attention modulation, it is possible for Estates and Facilities managers to identify ways to gain immediate advantages in critical spaces. For example, the decline in staff productivity can be partially attributed, not in an insignificant way, to a sub-par, crowded, or isolated working environment. The workplace impacts both the neurochemistry of attention and emotional resilience that are key to effective, empathetic care.
How can lighting enhance staff productivity?
While the physical retrofitting of many clinical spaces takes time and substantial funding, understanding the malleable nature of perception provides an innovative approach to a complex problem. It is pertinent to ask: how can the attributes in lighting design enhance staff productivity, soothe frayed emotions during long waiting times, and even improve health outcomes when bed occupation rates have increased? Understanding how the mind and body respond to sensory-rich stimuli in stressful settings when we’re healing (or working under duress) proves advantageous when considering new lighting systems. This is the purview of an emerging field called Neuroaesthetics.
In 2019, during the European Healthcare Design Conference at the Royal College of Physicians in London, I gave a lecture titled ‘Cognitive Biophilia and Neuroaesthetics: The Restorative Impact of Perceived Open Space’. The presentation introduced a pioneering fMRI study carried out by an architect, an environmental psychologist, a neuroscientist, and an artist with experience creating visual-spatial illusions of nature. The study was published in the peer-reviewed Health Environments Research & Design Journal, the premier publication for evidence-based design (EBD).
This pioneering study, ‘Nature Correlates of Nature Stimuli: an fMRI Study’, was spearheaded by Debajyoti Pati PhD, one of the most published healthcare researchers in the world, and his colleagues Dr. Cherif Amor, PhD, and Dr. Michael O’Boyle, PhD, at Texas Tech University’s College of Human Sciences, its Department of Design, and TTU’s Neuroimaging Institute. The paper examined whether there were unique patterns of brain activation associated with exposure to photographic sky compositions (representing nature stimuli), as compared with other positive, negative, and neutral images.5
The positive impact of nature images on health outcomes has been traditionally measured using behavioural and physiological indicators. The pre-conscious emotional response of positive, negative, and low valence imagery (those that evoke a weak or neutral emotional reaction) was already well understood in terms of their cortical mapping. However, there was a lack of understanding of the underlying neural mechanism that explained the positive emotional influence.
Looking at brain activity
The research team was interested in studying whether nature imagery would enlist other areas of the brain when the staging was perceived as part of the interior envelope of a room, for example, as a credible opening in the ceiling versus a symbolic image that stood out as a 2D surface. While illusions have a rich tradition in Western Art and architecture, their application had not been explored to generate bone fide perceived open space, which can yield therapeutic benefits for occupants in isolated, controlled, or stressful environments.
The study generated brain maps of the neural pathways and regions associated with subjects’ perception of photographic open sky compositions — a photographic process that incorporates 20+ structural and contextual cues that render a credible illusion of vertical volume when properly staged above the ceiling plane. The research team compared the brain scans of subjects exposed with the open sky images to the results of their brain maps when the same subjects were exposed to nature imagery in control categories: positive, negative, and neutral scenes or patterns.
Initial analysis of the brain maps indicated that the photographic open sky compositions, which were captured at a perpendicular (90-degree) angle in relation to the ground, rather than the more common 60-degree angle, shared all the characteristic neural activations of positive images, including the neural correlates that trigger the psycho-physiology’s pleasure response in the Hedonic circuit. At the same time, the sky images that generated the credible illusion of vertical volume activated several other unique cortical regions. Of particular interest to the research team were the activations found in the cerebellum.
Michael O’Boyle, the neuroscientist in the team, noted that higher levels of activity in the cerebellum are often associated with aspects of spatial cognition, in particular the experience of extended space or depth perception.5 This study confirmed parallel research showing that the Parahippocampal Place Area (PPP) and the Retrospenial Complex (RSC) become engaged when we perceive a distant scene as opposed to objects near our bodies. The study was the first one to map the neuroarchitecture of illusory imagery and its effects on perception.
This study earned the best research project of the year, awarded by the International Academy of Design & Health, and the Certificate of Research Excellence (CORE), granted by the Environmental Design Research Association, on account of its rigorous methodology and impact on the design field.6 The study showed that sky illusions could effectively be deployed to alter an occupant’s perceived proximity to a natural exterior. Environmental psychologists have long noted that there’s an inherent asymmetry between temporal and spatial dynamics in human perception. We implicitly use space as a measure of time. In other words, abundant space slows both our metabolism and our perception of time, whereas compressed spaces raise both our cortisol levels and speed up our perceived sense of time (lack of visual exit points generates stress over time).
Illusory overhead sky view
In 2015, a second study by the Texas Tech University team, carried out in collaboration with Covenant Health Hospital, in Lubbock, Texas, set out to study the effect of an illusory overhead sky view in a patient room that (interestingly enough) also featured a real window view. However, the window view in these patient recovery rooms did not overlook a green space or a water feature, but an adjacent building. Studies have found that buildings and materials like glass, steel, and concrete lack the restorative benefits of biophilic materials like stone, wood, or brick. A view to an urban landscape is no substitute for a view to a natural landscape.
The paper, ‘The Impact of Simulated Nature on Patient Outcomes: A Study of Photographic Open Sky Compositions’, was published in the peer-reviewed HERD Journal.7 The study examined the behavioural and clinical impact of overhead sky imagery specifically captured, composed, and installed, above the ceiling plane to generate the convincing illusion of vertical volume (spatial cognition). The eight-month study analysed data from 181 patients who were assigned to identical spaces where the only environmental variable separating the experimental from the control rooms was a 1.2 m x 1.8 m. Luminous SkyCeiling (virtual skylight).
The single-blind study found a difference in acute stress of over half (53.40%), and a difference in anxiety of over a third (34.79%) in patients assigned to the experimental rooms where the illusory skies had been installed.7 At the time, Dr. Pati, the lead investigator, noted that his team was the first to study and quantify a simulated overhead view to nature designed to be perceived not as a representational or decorative scene, but as a bone fide perceived overhead opening above the patient bed.
Today, leading tunable lighting systems aim to support our sleep/wake cycle and performance by providing the appropriate levels of light and spectrum that our physiology requires to maintain alertness, refresh attention, and carry out a host of vital biological functions. As the most powerful external cue for circadian entrainment, the attributes of tunable white artificial daylight are now benchmarked.
Most dynamic lighting systems can affect the human circadian system. The impact of those systems can be quantified in terms of two prevalent metrics. On the one hand, BREEAM, in partnership with The WELL Building Standard, has opted for the Equivalent Melanopic Lux (EML), whereas in the US, the agency responsible for all federal buildings opted to use the Circadian Stimulus (CS), the metric developed at the Lighting Research Center (Rensselaer Polytechnic Institute), which is now the Light and Health Research Center at Mount Sinai.
Differences in metrics
It is worth noting that the EML metric is based on the spectral sensitivity of the intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) that contain a photopigment — melanopsin, a light-sensitive protein. However, it does not account for the absolute sensitivity of the circadian system — from threshold to saturation — as conventionally measured by physiological outcomes like melatonin suppression (the hormone that regulates sleep) or circadian phase shifting. In other words, EML alone cannot be used to predict a biological response. Similarly, illuminance levels (measured in lux) alone cannot predict visual performance. More information is needed in both cases to predict a biological response.
In contrast, the Circadian Stimulus (CS) metric incorporates both the absolute and the spectral sensitivity of the circadian system. The CS model is grounded in the neurophysiology and neuroanatomy of the retina, and represents how light signals received by all photoreceptors — ipRGCs, rods, and cones — are integrated to stimulate the master biological clock (the Suprachiasmatic Nucleus). It is important to emphasise that the CS model is a mathematical construct that approximates the circadian phototransduction mechanisms in the retina; that is, the process by which light is converted into neural signals for the regulation of biological rhythms.
In order to predict nocturnal melatonin suppression or phase shifting in an interior space, additional information about timing, duration, and spatial distribution of the luminous stimuli is needed. With that in mind, CS can be used as a validated light stimulus metric for predicting the effectiveness of a light source in suppressing melatonin and shifting circadian timing. While these outcomes are often studied in night-time contexts, the same CS framework applies to daytime lighting design, where circadian stimulation through melatonin suppression is a desired outcome for supporting alertness and health.
Using manufacturer data and spectrum-based software tools like Dialux or Agi32, EML, based on the CIE S 026/E:2018, is fairly easy to calculate for architects and lighting designers.8 The foundations of the CS metric are more comprehensive, but more complex to calculate. This is why the LHRC offers a CS calculator (https://cscalc.light-health.org/) that facilitates converting photopic illuminance and spectrum to CS, which a knowledgeable lighting designer can work with.
On a related note, a key aspect that has got lost in the mix is that daylight has two other equally restorative effects on our psycho-physiology aside from circadian entrainment. Daylight also modulates focused attention through its intensity variability and its volumetric or spatial nature. In evolutionary terms, our physiology has mapped daylight under the sky’s vast blue canopy. That’s the reason why the ipRGCs are also called the body’s blue-sky detectors. These specialised cells respond to light from above the line of sight.
Furthermore, the areas of the brain responsible for spatial mapping are extremely sensitive to the zenith, the highest point above our heads, and the perceived horizon line, the farthest point in front of us. When we are surrounded by a natural landscape, our Autonomic Nervous System (ANS) triggers a relaxation response, and our body decompresses. In enclosed interiors, we tend to look for visual exit points that provide access to a larger space. Therefore, daylight loses its spatial attribute when it is confined to fixture-based systems that focus on illuminance and spectrum alone.
Work for NASA
In 2022, Foster + Partners invited our studio to participate in a technological capabilities demonstration for a space agency (NASA) that was researching modular habitat deployments for extraterrestrial missions. While the project’s main focus involved 3D printing technology and synthetic proteins as potential building materials, the design team was also interested in the available published research on biophilic illusions of nature, and their ability to create a perceived zenith in an isolated environment.
The Foster + Partners team looked at a new image-based dynamic lighting system called IRIS that uses sky photography in a such a way that overhead installations render a palpable illusion of vertical volume. When the depth illusion seduces our hardwired habits of perception into recognising the sensory-rich stimulus as matching our past experiences of looking up at the sky, the body reaps the benefits of spatial polarity. It turns out that a dramatic change of scale — the ability to look at a much larger spatial footprint, either overhead or on the walls, yields the benefits of Prospect & Refuge, which facilitate cognitive restoration.
The design team was interested in studying this type of illusory installation for its effects on performance and emotional balance on subjects who, in long-term extraterrestrial missions, will spend years in a very small space, far from Earth’s sunrise-to-sunset arc. At the same time, the F+P design team was interested in an image-based lighting function called DiAL (Daylight intensity Algorithm) that modulates light intensity behind a sky illusion in a way that mimics how natural daylight varies in intensity throughout the day.
The IRIS system is unique in that it incorporates correlated colour temperature changes and intensity variability within a virtual skylight system that generates a credible perceived zenith for isolated spaces. The multidisciplinary design team knew that one of the main reasons why working next to a real window view boosts mental acuity and attention restoration is thanks to daylight’s natural variability. Therefore, the ability to mimic these dynamic modulations within a perceived opening would enable astronauts to remap the zenith within their reduced workplace by subconsciously tapping a lifetime’s worth of spatial memories of Earth’s blue canopy. That is the inherent power of illusions; they tap into our physiology’s precognitive ability to measure space outside our conscious awareness.
Mammalian physiology
According to neurobiologists, our mammalian physiology toggles between two Basic Rest Activity Cycles (BRAC). The nocturnal BRAC cycles through non-REM sleep and dreaming periods every 90 to 120 minutes, whereas our diurnal BRAC cycles through periods of focused attention and attention restoration. Our ability to focus is predicated on equally long, cyclical periods where our brain returns to a mode of operating that is called Default Mode Network, a monitoring state that is characterised by low brainwave activity that helps the brain recover from periods of high brainwave activity.
Our brain defaults to attention restoration when we canvas our surroundings at leisure. Environments or lines of sight rich in hierarchies of scale and geometry with fractal sub-symmetries like abundant foliage, rock formations, forests, and natural features like mountains, lakes, and shorelines, all facilitate mental restoration. Gazing at a distance refreshes attention before we can return to a period of high brainwave activity (focused attention, concentration, planning). This is why illusory portals that capture a distant scene, either overhead or in front of the observer — at a realistic scale, activate areas of the brain involved in spatial cognition, and have a profound effect on human wellness.
In conclusion, when combined with image-based tunable lighting systems, dynamic lighting systems can offer much more than circadian phase entrainment. These lighting systems can expand the perceived spatial footprint of clinical interiors that can potentially help mitigate the effects of burnout and emotional distress in crowded hospitals. Estates and facilities managers have a lot on their plates, but studying the specifications, published research, and applied case studies offered by key product developers and manufacturers in the field of lighting design could enable healthcare estates to test and deploy lighting schemes that can help mitigate the detrimental effect of stressed interiors.
David Navarrete
David Navarrete is a Lighthouse Fellow at The Centre for Conscious Design, as well as a member of The Center for Education at the Academy of Neuroscience for Architecture (ANFA) and The Center for Health Design. He is an evidence-based design-accredited (EDAC) science writer and speaker, currently serving as director of Research Initiatives and Education at Sky Factory, a fine arts and digital technology studio that leverages Neuroaesthetics in its design framework. The design and manufacturing company utlilises a fine arts framework, digital technology expertise, and cognitive psychology, to create evidence-based design, biophilic illusions of nature.
David holds a Certificate of Research Excellence (CORE) granted by the Environmental Design Research Association (2017). His essays on Cognitive Biophilia and The Restorative Impact of Perceived Open Space are available online at the NeuroArts Resource Center, an educational initiative spearheaded by the International Arts + Mind Lab, Johns Hopkins University, and the NeuroArts Blueprint.
References
1 NHS England. Delivering a Net Zero NHS. Greener NHS. 4 July, 2022. https://tinyurl.com/52cz4v7j
2 Light Up Energy News. What is the Average Hospital Electric Bill in the UK? Light Up Energy. 29 July, 2024. https://tinyurl.com/35v999d9
3 Fozzard K, Kelly E, Issa Z. The NHS Maintenance Backlog Rising Costs and Falling Investment. The Health Foundation. 20 December 20, 2024. https://tinyurl.com/yv55j74t
4 Powell, T, Baker C, Foster D. Capacity Pressures in Health and Social Care in England. U.K. Parliament, House of Commons Library. 16 July, 2024. https://tinyurl.com/u6e2shnv
5 Pati D, O’Boyle M, Amor C, Hou J, Valipoor S, Fang D. Neural Correlates of Nature Stimuli: An fMRI Study. HERD: Health Environments Research & Design Journal. 2014; 7(2):9-28. https://tinyurl.com/65h4682w
6 Pati D, O’Boyle M, Amor C, Hou J, Valipoor S, Fang D, Navarrete D, and Witherspoon W. Neural Correlates of Nature Stimuli: An fMRI Study. Environmental Design Research Association (EDRA) Certificate of Research Excellence (CORE), Recipient Profiles, 2017. https://www.edra.org/page/2017_Core_Recipients
7 Pati D, Freier P, O’Boyle M, Amor C, Valipoor S. The Impact of Simulated Nature on Patient Outcomes: A Study of Photographic Sky Compositions. HERD: Health Environments Research & Design Journal 2015; 9(2):36-51. https://tinyurl.com/44zfz8tt
8 CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for IPRGC-Influenced Responses to Light. International Commission on Illumination 2018. https://tinyurl.com/yc3k9rvk