Profile: Paul Nulty, from FX’s Lighting Focus
Paul Nulty debunks the circadian lighting conducive spaces myth, and tackles how very little we know about what ‘circadian’ really means, even as we use artificial light to imitate its effects.
Edited by Jill Entwistle
CIRCADIAN LIGHTING is becoming more widely adopted – or so we’re led to believe. There’s no doubt that much has been documented in recent years about the benefits of circadian lighting, but are we any closer to understanding the term? And what does ‘circadian’ mean in practice when we apply this to a hospitality or commercial space? It’s time to settle something that’s been niggling us for a while – we simply don’t know enough about the subject to accurately affect circadian rhythms with artificial light. And circadian lighting – whatever that is – doesn’t automatically lead to a health and wellness box ticked.
Our understanding of the broader term ‘circadian’ has been reinforced by the huge amount of research that’s gone into this subject. It’s impossible to encapsulate it all in a succinct way, so a general overview will have to do.
If we single out the hospitality sector, where circadian lighting is sometimes touted as a silver bullet for issues around jet lag, it’s difficult to ascertain that we can beat tiredness by having the right light in a hotel guestroom
It’s well documented that circadian rhythms govern how our bodies run and that the 24-hour internal clock is linked to physical and psychological responses such as sleep, body temperature, alertness and hunger. When our circadian rhythm gets out of sync, we need external cues to reset it and light is instrumental in this process.
A third type of photoreceptor in the eye called the ipRGC (intinsically photosenstive retinal ganglion cells, to give them their more cumbersome name) is key to this. These cells are intrinsically photosensitive due to the presence of a light-sensitive protein called melanopsin.
They differ from rods and cones in how they process light – they are not linked to the visual system, but rather the pineal gland – and play an essential role in synchronising circadian rhythms to the 24-hour biological clock.
They sense the presence of light and send signals to the body to cease the production of melatonin. This reduction results in feelings of wakefulness and alertness. When these same receptors sense a reduction in light at the end of the day, signals are sent to the body to increase the production of melatonin. This triggers the start of the sleep cycle. Thanks to recent research, we are aware that this photoreceptor is sensitive to short-wavelength (blue) light. Its discovery has profoundly changed how we design with light.
When we start to talk about how artificial light can be used to infl uence circadian rhythms, things are a bit more ambiguous. Lighting designers understand the need to prioritise quality illumination and consider the spectrum of light being used. Th e industry talks at length about using cool light in the day to stimulate alertness and warm, low-intensity illumination in the evening to aid rest.
It sounds simple, but the truth is that claims are frequently made about circadian lighting that don’t talk about the circadian system at all. Often, the term is nothing more than a buzzword and what we’re referring to is tuneable white light or dim-to-warm schemes where colour temperature and intensity are controlled through scene setting and dimming.
If what we’re alluding to is a dynamic light scheme that is more human focused in its intention, can we genuinely defi ne this as circadian? Personalisation through lighting controls or the ability to vary lighting scenes can trigger an emotional response, but this doesn’t amount to a definition of circadian. For something truly circadian to be achieved, the approach needs to be scientific, and the implementation research based.
In our attempt to get closer to a truer definition of circadian lighting, we need to be clear that affecting someone’s circadian rhythm is different to supporting it. If we listen closely to what leading authorities such as Professor Russell Foster (professor of circadian neuroscience at Oxford University) are saying, we learn that there is a complex relationship between stimulus duration and intensity for entrainment.
Personalisation through lighting controls and the ability to vary lighting scenes can trigger an emotional response that supports rather than affects a person’s circadian system
The correct level of biological entrainment is upwards of 1,000 lux, which means that the threshold for stimulating or resetting a person’s internal biological clock is higher than we’re led to believe. To put this in context, it’s twice what’s required as standard in an office environment and five to six times what most brand guidelines reference for a hotel scheme.
We also need to be aware that the exposure time needed under certain CCT light levels is significantly longer than we think. Add age and prior exposure to light and darkness as other contributing factors (along with lots of other non-lighting factors), and it’s clear that we still have a lot to learn about how circadian lighting can work on a meaningful level.
What does become clear is that we need to move away from talking about circadian lighting as if it’s a design philosophy where one size fits all. A blanket approach to circadian lighting can never be effective as we need to account for causal factors such as geography, age, health, sleep, diet, work patterns and exercise. Without being fully informed about the individual, we could use light in a way that is detrimental to that person. And if we don’t start to look at circadian systems in a more holistic way, the effect will only ever be emotional stimuli, not the biological response that we’re looking for.
If we single out the hospitality sector, where circadian lighting is sometimes touted as a silver bullet for issues around jet lag, it’s difficult to ascertain that we can beat tiredness by having the right light in a hotel guestroom. It’s certainly possible to make a guest’s experience more comfortable by transitioning illuminance levels through the colour spectrum, but can we make claims about being able to reset or impact a person’s body clock with artificial light?
The answer is that we can, but only if quantity and duration of exposure to light have been considered along with providing the right spectrum of illumination. If a guest is only staying for a couple of nights, the lighting scheme must stimulate the circadian system in a short time frame. And without a deep understanding of that guest, including the time-zone they have arrived from, how long they plan to stay, and when they intend to go to sleep, the lighting response can only go so far.
Perhaps if we envisage a scenario where we have an entire guestroom using full spectrum tuneable white light and the capacity to extract data from the guest to get a full picture of their travel experience, a supporting lighting scene could be triggered in response to this. That said, a guest would still require a much higher level of light than is typically provided in a hospitality environment and to be exposed to that level of light for several hours – only then could we even begin to start defining it as a circadian approach in the truest sense.
All of this illustrates why daylight remains so effective at reducing jet lag. When it comes to anything relating to wellbeing, we should always be talking about natural light first. Daylight is the best possible circadian stimulus and will do everything we need if we’re suffering from the effects of jet lag or tiredness.
To get closer to a true understanding of circadian lighting, we need to be honest about the fact that it goes way beyond warm and cool light. If all we are doing is augmenting daylight in the morning and daytime with tuneable white light, we’re guilty of an element of trickery that plays on a person’s psychological rather than physiological perception of light.
As an industry, we must demystify what we mean by circadian lighting and move away from reductive definitions. If we do this, we’ll be able to start having more honest conversations about lighting considerations for health, wellbeing and productivity. Conversations that take into account a person’s whole 24 hours and their exposure to light alongside other factors that influence an individual’s physiological condition.
Designers also need to take responsibility for educating the industry and putting more scientific-based information out there, along with realistic claims about what can be achieved on a project. It’s time to debunk the myths and start using the term circadian correctly. Right now, ‘circadian-ish’ is perhaps the best we have.
