Humancentric lighting

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The biologicaleffects oflighting
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The biologicaleffects of lighting
Employers are increasingly realizing that people are theirgreatest asset, not just their highest cost. To attract and retain
talent, employees’ health and wellbeing is a high priority
because they know flourishing employees are what drive a
thriving business. As 90% of business costs are staff related,investing in comfort can be one of the fastest ways to boost
efficiency. So, it’s not surprising that many organizations are
keen to enhance workplace comfort and use health andwellbeing building certifications as guidance and proof points.

What is human-centric lighting?
Lighting has a profound effect on people. The reason
is simple; light is the most powerful regulator of ourcircadian rhythm. Light has visual, biological, andemotional benefits. This is paramount for humancentric lighting for people’s health and wellbeing.
Investing in human-centric lighting makes perfectbusiness sense because healthy and engaged
employees make a positive contribution toproductivity. In fact, leading employee experience firmDecisionWise found that disengaged employees costorganizations an average of $3,400 a year for every$10,000 in annual salary1. Those who are committed toan organization, emotionally as well as mentally, arelikely to perform best at work and will miss 20% fewer
work days2.

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At Signify, we have a deep understanding of theeffects that light can have on people, coupled withthe technological know-how to deliver quality
solutions that enhance visual comfort, wellbeing andperformance. As human-centric lighting applications
gather momentum, we have the expertise to delivera wide range of high-quality lighting solutions thatbuilding occupants, facility managers and installers
can use to create more inclusive and satisfying
workspaces. Light has a visual impact (see better),an emotional impact (feel better) and a biologicalimpact (function better).

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Light to see better
A good lighting design supports the illumination ofobjects in the central vision, with balanced lighting in
the peripheral vision to provide optimal eye comfort.
Light that supports people to see better creates
exactly the right balance between clarity and comfort,
while taking into account the specific user needs in theenvironment. One challenge that is present in society
today, and implicitly in workplaces is aging. The eyealready starts to deteriorate around age 453, whichmeans that approximately one third of the potential
working population is already facing reduced vision.
Research conducted by Signify confirms this situationand found that visual acuity and perceived comfort
can be improved by increasing light levels4. This isrelevant since visual fatigue and discomfort have beenreported to relate to ergonomic complaints such as
pain in neck and shoulder5,6. Other research indicatesthat users across age groups tend to prefer higher
light levels for more demanding tasks7,8, while lower
levels are often experienced as more relaxing for theeyes9. The right light depends on the task at hand, but
it is clear that a conducive working environment, andcomfortable vision, relies on well-balanced lighting
design for spaces.

Light to feel better
Another crucial element is the emotional benefitof natural light to make people feel better. Positiveeffects of light on behavior, mood, satisfaction,and comfort have been intensively studied in thepast years10,11. The concept of Biophilia, the practiceof incorporating nature and natural elements
into the built environment, is an especially strong
contributor to this. Biophilic Design has been provento measurably reduce stress, enhance cognitive
function and creativity, boost productivity andincrease wellbeing12. Specifically, access to naturallight and views of the outdoors has been identified
as the number one valued attribute of the workplaceenvironment13. In offices with natural elements,
such as plants and sunlight, a 15% higher level ofwellbeing, 6% higher level of productivity, and 15%higher level of creativity have been reported14. Other
research shows that bright light exposure, via artificial
skylights, generates psychological comfort, increased
productivity, and assumed health15,16. Since the naturallight benefits of seeing better, functioning better and4feeling better are interdependent, efforts to influence
one will always relate to influencing the other two.
As a consequence, designing spaces must balancethese three elements, with the aim of satisfying theneeds and desires of the people using the space,
while addressing the regulations and requirements
for the space.

Light to function better
Light also enables people to function better. To be
active during the day and rest well at night, our bodyneeds a stable predictive cycle that is synchronized
to the natural day rhythm. Preferably in the morning,people need a boost in energy and focus, to function
effectively during the day. Morning light plays asignificant role in triggering this energy boost, andbright light during the day enhances circadian rhythm,
regulating the sleep-wake cycle. Traditional workplacedesign focusses on providing light that is good forvision and in line with the norms in indoor spaces:
300-500 lx. However, natural daylight levels are muchhigher than these levels, ranging from 10,000-100,000
lx. Exposure to higher indoor illuminance levels of atleast 1,000 lx, has been proven to increase alertness
and performance17.
Besides light quantity expressed in intensity, thelight quality expressed in spectral distribution plays
an important role for people’s health and wellbeing.
Specifically, light enriched in the 450-530 nm range
is proven to be an effective and powerful light signal
to regulate the timing, robustness and rhythmicityof the body clock18,19,20, thus directly impacting theability to stay alert and focused (for work or learning)
during the day or to fall (or remain) asleep at night.
The spectral sensitivity of humans for light in therange of 450-530 nm has been related to specificintrinsically photosensitive ganglion cells in the retina
and is also referred to as melanopic light. However,
the effectiveness of light to regulate the body clock
does not just depend on the intensity and spectral
composition of light. It is also influenced by exposure
duration, prior light history, and timing of the light
exposure, as well as individual sensitivity to light.

Light nutrition and the sleep-wake cycle
To be active during the day and sleep well at night, ourbody needs a stable predictive cycle that tells it when
to expect darkness or light. It’s the suprachiasmatic
nucleus (SCN) which is responsible for controlling
circadian rhythms. This is a tiny region of the brain in
the hypothalamus.
But for most people, this central pacemaker in thebrain is likely to have a clock that’s longer than
24 hours21. That means if it’s not entrained to theexternal light/dark cycle, it will rapidly start to run
out of sync - even if the periods of light remained
constant. Furthermore, synchronizing the SCN andother clocks in the body takes time. That’s why wedon’t adapt instantly to changes in the light-darkcycle, and explains why we experience jetlag22,23.
This phenomenon was experienced in 1962 when
Michel Siffre, a French geologist, spent two months in
an underground glacier near Nice. With no access tosunlight, clocks or calendars, he let his body dictate
his sleep-wake cycle. His journal later revealed that

although he spent a third of his time sleeping, as hewould normally do, his sleep-wake cycle was not
24 hours, but was, in fact, 24 hours and 30 minutes.
In the absence of light, Siffre had started living
according to his own internal time, rather that his
body clock, which is governed by the rising andsetting of the sun.
But can we see this phenomenon in our everyday
lives? Actually yes. Because today there is a significant
incidence of circadian misalignment in the general
population. A weak and/or irregular circadian rhythm
is a risk to people’s health: it can lead to poor sleep,depression, weight gain and even cancer24. Sleep
deficiency is associated with an increased riskof obesity, diabetes, cardiovascular disease anddepression25.

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The biological clock and circadian rhythms
Almost all cells in the human body need input fromthe outside world to synchronize with the daily light/
dark cycle. The central pacemaker, which is locatedin the SCN, just behind the eyes 26,27, plays a keyrole. The SCN has around 20,000 neurons divided
into a light-sensitive part and a non-light sensitive
part28,22. The non-light sensitive part drives ourinternal circadian rhythms without any external input,
telling the body when to expect darkness or light.
In contrast, the light-sensitive part, which receives
input from the eyes, adjusts our internal clock tochanging external circumstances, such as when thelength of daytime changes with the seasons. Levelsof melatonin and the core body temperature trigger
signals from the SCN to the rest of the body to give it
an estimate of the external light/dark cycle29. Thesesignals drive a whole range of other processes in thebody with 24-hour rhythms, such as heart rate, bloodpressure and the release of hormones like cortisol
and insulin30 - all of which have a strong influence on
the sleep/wake cycle (Figure 1). There are many morebiological processess that are influenced by ipRGC
photoreception. Scientists discovered for instancedirect pathways to the mood and learning centers inthe brain31.
Light enables us to see the world around us.
Traditionally, indoor lighting was mainly driven byvisual requirements. It is only relatively recently thatHighcortisol=activeHighmelatonin=sleepduring the day

at night

Figure 1: The alternating presence of the hormones cortisol and melatonina novel photoreceptor type in the inner retina wasdiscovered, fundamentally challenging this traditionalview32. It is now known that, in addition to stimulating
the visual system, light incident on the retina
stimulates other biological functions - also referred
to as non-visual responses (Figure 2). Light regulates
our day and night rhythm and helps us to function
better. In addition, light creates atmosphere and sets
our mood, it evokes specific emotions and helps us
to feel better.

Cognitive
performance

Non visual

Mood

Sleep
MemorySpectral sensitivity

VisualNon visual system
Visual system

400

500

600700
Wavelengths (nm)Figure 2: Visual and non-visual impact of light on people33

6VisualBiological
Emotional

Hormones

Biological active light

So, what is melanopic DER?

Around the beginning of the 21st century, it was
discovered that some ganglion cells in the retina arelight sensitive with a peak sensitivity around 480 nm(the cyan part of the spectrum). Electric light that
activates these cells is known as biological active
light or circadian light. This is quantified using themelanopic daylight efficacy ratio (melanopic DER).
It is this ratio, coupled with the amount of light that
falls into the eye, that measures how well a lighting
design supports people’s biorhythms. Light in themorning triggers us to wake up and bright lightduring the day enhances our circadian rhythm, which
regulates our sleepwake cycle, daytime engagement
and mood. However, during the night the opposite
is true. Deep, more efficient sleep is importantfor health and wellbeing. In the short term it aids
alertness, learning and memory, improves our safety,
strengthens restoration, enhances our mood and ispart of a healthy lifestyle. In the long term, that helps
to develop an active immune system, healthy brain
and is good for our cardiometabolic health. Therefore
at night, a low activation is required in applications
such as hospital patient rooms or 24/7 environments
like emergency call centers.

Melanopic DER is a spectral metric of the biologicaleffect of artificial light source compared to daylight(6500K). The melanopic DER of a reference daylight
spectrum is 1. Typically, artificial lighting has a lower
biological effect than daylight, the melanopic DER
being below 1.

Brighter office lighting
So, we know that sufficient light nutrition during theday makes us less sensitive to late-evening light topromote sound sleep and an easy wake up. But wealso need light that supports how we see, feel andfunction at work. And that requires brighter officelight - high intensity, cyan-enhanced lighting that
falls comfortably into the eye. Because solutions withbiological active light, comfortable brightness and ahigh activation during the day offer the most effective
way to create a healthy office environment. That
raises a challenge. Because replicating the 10,000 to
100,000 lux that people experience outdoors is notrealistic, or efficient, in an indoor setting. People also
have a preference for lighting that does not have too
cold a color temperature.
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Philips BioUp technology
Philips BioUp technology enhances the LED spectrumwith cyan light. This increases the biological impactof the light. With BioUp the melanopic DER is 42%
higher compared to standard LED spectrum. There isno change in visual color impression and visual light
output (4000K, CRI>80, R9>50). This graph shows
the spectra of standard LED (white line) and the new
BioUp (black line). The peak in the cyan wavelength isclearly visible.
380420460 480 500

540

580

620

660

700

740

780

Wavelength in nm

Figure 3: Spectral power distribution of a standard 4000K LED source(white line) and the one in Philips BioUp (black line)

Finding the right balance

Countless opportunities

Using optical design to improve lighting distribution
can also contribute to eye comfort by increasing theratio between light that lands on vertical and horizontal
surfaces. When this is combined with Philips BioUp
technology, LEDs can provide biological active lightthat enhances light-related workplace satisfaction andcreates a connection with the dynamics of natural light.

As pioneers in this new era of light for wellbeing, webelieve a whole host of opportunities are about toopen up for human-centric lighting. Philips solution
can transform light from a means to see things better,
into a powerful way to maintain people’s healthand wellbeing, and ultimately their satisfaction andperformance at work.

References
1.

So what’s the best way to achieve that? One way is toincrease the horizontal photopic lux levels on an officedesk to around 1000 lux. But this would need extra
investment and consume twice the amount of energy.
A better way to get more light to fall into the eye isto use spectral tuning and switch to office luminaires
with Philips BioUp technology. This will have the same
benefits as applying higher light levels, while using
less energy, and still activating the ganglion cells andpositively affecting circadian rhythm.
Philips PowerBalance with BioUp technology is aquality office luminaire solution that can help you
achieve that:• Neutral white color temperature, common in officeapplications• CRI >80, R9>50• Biological active light with a high melanopic DER(+42% compared to standard LED spectrum)• Activation closer to natural daylight spectrum• Conforms to office standards like LEED and BREEAM• Helps to attain at least 4 WELL points for lighting.

To find out more about unlocking the power ofhuman-centric light for your business, contact
your local Philips representative or visit online.

https://decision-wise.com/show-me-the-money-the-roi-ofemployeeengagement

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