Over four million years of evolution, the cycle of day and night has shaped human beings. The 24-hour recurring pattern of light and dark stimulates our body’s processes, when we sleep and when we wake. This daily cycle, known as our ‘circadian rhythm’, is driven by natural light which triggers hormonal changes within the body.

Studies have shown that the blue-white light found in morning sunlight suppresses our sleep hormone, melatonin, and causes the production of the stimulating hormone serotonin. Warm-red light found in evening sunlight increases melatonin production which makes us feel tired and encourages sleep.

Indoor living

Since we now spend 90% of our time indoors, we don’t receive enough exposure to natural light to stabilise our circadian rhythm. The artificial lights found in many of today’s buildings contain high levels of blue light which stimulates activity. Exposure to this constantly, each and every day, affects our hormone production and disrupts our circadian rhythm.

To see this effect in action, use your phone just before bed. It makes you feel awake. For this reason, most phones now have a ‘Night Shift’ mode which adjusts the colour temperature of your screen. Instead of a crisp, blue-white light, the screen has a more warm-red tint that’s less stimulating during the hours when your body should be preparing for sleep.

The buildings we live and work in can have a huge effect on our health and wellbeing. We spend most of our days at work so our offices have a proportionately high impact on how we feel, act and sleep.

Initiatives such as the WELL Building Standard have therefore recently been introduced to measure the performance of buildings against some crucial factors that affect human health. WELL specifically measures seven factors; air, water, nourishment, light, fitness, comfort and mind. After the basic human requirements, light is emphasised as the most important influencer. This growing awareness of the impact of natural light has driven the concept of human centric lighting and a need to ensure people receive exposure to daylight despite spending less time outside.

Biologically-effective light

Human centric lighting ensures that the right type of light is available in a space at the right time. Natural daylight is the ideal source of light and should be incorporated into the built environment as much as possible. When artificial light is unavoidable, using biologically-effective light which can replicate the changes in sunlight throughout the day supports a healthy environment.

Modern LED lights can almost completely represent the colour spectrum of sunlight, replicating red and blue light at a kelvin range of between 2700 and 6500. The award-winning Sleep Research and Clinical Chronobiology research group explored the effect of such light on humans in collaboration with Psychiatrist, Dr. Dieter Kunz. The clinical study, conducted in Berlin, used LUCTRA luminaries to prove the biological effect of light on humans. LUCTRA luminaires provide a wide kelvin range and generate illuminance of up to 1000 lux through four high-performance CREE LEDs, enabling the researchers to test the impact of different types of light.

Given the human reaction to light demonstrated by the study, biologically-effective lights can be used as part of a human centric lighting scheme to replicate the effects of natural daylight. Yet, despite these positive findings, there has been no revolution in the workplace to change existing lighting schemes. “Most of the lighting currently available is detrimental to health,” argues Dr. Kunz. Clearly, more can be done to use these findings in the design of the built environment and support buildings to achieve WELL certification.

Individualising light

We are all unique. We work different hours and carry out different tasks. Where large numbers of people are found in close proximity, localised lighting gives each individual the ability to adjust their light exposure according to their own personal needs.

“The control of modern lighting systems is being discussed intensively,” explains Ulrich Kuipers, Professor of Electrical Engineering and IT at the University of Applied Sciences in Germany.

“Standardisation is a huge obstacle and we should be looking more to develop intelligent lighting control systems.”

One such solution is the use of task lighting alongside natural daylight and overhead lighting to ensure that an individual’s workspace is illuminated to their required level.

Kuipers is responsible for the technical development of LUCTRA, LED luminaires which give each user control of the light colour and intensity either through a touch panel or an app. The specially designed app connects to the luminaire via Bluetooth and can also be used to set a personalised lighting sequence which automatically changes throughout the course of the day. “The luminaire will alter its light colour and intensity without you even noticing the changes,” explains Sean Starkey, Managing Director of Durable UK, the manufacturer of LUCTRA. “This automation reduces the need for the user to actively alter their luminaire, but it is also possible to override the sequence as we know our working patterns in the modern age can shift from day to day.”

Lighting for the future

Disturbances to our circadian rhythm can have serious consequences on our wellbeing and performance in the short term and our overall health in the long term. Human centric lighting is the key factor that stimulates and stabilises our inner rhythm. It can combat insomnia, irritability and a lack of concentration and promote alertness, higher activity levels and restful sleep at night.

Putting humans at the heart of design will give us spaces that put people and their individual needs first. There is a growing awareness of the important contribution of light to healthy living, so we will see more spaces that are lit by natural daylight or biologically-effective lighting. These are spaces that will support the levels outlined in the WELL Building Standard. Spaces that will cater for our basic individual needs.