Good Light Is Not Just About Seeing Better, It's About Sleeping Better
When most people think about lighting, they think about vision. We switch on a lamp to read a book, illuminate a workspace or make a room feel cosy. For more than a century, lighting has been designed primarily to help us see better. But science has revealed that light does far more than illuminate our surroundings.
It also tells our body when to be awake and when to prepare for sleep.
In other words, good light isn't only about seeing better, it's also about sleeping better.
Light is the body's most powerful clock
Every cell in your body follows a roughly 24-hour rhythm, known as the circadian rhythm.This internal timing system regulates much more than sleep. It influences alertness, hormone production, body temperature, metabolism, digestion and even your mood and energy.
To stay synchronised with the outside world, your biological clock depends on one signal above all others: Light.
Every morning, the light entering your eyes tells your brain that a new day has begun. As daylight increases, your body becomes more alert.
As evening falls and light levels decrease, the opposite happens and the dim light shows your body it’s time to prepare for a restful night's sleep.
Your eyes don't just see, they tell time
For many years, scientists believed the eye had only one purpose: vision.
Research over the past two decades has shown that the eye has another crucial role beyond vision.
Specialised light-sensitive cells in the retina, scientifically known as ipRGCs, continuously measure the timing and spectrum composition of light around us. For simplicity, we call these cells ‘spheres’. These cells don't create images. Instead, they send information directly to the brain's master biological clock, allowing your body to distinguish between day and night.
Every glance out of a window, every walk outdoors and the kind of light in which you spent every evening influences this system.
Bright days and dark nights lead to better nights
Healthy sleep begins with the light your eyes receive during the day. Receiving plenty of bright daylight during the morning and throughout the day strengthens your biological clock. A well-synchronised clock makes it easier to become alert during the day and sleepy at night.
Spend at least two hours a day in daylight or under electric lighting that provides at least 500 lux at eye level. During the three hours before bedtime, keep light levels below 10 lux. At night, keep light levels below 1 lux and avoid screens whenever possible.
Sleep doesn't begin when you get into bed. It begins with the light your eyes receive throughout the day.
Modern life has reversed nature
Humans evolved under an environment with bright daylight, gradually darkening evenings and dark nights.
Modern life often looks very different. Many of us spend our days indoors under relatively dim lighting before returning home to brightly lit living rooms, televisions, smartphones and tablets. From the perspective of our biological clock, this sends mixed messages.
Our days are often too dim, while our evenings are too bright.This weaker distinction between day and night can make it more difficult for the body to recognise when it should be awake and when it should prepare for sleep.
The strongest circadian rhythm comes from creating a clear contrast: Bright days. Dark nights.
Good light means the right light at the right time
The benefits of good light and a well-aligned circadian rhythm include: better sleep, more energy, a more positive mood, sharper concentration, and better overall health.
Does this lighting support human health?
Offices, schools, hospitals, care homes and homes themselves are beginning to recognise that lighting should support not only visual performance, but also sleep, wellbeing and long-term health.
This shift marks a new era in lighting design, one where human biology becomes just as important as energy efficiency or aesthetics.
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