Darkness Is a Human Need: What a Study of 11,071 People Tells Us About Light at Night
Can a little light at night change your heart?
A new study of 11,071 people suggests it can, and the amount of light involved is far smaller than most of us would ever notice.
What the study measured
Participants wore light sensors on their wrists for a week to measure how much light reached them at night. About three years later, they underwent cardiac MRI scans so researchers could examine the structure and function of their hearts.
What does three lux look like?
Three lux is roughly the low glow that might reach the bed from a very dim nightlight or light spilling through a doorway. Yet it is approximately 1,500 times brighter than a clear, moonless, starlit night.
What this means for you, and for designers
- Tonight, lie in bed with the lights off and notice every glow that reaches you.
- Cover or remove standby lights on chargers and electronics.
- Add blackout shades to your current window treatments. You don’t have to replace what you already love. For custom shades and draperies, ask an Exciting Windows! design specialist.
- My favorite: remote-controlled shades, now available wireless, so you can close out the light without leaving the bed. Lutron makes them, and your Exciting Windows! specialist can help you choose them.
- Consider circadian smart lighting that shifts warmer and dimmer in the evening. Lutron makes these systems too. For lighting design, work with a lighting designer such as Adaptive Design Group.
- Design the nighttime journey as carefully as the daytime experience.
- Give people enough light to move safely and find what they need, without flooding the bedroom.
- Shield light sources and control light spill from hallways, bathrooms, and devices.
- Provide true darkness at the bed.
Why the small things matter
An association between measured nighttime light exposure and measurable changes in the heart across more than 11,000 people is not something any of us, including architects and designers, can responsibly wave away.
“The small design elements add up, day after day and night after night.”
They shape our bodies, health and behavior – even our outcomes – for worse or for better.
Light from a hallway, bathroom, device, or adjoining room may seem insignificant. But night after night, the body works against it, and good design can lighten that load.
Darkness is a human need
We have long understood the body’s need for properly timed light. Properly timed darkness matters just as much. It is one of the 16 Human Needs of the Built Environment, and this study brings it into measurable focus.
Darkness makes restorative sleep possible, and restorative sleep supports everything else: how we function by day, and the repair that sustains health and longevity. When we remove stress from the body, it naturally regenerates. That is “youthing.”
So the question for every bedroom we design: does it let the body do what it needs to do at night?