Article at a Glance:
- Humans have long relied on the sun’s energy as well as fire and candlelight for illumination; however, we now have other technologies that allow us to stay up later into the evenings.
- Modern technology has led to fluorescents, LEDs, and an ever-growing array of digital devices with LED screens.
- More time indoors means more time exposed to artificial lighting, which directly impacts circadian rhythms and sleep patterns.
- The human body needs warmer (redder) lighting in the hours leading up to bedtime as the wavelengths in the red light spectrum are closest to the wavelengths emitted by the sun during sunset.
- In contrast to short blue light wavelengths that suppress melatonin production, warm red light is better suited specifically for evening hours because it helps the body produce more melatonin (the sleep hormone).
Centuries ago, our ancestors relied solely upon the sun and fire to illuminate the space around them. This was conducive was regulating their circadian rhythms naturally. Conversely, modern technology has pushed society indoors, which means more exposure to junk light and chronic sleep problems. Too much light, especially at night time, prevents your body from producing melatonin naturally, which, in turn, makes it more difficult to fall and stay asleep. Redder (warmer) lighting is more appropriate to use in the hours leading up to bedtime because it is closer to the natural light spectra at dusk. This lighting promoted better, deeper sleep.
How Light Influences Your Sleep
Your body perceives light and darkness through the eyes, which contain blue-light-sensitive cells called intrinsically photosensitive retinal ganglion cells, or ipRGCs. These cells are directly responsible for communicating how bright it is in the environment to the brain’s master clock. So, it’s no coincidence that humans systematically rest at night when it is dark outside. As the sun descends below the horizon each evening, the color temperature of the sky changes accordingly, and your body begins to produce melatonin – the key ingredient (hormone) for falling and staying asleep. Resting in a cave-like environment (like our ancestors used to) is essential for helping the body wind down and recover overnight.
How the Lighting Revolution Has Affected the Way We Sleep
For many centuries, humans relied on candlelight at night. Then came the development of incandescent bulbs. These light sources emit “warmer” light (reddish in color), which is conducive to illuminating the space at night around you without affecting your sleep.
Today, we not only have new advances in lighting technology (thanks to fluorescent and LED bulbs), but we also have greater exposure to it. In fact, many people — labeled as the “Indoor Generation” — spend as much as 90% of their time indoors under artificial lighting and/or using digital devices with LED screens. These light sources emit “cooler” light (bluer in color) that mimics daylight when the sun is at its highest point in the sky. Given that blue light promotes alertness, exposure to blue wavelengths at night is not ideal.
See the chart below which shows the spectrums of different light sources:
Light and Sleep: The Bottom Line
“Lights out!” at night isn’t just a pastime; it is necessary for regulating your circadian rhythm and hormones. In a world where the lights are always on, it’s important to be mindful of their color temperature and brightness, especially in the hours leading up to bedtime. With that said, red light is an appropriate option for those that need to get up in the middle of the night.