The key to healthy evening light.

You may have heard that blue light at night can impact sleep.  

That includes light from your phone and other screen-based devices. But it also includes the bulbs used to light your home.  

In this article we’ll cover why blue light has this effect, and what kind of light experts recommend you use in the evening for better sleep.

The time you naturally wake up and fall asleep is regulated by your circadian rhythm: an internal, biological clock.  

In addition to your sleep-wake cycle, the circadian rhythm influences almost every part of your body, including the immune and cardiovascular systems, mood, and cognitive performance. 

Humans evolved out of bright days and dark nights to sync our circadian rhythms with the Earth’s day-night cycle. Specialised cells in your eyes, sensitive to blue light, detect subtle changes in sunlight and time the circadian rhythm accordingly. 

But evening exposure to artificial blue light—from home lighting and devices—signals to your circadian rhythm that the sun hasn’t set, disrupting your circadian rhythm and delaying the release of sleep hormones. 

The cells in the eye that signal to the circadian rhythm are only sensitive to a narrow band of visible light, peaking at 490 nm, which is part of the blue spectrum. 

Your body clock relies on exposure to lots of blue light to set the circadian rhythm during the day. But even comparatively small amounts of blue light at night can throw your rhythm out of sync. 

It's no surprise that experts recommend minimising exposure to blue light in the evening¹. 

There are several steps you can take to reduce evening blue light: 

• Dim or switch off unnecessary lights. 
• Switch to warmer colour temperature bulbs in the places you spend your evenings. 
• Use a blue light filter on devices and dim the brightness. 
• Blue light glasses are another way to block out blue light at night without changing a single bulb. But there are a few catches. Read more.