A–Z Glossary

Blue light

Blue light is a short-wavelength light from screens and some bulbs that can signal the brain to stay awake and delay sleep.

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Blue light and sleep impact

Blue light and sleep impact

How blue light affects the sleep-wake system Blue light is the short-wavelength end of the visible spectrum. It is not inherently harmful in daytime; in fact, natural morning light helps anchor circadian timing and supports alertness. The issue arises when blue-enriched light is delivered late in the evening, after the brain has started to prepare […]