Interim NIOSH Training for Emergency Responders: Reducing Risks Associated with Long Work Hours

The Color of the Light Affects the Circadian Rhythms
a laptop, tablet, and two mobile phones
  • Blue light has the strongest impact. Exposure to blue light (and white light, which contains blue light) during the sensitive period can make it difficult for you to fall asleep and stay asleep.
  • Exposure to white light during the day can have positive effects, including boosting alertness and mood.
  • Red light has no effect on the circadian clock, so you can use a dim red light at night.
  • Yellow and orange light have little effect on the clock so you can use a very dim yellow or orange light at night.

Blue light waves come from fluorescent and LED lights and back-lit electronic screens on televisions, computers, tablets, and cell phones. Remember, exposure to these lighted screens during the sensitive period can make it difficult for you to fall asleep at night or can wake you up too early. Especially if you are having trouble with sleep, avoid these lights during the sensitive period.

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Page last reviewed: April 1, 2020