NIOSH Training for Nurses on Shift Work and Long Work Hours

The Color of the Light Affects Circadian Rhythms

• Blue light has the strongest impact on circadian rhythms.^26,27 White light is composed of visible light color waves from violet to blue, green, yellow, orange, and red. Exposing the eyes to blue light (or white light, which includes blue light) during the sensitive periods triggers photoreceptors in the retina to send a signal to suppress melatonin and shift circadian rhythms.
• These photoreceptors do not respond to red light and minimally respond to yellow and orange light.
• Exposure to white light during the daytime can have positive effects including boosting alertness and mood.

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.