How different colors of evening light affect melatonin, alertness, and sleep

Control-adjusted melatonin suppression was significantly reduced with blue-depleted LED light compared to standard fluorescent light.

• Sixteen healthy participants were exposed to two different light sources for 8 hours prior to bedtime in a controlled setting.
• Subjective sleepiness did not differ between the blue-depleted LED light and standard fluorescent light conditions.
• Auditory reaction times were significantly slower under blue-depleted LED light compared to fluorescent light 30 minutes before bedtime.
• EEG measurements indicated reduced alertness under blue-depleted LED light, demonstrated by increased spectral power in the delta-theta frequency range.
• No significant differences were found in total sleep time, sleep efficiency, or slow-wave activity between the two light conditions.
• An order effect on sleep variables was noted, with participants receiving blue-depleted LED light first showing increased total sleep time, sleep efficiency, and slow-wave activity.

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