The circadian rhythm regulates a number of biochemical, physiological, and behavioural processes. One of the most important bodily functions regulated by circadian rhythms is the sleep and wake cycle. During the day we are awake and alert but as the sun begins to go down melatonin is produced to help prepare us for sleep.
As much as the development of LEDs is a great technological achievement for energy efficiency, it has also a downside effect as the blue/cool light of LEDs can delay the release of melatonin as we prepare for bedtime, thus affecting our sleep cycle. Blue or cool colour temperature LED light has twice the harmful impact on night-time melatonin release when compared to warm white incandescent light, even when the lux intensity is matched. Even a hint of dimmed light, 8 to 10 lux, can affect our sleep during the night, so we can imagine the effect of a standard bedside lamp which can produce 20 to 80 lux.