Insomnia: The Impact of Artificial Light

Dr. Colin Lemmon

Insomnia Series

Blue Light, Green Light and Red Light

Our patterns of sleep are governed by the circadian rhythms which regulate our system and keep us in sync with the natural cycles of day and night. When the light fades of an evening, our eyes and skin detect the change, sending a signal to the pineal gland to release melatonin which triggers tiredness and the onset of sleep. When the first rays of dawn seep in through the window, we detect the subtle change and the pineal gland abruptly reduces the melatonin to wake us ready for the day ahead.

Under natural conditions, the sleep cycle begins between 8pm and 10pm depending on the time that sunset occurs and the length of twilight (which is far longer close to the equator).  However, in modern society, this cycle is delayed or interrupted by the UV, blue and green light emitted by artificial lighting and electronic displays. These components of light (at the higher end of the light spectrum) simulate daylight which suppresses melatonin and delays the natural onset of sleep. If we turn lights on in the middle of the night for even a minute, we can disrupt or reset our circadian rhythms and throw our biological clock out of whack with devastating results.

Interestingly, humans have over a long period of time conditioned themselves to stay awake by the red glow of a fire. As a result, we have adapted to red light (at the lower end of the light spectrum) which has little or no effect on the release of melatonin and therefore does not delay the onset of sleep.

Blue light is at the top of the visible light spectrum and has the greatest impact on melatonin production. Green is the next highest color and has a lesser effect.

House lighting

As much as people are moving towards energy efficient LED globes, these globes have significantly higher levels of blue and green light. The dull yellow glow of an old style filament bulb is better in this regard.

A lamp with a shade and a low power filament bulbs will keep the light diffused and indirect which will soften the ambience of an evening. My wife used a small lamp with a filament bulb and a tea towel over the top when she got up to each of our four children through the night. This may be part of the reason she did not suffer tiredness or the effects of post-natal depression.

Eliminating Blue Light Only

An alternative to normal light bulbs is the Good Night bulb by Lighting Science which was originally developed for NASA to help the astronauts sleep on the International Space Station. This bulb provides a white light while filtering out the unwanted blue light.

If you do not have control over the lighting in the house you can consider amber tinted glasses, which filter out blue light.

Eliminating Blue and Green Light

Although green light contributes less than blue to the suppression of melatonin, some suggest it should also be removed. A red LED night light or dimmable red LED light bulbs can be used to remove both the blue and green components. However, red light produces a similar ambience to that of a photographic dark room which some people find unnatural.


I find it essential to open the curtains and wake at dawn to natural sunlight. Do not ever think that more sleep means waking more refreshed (see Snoozers, are in Fact, Losers).

Electronic Displays

The blue and green light emitted by electronic displays has a similar effect to sunlight. Free software such as f.lux will automatically filter the blue (and optionally the green) light from your display between dusk and dawn.

Currently I run my computer using f.lux with the setting between Ember (reddish tinged screen) and Dim Incandescent (yellow tinged screen) with the brightness turned down.

It is also important to reduce the brightness of your electronic devices. Computers, laptops, eReaders, tablets and phones all have brightness controls. If the brightness control is hard to find on your computer, f.lux provides hot keys (Alt + Page Up and Alt + Page Down) to adjust the brightness.

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