What Colors of Artificial Light Affect Sleep?

There are a lot of articles out in the public domain which argue how much artificial light your blue blockers should be blocking.

Some state that you only need to block 50% blue, others all blue and some are even suggesting green light needs to be blocked.

So let’s take a look at the information available and determine how much and what spectrum of light should be blocked for optimal melatonin production.

Artificial Light After Dark Suppresses Melatonin Production

In the year 2000 a study by Jamie Zeitzer et al determined that exposure to intense levels of artificial light during the darkness hours phase shifted circadian rhythms.

23 volunteers took part in a nine day experiment whereby they were exposed to artificial light for 6.5 hours prior to bed. The results concluded that dim light before bed had little effect on melatonin production whereas bright room light of high luminance completely suppressed melatonin production.

This would either create serious sleep disorders or create a circadian phase shift, meaning natural sleep times were pushed back to later in the night. The brain, when exposure to artificial light perceives the day to be longer, night time starting later and the dark hours being shorter.

In 2011, Gooley et al published a study also showing that exposure to room light before bedtime suppresses melatonin onset and shortens melatonin secretion duration. This provides further evidence that artificial light needs to be blocked before bed. We seem to be darkness deprived in modern day society.

Blue Light After Dark Suppresses Melatonin

The light from digital devices and LED lights in our homes emit short wavelength enriched artificial light.

What this means is the blue frequencies are higher in concentration than natural light. Blue frequencies from 380-500nm can be classified as short wavelength light. This coincides with Zeizer’s experiment where higher concentration of artificial light seems to evoke the most suppression of melatonin production. 

As we can see from the graph above, the biggest difference between natural sunlight and artificial LED light is the sharp spike in blue light around the 450nm wavelength.

In order to allow melatonin secretion we need to address this spike in blue, blue blockers with an amber lens will block the blue light so the spike pictured above disappears after dark.

In 2009 Burkhart & Phelps. published a study looking to analyse blue light blocking after dark on melatonin production. They took 20 adult volunteers and were split into two random groups where one wore amber tinted lenses before bed and the remaining participants wore yellow lenses before bed. At the end of this experiment the data showed that the participants that wore the amber lens glasses had a significantly better sleep quality and duration than the yellow tinted glasses.

Burkhart & Phelps coin a fantastic statement “blocking blue light could create a form of physiologic darkness.”

Blue light after dark must be blocked in order to increase melatonin production, improve sleep quality, advance circadian phases and also improve health issues such as depression and anxiety.

Orange and amber lens glasses block between 90-100% of blue light, as a minimum one should be wearing amber glasses before bed time to block sleep disrupting artificial blue light. As a rule of thumb the darker the amber tint the more blue light will be blocked.

Green Light After Dark Suppresses Melatonin

It is conclusive that artificial blue light exposure after dark disrupts sleep cycles. Excellent studies have been released that prove this point and there are many more to be found on pubmed. However, there is increasing talk in the biohacking communities that some green light can also suppress melatonin production.

In 2001, Wright and Lack released a paper analysing different light wavelengths and their effect on melatonin production, when exposed after dark.

They compared 660 nm (red), 595 nm (amber), 525 nm (green), 497 nm (blue/green), and 470 nm (blue) wavelengths.

The shorter wavelengths, 470, 497 and 525nm showed the greatest melatonin suppression, 65% to 81%. The shorter wavelengths also showed the greatest circadian phase delay ranging from 27-36 minutes (in essence exposure of these frequencies of light delayed the participants falling asleep).

In 1991 a study emerged in Sleep by Horne et al. which showed that green light from 500-530nm suppresses melatonin.

In 2010, Gooley showed that green light close to the 550nm spectrum has a similar effect on suppressing melatonin as that of blue light. However during the light exposure the spectral sensitivity to the green light decayed exponentially relative to the 460nm blue light.

Green light exposure before bed seems to have a similar effect on melatonin suppression as that of blue light.

Green spectrum light from 500-550nm has a varying effect on suppressing melatonin before bed from what the literature is showing.

What Light Did Our Ancestors See After Dark?

Prior to bed the concentration of light our ancestors would have seen would have been red and orange.

As the sun sets these colours become more visible and are the last colours we see before bed.

Our ancestors would have had access to camp fires to keep warm and the light emitted by fires is red and orange. As we have shown from the literature short wavelength light (380-550) blocks melatonin production and longer wavelength light has no impact (555-700).

How Much Artificial Light Should We Block

The literature clearly shows the blue and green light need to be blocked before sleep in order to maximise melatonin production. Blocking blue is a minimum and will improve your sleep, but blocking blue and green will be optimal for those looking for optimization. Studies have shown varying results from green light, for instance some show blocking up to 525nm, 530nm, near to 550nm.

People who are wearing yellow lenses or clear lenses after dark are clearly not going to reap any benefits. Those types of glasses are great for mitigating digital eye strain and should not be marketed as blue blockers.

BLUblox Sleep+ lenses have been designed with the above science in mind and block 100% from 400-550nm.

Click here to see the SLEEP+ Range.

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