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Artificial Light & Sleep

An advance note – Chris Kresser did a blog post on this issue on 23/2/13… Not copying, I promise, have been working on this post for a little while and have been interested in this issue for a very long time.

(goddamn you Chris Kresser for making me look like a copy cat!!! :-) )


A little background about me, I still work a day job, I work in engineering and I am variously responsible for the engineering decisions related to sustainability and energy efficiency across close to $20BN of commercial and retail properties. So given that lights consume energy I have picked up a thing or two about them (in fact I have even run visual comfort studies leading to one of the big four banks spending big bucks on upgrading all of their call centre lights). My dream is that I can take this skill set and mold it into upgrading buildings to be wellness promoting rather than being a stressor. Anyone who has a common interest gimme a shout and I would love to have a conversation about it. Imagine if you could get healthier just by showing up to work or going to the mall!

What we’re going to cover in this post is:

  • How the characteristics of light impact your physiology beyond your direct visual perception
  • What that means for you in terms of the artificially lit environments that you’re exposing yourself to
  • What are the solutions for your office building?
  • What are the solutions for your house?

At present the field of Indoor Environment Quality and visual comfort have not really focused on the issues in this post - its a very emerging field of investigation. That being said, there are some studies that on this subject a long time ago[1]A pilot study of a special laboratory strain of cancer prone mice (C3H) was conducted to evaluate the stressor effects of the lighting environment on the health and lifespan of the animals. The study was conducted over 2,000 animals and measured the impacts on their lifespan of different visual environments: 

Type of Light

Average Lifespan of C3H Mice

Pink fluorescent

7.5 months

Daylight white fluorescent

8.2 months

Full spectrum plastic filter

15.6 months

Natural outdoor daylight

16.1 months

So while its a study of mice and not humans, its still pretty compelling evidence that your visual environment has the potential to have some pretty deep seated impacts on your wellness. There are a number of possible avenues of artificial light to stress the body, but for this article we’ll focus on the interaction between artificial light and circadian rhythms/sleep quality.

The basics

The human body makes use of various environmental signals to decide how to perform each of its functions. Some of these are subconscious like sudden sounds triggering a release of adrenalin and some of these are conscious like pain telling you to remove yourself from a particular situation. One less obvious one is how your body tells the time. This comes down to the interaction between cortisol, melatonin and your circadian rhythm.

Cortisol[1] and melatonin interact in a diurnal cycle with cortisol levels being highest in the morning/day and melatonin being highest in the evening/night. Cortisol gets you out of bed in the morning and melatonin tucks you into bed in the night. Leaving aside the entrained circadian rhythm, light is the primary signal your body responds to throughout this cycle. Certain types of light suppress melatonin to keep you awake during the day.

Its probably worthwhile providing a bit of background about light itself: If you think about the light that you perceive during sunset versus during the middle of the day, then its pretty apparent that the light has a different colour or tone (the correct term is “colour temperature[2]”). The point is that the light you are seeing at any point in time is the mixture of many different wavelengths. Think about how your TV makes pictures out of RGB, or how you have to use your cold and your hot tap to get the right temperature in your bath.

The complicating factor is that your body responds to particular wavelengths (“colours”) of light. A way to visualise this is through “a spectral power distribution” (SPD) which shows you the wavelength makeup of a light source. Shown below is an example for sunlight. You’ll notice that it’s a fairly even looking distribution across the spectrum (single tailed normal distribution for stats geeks :)

(Examples of sunlight SPD and SPD for different colour temperatures)

Below 530nm wavelength is the key area for impact on melatonin and circadian rhythms.

What’s the problem?

Artificial light hasn’t always been such a problem. Incandescent (filament) lamps actually provide a pretty good replication of the characteristics of natural light. The problem is fluorescent (and LED - think about your computer/tablet/phone screen) lamps and the light that they generate. Before the advent of fluorescent lamps there would have been a much weaker impact on human performance from artificial lighting in the home and workspace. Fluorescent lamps work by running an alternating current through low pressure mercury vapour which through magic (pretty much... actually just joking its really science...) creates light. The light directly generated is primarily in the UV spectrum so the inside of the lamp is coated with phosphors[3] to convert the UV to visible light.

Now as you can probably imagine the conversion from UV to visible light is not perfect. In fact it still leaves the light fairly blue biased. Blue light affects our melatonin remember? Below we’ve got the spectral power distributions for warm and cool fluoro’s which show that even the warmer lamps still have an incredibly undesirable bias towards the blue spectrum.

(“warm” vs “cool” white is like the battle of the less bads)

These graphs are a pretty good way to demonstrate that the light that we’re “seeing” is the sum of its parts rather than a single entity. These distributions are pretty “lumpy” which is not like natural light. If you notice that there are effectively three sets of peaks in the SPD, this is because the tubes have three sets of phosphor coatings on the inside of them (tri-phosphor). One of those peaks is in the area that you least want it…  

From those figures you can see that while both lamps are bad, the warm white is a bit “less bad”. Lighting manufacturers are latching onto the wellness impacts of their products and designing solutions that provide for variable colour temperature lights, some use dual warm and cool fluoro lamps (as per the above warm is a bit “less bad”), some actually use dynamic colour temperature LED[4]. Unfortunately LED isn’t actually that much better, see below for an LED SPD.

(SPD for an anonymous high quality “warm white” LED lamp, still got the “sting in the tail”)

So what you need to be worried about is that:

  • LEDs won’t solve your space lighting problems for your offices or home
  • All of your iPad, laptop and phone screens are LED (or OLED)

This second point means that programs like f.lux[5] can only help you so much. While f.lux helps and we are very strong proponents of it, its not a complete solution and any light (warm or not) coming from your laptop screen is going to have some melatonin suppressing element to it.

What are the options?

During our recent trip to San Francisco we met up with a wellness focused start-up. Like all start-ups they were operating on a sensible budget and had a tenancy in a building that unfortunately had a really poor lighting installation for a number of reasons[6]. So, we sent them a set of recommendations that they should consider for their office which I’ve copied below:

Unfortunately (and it pains me to say this having worked in sustainability and energy efficiency for so long) filament style lamps provide the best lighting environment for visual comfort/wellness. Why unfortunately? Well they use 5x more energy and last 10% as long so there are two strong environmental drivers that challenge them.

Is there a solution? Well yes but its not pretty! Blue blocker glasses will provide the best protection for you while you are at work, and you can also put a filament task lamp on your desk to slightly improve the visual environment. At home, where you have more control over your lighting environment you would want to set yourself up so:

  • Bedrooms and workspaces (home offices) use either filament lamps or low blue LEDs[7] - if you’re going to be up late at night working or reading then this is a high risk issue
  • Transient areas and bathrooms also should use either filament or low blue LED, in case you get up in the middle of the night and go to the bathroom
  • When you’re watching TV late at night or in front of your computer/ipad monitor chuck your blue blocker glasses on and set the TV colour theme to warm

Long term, the next lighting technology to keep an eye on is Organic LED (OLED). Aside from TVs and phones made using this technology there are a range of commercial and residential lighting products being developed. At the time of writing this we couldn’t find much data to be able to validate how much of an improvement this could be but based on our understanding of the technology you can expect at least an incremental improvement.

Has anyone else had experience with these technologies or have their own solutions? Please share in the comments!

OptimOZ now has Blue blocker glasses available in Australia!


[1]J.N. Ott (1973), Health and Light: The Extraordinary Study That Shows How Light Affects Your Health And Emotional Well-being, Ariel Press, USA, ISBN 0-89804-098-1


[1] Despite the demonization of cortisol as being the “stress” hormone, cortisol has important biological functions in healthy individuals. Like with any other hormone the problems come from cortisol dis-regulation.

[2] Colour temperature is given in Kelvin (temperature) and refers to the equivalent light produced by a particular reference metal at that temperature. Low colour temperature (i.e. 3000K) refers to a warm light (think of a blacksmith working on a glowing red piece of steel) whereas a high colour temperature (i.e. 7000K) gives a bluer/”cooler” light. It all gets more complicated when you start thinking about high colour temperature being short wavelength light :-S

[3] Converts UV into different spectrum light and lets just leave it at that for now J

[4] Such as the Philips HUE and various Philips and Osram commercial type lamps.

[5] http://stereopsis.com/flux/

[6] Along with blue dominated spectral profiles you need to be aware of whether your fluoro’s are magnetic or electronically ballasted, do they have a problematic luminance profile (glare), poor colour rendering index…

[7] E.g. https://www.lowbluelights.com/detail.asp?id=99

Leon Wurfel
Leon Wurfel


Co-founder, OptimOZ.com.au