|Image 1 (uci.edu): There are billions of clocks in our world, but the most important one of all, our biological clock has gained scientific attention only over the past couple of years - a momentous mistake, as scientists are starting to realize.|
Before we get lost in all the complicated details, yet again, let's start out right away by shedding some light (pun intended) at the most obvious, easiest to understand and to a great degree tweakable control parameter of our circadian rhythm: Light!
Sunlight! What do you know about it? And how does it control your circadian rhythm?
|Image 2: Sir Isaac Newton used a prism to make the frequency spectrum (for us, the frequency determines the color of the light) visible|
- intensity, which would be the number of the photons per time unit that's hitting a certain area of retina and
- frequency, which denotes the energetic load each of this photons is carrying (frequency = speed of light / wavelength)
What does blue light say? It says: "Get up, it's a new day!"
|Image 3: Melatonin (blue) is produced in the pineal gland (purple) in the absence of light stimuli (Soc for End. 2011)|
Only over the course of the past two to three decades, however, are we finally beginning to understand that the handy 24/7 availability of "light" at any desired intensity, along with the oftentimes unnoticeable otherness of this light with respect to its spectral composition (see figure 1) may constitute one of the most underrated health risks we are facing in our 24/7 convenience society: Light pollution.
The sentence "most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs" from one of the most recent reviews of the literature on "light pollution" does already tell you something about where we are heading, here. With the impeding disappearance Thomas Edison's good old light bulbs, the 'fire from the ancestral cave', as I would like to phrase it for all paleo lovers out there, is about to be extinguished ... isn't it interesting, by the way, that the discontinuation of the production of classic light bulbs is vindicated by environmental concerns ... but before I am losing sight of the topic at hand, let's rather take a look on how much worse those "modern" lighting systems actually are and what alternatives we have, if we don't want to return into our fire-lit or pitch dark (man-)caves certain people nobody would even know if it were not for the 100% non-paleolithic 24/7 "enlightening" invention of the Internet as yet another one cave... ah, pardon "one size", of course, fits it all solutions the lights from our computer screens are transmitting right into our brains.
|Figure 2: At least for city lights and the like, the energy efficient yellowish sodium vapor lamps could provide some relieve of the nightly "light stress" we are exposed to (data based on Falchi. 2011)|
A call for action: Reduction, revision, regulation?
- take account of existing nighttime lighting habits in order to minimize the impact on human activities
- allow easy identiﬁcation of non-compliant light sources and
- allow easy measurement in the ﬁeld, when needed
- establish a "protected range" within the 440-540nm range of the spectrum that corresponds to the maximum sensitivity of the scotopic vision and will thus have the greatest effect on the natural nocturnal melatonin production
- limit direct light exposure of the eyes by no not allowing luminaries to send any light directly at and above the horizontal
- avoid over lighting, shut off lights when the area is not in use and restrict growth of the total installed ﬂux
In case you agree with my personal assessment, though, and believe that relying on governmental regulation usually produces more problems than it solves, you will be happy to hear that the use of the previously mentioned blindfolds, dark curtains and even the use of blue blocking glasses, as suggested by Dom Leste in response to my recent post on the "1lbs Fat Loss Bonus of 40 Minutes of Additional Sleep", can provide the much needed relief from the melatonin suppressing effect of constant "blue-light" exposure (Sasseville. 2006).
Technologically advanced approaches to nutural circadian rythmicity
|Image 3: F.Lux is probably the most popular program to adapt your screen brightness and hue to the time of the day, but there are alternatives and mobile solutions of which Lux, for example, looks pretty neat.|
So do those programs work? Or do they at least make sense?
Despite the lack of peer-reviewed research on the general, let alone individual effectiveness of these programs, the results of numerous recent publications on the negative effects of non-adaptive screenlight and even regular (undimmed) household illumination, on the natural circadian rhythm would suggest that the use of respective software programs, or simple electronic dimmers could limit well-established detrimental short term effects such as the...
- ... postponement (~2h) and shortening (-90min!) of the nocturnal melatonin expression which occurred in 99% of 112 young healthy subjects who were, just like about everyone who would be sitting in his office in the afternoon and on the couch in front of the telly in the evening, exposed to regular electric room light (constant spectral composition and intensity <200 Lux) for 8h before they went bed (Gooley. 2011)
- ...50%-90% suppression of melatonin, 80% of the people suffer from, when they accidentally or deliberately try to switch from one to another sleeping rhythm by simply not switching the light out and staying up late (Gooley. 2011)
- ... significantly more pronounced suppression of melatonin production of computer, laptop, mobile devices and TVs with LED displays as compared to the old-fashioned CCFL backlit displays (Bues. 2012)
Don't worry, you don't have to reside in paleolithic darkness - thanks to neolithic science!
For the rest of you, I have already outlined a couple of easily implementable strategies to avoid the negative aspects of artificial light exposure, where the light (artificial or not) is not a necessary or desirable part of your life (blindfolds, curtains, special light sources, computer software, orange blue-blocking glasses, keeping the lights low, dimmers, etc.; check out my previous blogpost "1lbs Fat Loss Bonus of 40 Minutes of Additional Sleep", as well).
I for my part am now enjoying the sunlight for maximal melatonin suppression, cognitive and physical performance and a powerful signal to my circadian clock that she is still accurate and would suggest you do the same - unless you want to leave me some feedback on this first installment of the Circadian Rhythmicity Series and where you want it to be heading, of course!
- American Medical Association (AMA), House of Delegates. Resolution 516 e Advocating and Support for Light Pollution Control Efforts and Glare Reduction for Both Public Safety and Energy Savings. 2009.
- Bues M, Pross A, Stefani O, Frey S, Anders D, Späti J, Wirz-Justice A, Mager R, Cajochen C. LED-backlit computer screens influence our biological clock and keep us more awake. Journal of the Society for Information Display. 2012; 20: 266–272.
- Bukalev AV, Vinogradova IA, Zabezhinskiĭ MA, Semenchenko AV, Anisimov VN. Light pollution increases morbidity and mortality rate from different causes in male rats. Adv Gerontol. 2012; 25(1):49-56.
- Cajochen C, Frey S, Anders D, Späti J, Bues M, Pross A, Mager R, Wirz-Justice A, Stefani O. Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance. J Appl Physiol. 2011 May;110(5):1432-8. Epub 2011 Mar 17.
- Falchi F, Cinzano P, Elvidge CD, Keith DM, Haim A. Limiting the impact of light pollution on human health, environment and stellar visibility. J Environ Manage. 2011 Oct;92(10):2714-22.
- Froy O. Metabolism and circadian rhythms--implications for obesity. Endocr Rev. 2010 Feb;31(1):1-24.
- Gooley JJ, Chamberlain K, Smith KA, Khalsa SB, Rajaratnam SM, Van Reen E, Zeitzer JM, Czeisler CA, Lockley SW. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab. 2011 Mar;96(3):E463-72.
- Hollan J. Metabolism-inﬂuencing light: measurement by digital cameras, Poster at Cancer and Rhythm Oct 14-16, 2004, Graz, Austria.
- Sasseville A, Paquet N, Sévigny J, Hébert M. Blue blocker glasses impede the capacity of bright light to suppress melatonin production. J Pineal Res. 2006 Aug;41(1):73-8.
- Soc for End. "Melatonin" in Glosarry. 2011 March < http://www.yourhormones.info/hormones/melatonin.aspx > visited 2012 Aug 05.
- UCI.edu. Illustration to article "The Clock Watcher". < http://www.uci.edu/features/2009/05/feature_circadian_090528.html > visited 2012 Aug 05.
- Wood B, Rea MS, Plitnick B, Figueiro MG. Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression. Appl Ergon. 2012 Jul 29.