The Problem With Circadian Lighting
How NASA, militaries & consumers are missing the point.
With the continual research and apparent safety profile of red light therapy (photobiomodulation or low level laser therapy) as well as recent discoveries in the fields of circadian biology have carved out a niche for both ‘circadian’ lighting and therapy devices. Countless companies have been forged in the flames of our current understanding of the negative biological effects of artificial light concentrated in the blue portion of the spectrum, as well as the potential positive effects of red light therapies. So much so, that NASA, international militaries and a growing number of consumers have invested in circadian lighting technologies - but are we all missing the point?
In 1998, American neuroscientist Ignacio Provencio and his team discovered a new opsin in the skin cells of African claw frogs. This non-visual photoreceptor was later found in mammalian eyes where they play a role in circadian entrainment; something previous thought achieved through visual photoreceptor (rods and cones).
Named ‘Melanopsin’, due to its discovery in frog skin melanophores, this intrinsically photosensitive retinal pigmented epithelial cell (ipRGC) component has a peak absorption at approximately 479nm (blue spectrum). The interaction with the high-energy photons allows melanopsin to communicate time-of-day information via the suprachiasmatic nucleus (SCN), often referred to as the central circadian clock/timekeeper.
Evolutionarily, it is very easy to see why, given its sensitivity spectra, melanopsin became so critical to the entrainment of the circadian mechanism - high energy photons are only available in any appreciable amount during the day while the Sun is out. There were essentially no exceptions to this rule since before mammals even existed.1 It was essentially a foolproof system of organism-wide regulation; based on the ever-reliable and unchanging light/dark cycles, non-visual photoreceptors like melanopsin could ensure proper signaling as the stimulus for daytime was only available, well… in the daytime. High-energy photons were simply not available in any useful amount once the Sun had set. Gene expression, hormonal fluctuations and various other physiological and psychological systems had robust and reliable environmental signals to curate their active and passive periods.
Accumulating research in the field of circadian rhythms trends reliably towards the idea that more sunlight during the day and less artificial light at night is a robust and broad strategy for overall health. Large-scale studies have shown strong relationships with light exposure habits and local lighting environments are reliable predictors of affective disorders such as depression, PTSD, bipolar disorder, cardiovascular disease and cancer (particularly breast, prostate and colon cancer).
These relationships are so clear that in some countries, women who have developed breast cancer after shift-working have been compensated by the government as this relationship has been seen as causative.2
Denmark has begun compensating dozens of breast cancer sufferers who say their illness was brought on by working night shifts, setting a precedent that could have implications for compensation claims elsewhere in the world.
Danish officials say the move was made following research published at the end of 2007 by the World Health Organisation's specialist cancer research unit which showed that women who work through the night on a regular basis could be more likely to develop cancer.