Use of LED Lamps To Improve Health

Today’s New York Times has an article on several manufacturers’ new LED products that are intended to improve wakefulness, sleep, focus, and other aspects of daily life and health. The article appears on both the business and technology pages, but not on the health page, and I think that’s appropriate.  Although there are testimonials by the consumers of some of these products, there’s no discussion about any peer reviewed science behind them.  In fact, about two-thirds of the way through the article the author finally gets to the fact that, “Researchers are still determining how spectrum and intensity of light affect the brain.”  So, the article is an uncritical look at new LED products that make health claims.  We shouldn’t rely only on the claims of the manufacturers, though – remember the claims of 100,000 hour lifetimes for LED lamps?

I’m not saying that we know nothing about how light affects us, because we know quite a bit.  The question is, “Do we know enough to properly and safely integrate that information into our design practice?” and there things become uncertain.  So, before accepting the claims of manufacturers, or making the same claims to clients, it’s important for designers to be up to date on the current state of research and to understand the strength of the findings, as well as how (and if) those findings can be folded into a design.

There are a few web sites that I find useful for keeping up to date.  The first is the Health and Vision page of the Lighting Research Center’s web site, which has links to many of their recently published research papers.  The second is the Research page of USAI Lighting’s web site.  This page provides links to a mix of newspaper articles and scholarly publications on a variety of topics connected to LED lighting.  The third is the Research page of the IES web site.  Finally, members if the IES can  download copies of Leucos, and non-members can purchase copies.

LEDs continue to revolutionize the lighting industry.  Most manufacturers have ended  research and development for incandescent and fluorescent products. OLEDs are increasing in efficacy and prices are dropping, while new technologies (such as light emitting plasma and quantum dots) are on the horizon or already here. To preserve their client’s money, the occupant’s health and safety, and their own reputations, designers need to make sure that they don’t get swept up in the possibilities that are marketed to them before the facts are in.

Light & Health Seminar

The New York City chapter of the IES will host a presentation by Mariana Figueiro and Leora Radetsky of the Lighting Research Center titled “Swimming in an Ocean of Light: Using Light for Health and Well-being.”  The program will include the IES Light and Health seminar, which they co-authored, as well as updated material with recent research results and their insights about “turning research into design practice.”

If you’re interested you can RSVP here.

Circadian Lighting

A recent article in The Wall Street Journal discussed the possibilities and benefits of lighting systems that shift color to mimic the changes in daylight. It’s a complicated subject so it’s not surprising that some of what’s reported is inaccurate, so let me clarify a few things.

First, our current understanding of how light affects our circadian rhythms is that a light activates a type of cell in the retina called intrinsically photosensitive retinal ganglion cells (ipRGC). These cells, unlike rods and cones, are unrelated to vision. The signal they send to the brain is received by the suprachiasmatic nucleus (SCN), which is the body’s hormone regulator. As the graph below illustrates, the ipRGCs are most sensitive to short wavelength (blue) light and, unlike rods and cones, are unaffected by long wavelength (red) light. (A more detailed explanation can be found in Chapter 16 of Designing With Light, and in this article from the Journal of Circadian Rhythms.)

 

ipRGC (black), rod (blue), and cone (red) sensitivity curves
ipRGC (black), rod (blue), and cone (red) sensitivity curves

 

The ipRGCs signal to the SCN, which keeps our circadian rhythms are kept in sync with the day/night cycle, seems to be affected by three factors: color balance; intensity; timing. Cool (bluish) light should be delivered at a relatively high brightness in the morning hours. Delivering cool light in the evening hours can disrupt sleep and other processes controlled by the SCN.

Next, there’s nothing special about LED lighting that makes it uniquely appropriate for this application. Fluorescent, HID, and incandescent light (adjusted with color filters) can all be used to create a system that delivers cool light in the morning and warm light in the evening. In all cases, this involves the use of light sources of several tints (warm, cool, and possibly neutral) that are individually controlled. The WSJ is completely wrong when it says “unlike incandescent or fluorescent lights, LED lights’ materials and electronic components allow for finer adjustments of color, brightness and intensity.” A single LED creates light of a single color. To shift colors a second LED is required. Brightness and intensity are the same thing. With LEDs set to surpass sales of all other light sources within the next several years, research involving sources other than LED is nearly non-existent. Naturally, researchers are using LEDs to test theories and to develop demonstrations and products.

Finally, it would be helpful if the WSJ had defined two terms – color temperature and CRI (Color Rendering Index). Both are explained in Chapter 8. Color rendering and CRI are briefly explained in this post. CRI and color temperature are both addressed in this post.

Light and Health

The DOE has recently published a fact sheet titled Lighting for Health: LEDs in the New Age of Illumination.   It summarizes the Trends in Neuroscience January 2014 article Measuring and Using Light in the Melanopsin Age.  Both publications explain the current understanding of our visual and nonvisual response to light.

The basics of our visual response to light is understood by everyone – it gives us the ability to see.  The nonvisual response is less known generally, and is still being researched by scientists across the globe.  This is discussed in my book in Chapter 16 Light and Health.  What we have learned in the past two decades is that there is a third type of light sensitive cell in our eyes (the first two being rods and cones) called the intrinsically photosensitive retinal ganglion cell (ipRGC).  When light strikes the ipRGC a pigment called melanopsin breaks down, sending a signal to the brain.  That signal doesn’t go to the visual cortex, however, but to the suprachiasmatic nucleus (SCN) the body’s timekeeper.  The SCN regulates circadian rhythms and the production of hormones affecting alertness, heart rate, blood pressure, stress response, and more.  The SCN is reset by information from the ipRGCs.  Simple exposure to light, though, is not enough. The exposure time of day, duration, and wavelengths all contribute to proper synchronization. SCN regulation seems to be maintained by high brightness, short wavelength light in the morning (i.e., morning daylight). If appropriate stimulation does not occur, the timing signals for hormone production can become desynchronized. It is known that circadian desynchronization plays a roll in insomnia, mood, depression, reaction time, creativity, and alertness. It is suspected that this desynchronization also plays a roll in cancer, diabetes, dementia, and cardiovascular disease.

This has lead to some talk of light as a drug that controls the SCN.  At this point it is probably premature to attempt to apply this information in most lighting designs because most spaces have a wide range of users with a similarly wide range of needs.  A lighting design for the overnight shift, for example, may not work well for the day shift.  There are a few rules of thumb that can be applied in specific circumstances.  For example, a designer can minimize the nonvisual circadian response by limiting the amount of light, especially short wavelength light, reaching the eye.  However, the science is still in the early days and the specifics about the effect of light level, spectral distribution, and timing on users and for various applications are not clear.