The Pseudo Science Marketing of Human Centrcity

Posted: June 10, 2017 in General Commentary

Full disclosure

I do not use, like, or support, the term “Human-Centric Lighting” or HCL, and the marketing of it. Nor am I convinced the bullish marketing of the term makes it any more attractive or legitimate. The term has been tagged onto so many crack-pot claims, unsupported promises, and misapplication of hand-selected, overly simplified misleading single-line extractions from legitimate studies, and anecdotal claims by unqualified “experts” – that it has become nothing more than an extension of the now discredited “Full Spectrum” marketing that has plagued lighting for decades. The confusion of white light tuning for lighting color effect has now been bolted to human-centric lighting, as more and more marketers rush to stake a claim on this populist movement. I am weary of the numerous “studies” supporting claims, that are nothing more than simple biased surveys of lighting customers, with no effort to remove the Hawthorne Effect, or other bias, that I no longer believe any of them present any meaningful data worth wasting time considering.

Lighting is Always Human Centered – Duh

All lighting design is, by definition, centered on its impact on human visual perception and performance. We do not design lighting for our pets, nor doe we light spaces for some alien entity. Therefore, all lighting design is human-centric, making the term itself nothing more than a statement of the obvious. The IES, and its members, have published literally millions of pages on the topic of applied lighting design to enhance human performance, comfort and health under artificial light. Surrounding this considerable effort is a massive amount of research into the qualities of a lighting systems from light sources to application strategies.  However, little of this has focused on LED technology and its unique characteristics in application of research findings to practical application. A great deal of research does not include any specific light source at all, so may or may not apply to LED application. Most legitimate studies either remove the effect of any light source, or state the specific source utilized in the work. Transferring conclusions between these and to LEDs that were not included in the work itself, requires a very careful scientific process that takes into consideration potential misrepresentations.

Anyone that truly wants to understand all of this and its relationship to human phototransduction should spend a great deal of time reading the numerous studies and papers offered by the LRC on this topic.  The LRC also offers up a Circadian Stimulus Calculator  as well as research findings published in LD&A on the topic.

LED Advantage Claims

Assertions that LED technology produces a specifically unique capacity to deliver healthful effects, particularly for imposing control of circadian cycles and/or melatonin levels, are founded on simplistic interpretations of cherry picked information from broader studies that did not use LED light sources during investigations. LED spectral power and the response curve of the newly discovered ipRGC and pRGC’s are roughly aligned, for some LED sources, but not all. Photo-receptor peak response between 460nm and 480nm, is roughly aligned with a typical 456nm blue pump white light source, but enough different as to reduce its efficacy. 405nm violet pump white light sources deliver an even lower efficacy in delivering the desired SPD. The peak at 456nm exists regardless of light source phosphor generated CCT color, so there is very little real difference between a 3000K, 4000K and 5000K light source. This puts the concept of white light tuning, based on balancing white light sources in question. True tunable light sources, designed to produce human non-visual entrainment, or phase response  requires the inclusion of a blue light source, ideally with a peak of 480nm, to enhance the core white light source output to produce the spectral power differential and efficacy necessary to produce the desired effect.

There have been proven instances where a 3000K light source generates a higher melatonin suppression response than a 5000K LED source. The reason for this is simple. CCT is not the indicator of suitability, or activation of human non-visual response – Spectral Power Distribution is. For this reason, virtually all products marketed using “tuning” of white light sources as their core technology, under the simplistic concept that CCT tuning as an effective strategy – are likely to be ineffective. If there is no SPD data provided to support claims made, the claims are likely unqualified. Further, CCT with not consideration of illuminance levels, are ignoring the science behind the technology. At a very minimum, most simple interpretations of the science involved with human entrainment, there is a need to adjust both SPD content and illuminance levels by between 50% and 75%. In many studies, illuminance levels alone, with no change in SPD are cited with no mention of SPD tuning at all, indicating that CCT tuning is not a necessary factor. LD&A has an interesting article on the topic, showing the approach of illuminance levels and combined CCT/SPD content effects. This article clearly describes the need to consider SPD of the light sources, outlines the need for increased retinal illuminance, and explains that the application of light for Circadian Stimulation is most effective in early parts of the day.

Putting these Simplistic Notions Aside for a Moment

There are numerous studies showing that light therapy can be effective in resetting the Circadian cycle each day, through early morning application for a prescribed period of time, at a specific elevated illuminance level, with a light source containing specific SPD content. Thus has been applied in chemo therapy patients, Alzheimer suffers, shift workers, and in lab settings.   However, there is very little work that conclusively supports the case for applying CS light at other times of the day. In other words, the idea of applying light to dope the SPD to create an energizing effect “on demand” throughout the day is not based on research results, it is essentially conjecture. In the LD&A article, as it is with numerous other clinical studies, there is evidence that the circadian cycle is over a 24+/- hour period of time, not moment-by-moment.

The mechanism of serum melatonin levels in the blood and exposure to light has been well documented. There is also evidence that light suppression of melatonin may be linked to cancer and type 2 Diabetes. There is also evidence that manipulation of melatonin levels, through application of light, may induce sleep disorders that actually worsen human health and well-being. The article published on the NCB web site – Light, Melatonin and the Sleep-Wake Cycle describes effects of improper melatonin levels imposed by drugs and light. The question of low serotonin levels  caused by too little light mid-day are widely discussed – primarily driven by marketers of light therapy boxes.

There is consensus, in the scientific community directly involved in the study of light and human physiological response, that there are numerous mechanisms involved in the synchronicity of human circadian responses that are not fully understood, thus it is currently impossible to point to any one factor as a key trigger, including light.

The CIE has issued a document clearly stating this, titled “Statement on Non-Visual Effects of Light” Further to this, the CIE has published the results of its investigation on the topic under TN-003, outlining current thinking on the topic, identifying gaps in knowledge requiring further study. While there are statements recognizing that light effects numerous non-visual responses, including hormonal, circadian, and melatonin, they further establish that there are no recommendations to adapting this knowledge. Further, attributions of NASA having established recommendations are premature. NASA is in the process of studying the effect of light, specifically LED light, and its effect on human circadian response and sleep cycles, under “Testing Solid State Lighting Countermeasures…” the research and experimentation is in process and incomplete. There are no conclusions, nor are details of the drivers in the desired effects established. Drawing any conclusion simply on the basis of NASA doing experiments is premature. Any speculation as to what they will find, is purely speculation. Boeing is also cited regularly, in its deployment of LED lighting technology and human-centric lighting. However, this information is generally founded on marketing the Dreamliner and its special lighting effects, and theories forwarded as marketing statements. Lumileds forwards similar claims, with no citing of scientific backing for claims, in its promotion of LED technology use by Airbus.

While it is widely recognized that light has an impact on sleep cycles -this is hardly revolutionary, nor is it even insightful. Of course light has an impact on sleep cycles. This is why shift workers cover windows to allow them to sleep during daylight hours. It has also been recognized that short daylight cycles experienced in the winter, combined with reduced intensity, are contributory to Seasonal Affect Disorder. However, even here, specific recommendations regarding light, light sources, light qualities, are limited, and overly generalized, as research on this topic is incomplete and frequently contradictory. Many studies have found exercise has a similar affect to photo therapy, indicating, as the CIE has noted, there is a great deal more than needs to be understood, before recommendations can be developed. There are also studies investigating the use of light therapy to re-set disrupted circadian cycles, such as “Therapeutics for Circadian Rhythm Sleep Disorders“. However, these studies frequently include treatments that include light in addition to other treatments, such as Vitamin B12, or exercise routines.

The real question is: How much do sleep studies apply to waking hour work life activity. Even if it is proven that a specific photo therapy program will re-set a circadian cycle, it is an extreme stretch to apply this to artificial lighting systems, unless we know specifically what the long term effect are, and whether continuous exposure under general illumination has the same affect as short-term therapeutic treatments carried out in supervised studies. None of this is known at this time, nor is it expected to be fully understood in the near future. Their are also questions of conditioning, where any lighting effect repeated daily becomes less effective over time.

Based on this, one thing can be concluded: Marketing behind tune-able white LED products, specifically espousing its benefits of increasing attention and engaging students, or occupants, is not founded on scientific recommendations or protocols that have considered the overall effect, sustainability and safety of such application. We do know, however, that humans have worked under a great many lighting conditions that are well-recognized to be less than ideal, and survived with minimal known and defined long-term effect. In this, application of tuned white light, at its very best, will likely do no harm – even if proven to be completely ineffective in delivering on its promise to improve health and feeling of well-being. Until the combination of SPD, illuminance level (at the retina), exposure time, and numerous other physiological conditions that are involved beyond light, is fully defined and understood, any assertions that light alone as a solution is a false claim. This is particularly true of CCT tuned sources, which may actually act in the reverse of claims, if the light sources utilized are not carefully selected.

Recently, one specific large-scale manufacturer (name withheld) has released its tune-able white program espousing several claims that are not only pseudo science, but simply incorrect when put under the light of real science on the topic. Here are the specific claims they are making in context to a classroom environment:

  1. A warm white 3000K light setting provides a soothing environment for children to read under.
  2. A “neutral” white of 3500K for testing
  3. A 4200K light for “collaboration” and general uses
  4. A 5000K light for energy and recovery of mid-afternoon drowsiness

These recommendations are nonsense, and are not supported by any actual scientific evidence or support. Many of these recommendations are not just wrong, they are counter to known science. For example, the recommendation for warm light for reading and testing is known to reduce visual acuity, accuracy and reading speed. These recommendations are essentially based on intuitive “feel good” romanticism. This is also an irresponsible application of a technology, and the type of marketing that destroys credibility.

New Expertise Required – Perhaps a New Discipline in Design

In my opinion, the application of any environmental factor that is directly intended to impact or affect human occupants, requires very careful consideration and expertise well beyond that of manufacturers and marketers. It is irresponsible to apply any technology intent to change behavior without first insuring it is safe, is controlled, and monitored. Further, the design of such systems must include application of all known science and understanding, expertly formulated to produce the effects claimed. This, again, is outside the purview of marketers. Few lighting design professionals are currently equipped to apply this technology. Until there are standards developed to identify the factors involved, all applied products, and assertions are nothing more than marketing efforts, with no more validity than any other preceding crack-pot science being presented to the lighting market today. There is a strong chance that a new design discipline, with specific medical educational requirements, may need to be created and applied, to bring this technology to fruition – eliminating the off-the-cuff anecdotal and subjective application to an end, in order to avoid potential harmful unintended effects to human health.

Bottom Line

Here is what is known, from actual research on the topic:

  1. Human-Centric is a term created by those marketing the concept of applying light to deliberately effect human physiological response to light.
  2. White light CCT tuning is not “Human-Centric Lighting”. White light tuning is a form of decorative lighting effect, like colored lighting, and nothing more.
  3. It is not the CCT of a source that creates effects on human non-visual response to light, it is the specific Spectral Power Distribution, which may or may not correlate with an actual CCT value. Further, the SPD of a light source is not the only factor in its effectiveness in creating a CS response.
  4. Illuminance levels are an integral consideration, and may be the most critical component, in realizing a positive, intentional circadian response – regardless of SPD content approach or tuning effect.
  5. Numerous studies have shown that light sources with high S/P ratios (Scotpic/Photopic) deliver the highest visual performance (See IES TM-24), which includes reading acuity and accuracy. This has a rough correlation with high CCT sources, but only in as much as this represents the SPD content of sources available for purchase. It is entirely possible to produce a lower CCT product with the SPD required to generate a high S/P ratio. S/P ratios have a significant effect on illuminance perception, thus are a component of attaining optimization of human response, thus are as much a part of the approach to enhancing lighting’s impact on human health, comfort and performance.
  6. The research on the topic of human circadian response to lighting and other involved factors, is incomplete, with preliminary data indicating lighting alone may not be the strongest or most important factor.
  7. There is zero research indicating that manipulating circadian response through lighting throughout daytime activities improves human health, well-being or even comfort, while there is some evidence that manipulation of melatonin levels may have negative health effects.
  8. To repeat: All claims of human-centric lighting based solely on white light tuning founded only on CCT manipulation, are nothing but marketing, with virtually no indication that the desired effect will ever be realized – no matter how compelling the marketing literature and citing of anecdotal statements might be.
  9. Until the application of light to manipulate circadian cycles, melatonin levels, and the mechanisms related to both as they relate to human health are fully understood, application of any method to rush this into the market is irresponsible. The risks of inducing cancer, type 2 diabetes, or other potential diseases must be understood before this technology is applied. Further, the occupants of space exposed to this technology must be informed.
  10. Ultimately, the application of light and related factors, to better human health and feeling of well-being in lighted spaces, will require specialist knowledge, expert application of scientifically founded technologies, with consideration of the behavior of occupants being affected. Anything short of this is irresponsible.

I suggest that prior to applying any lighting under the guise of “Human-Centric” with the promise to improve human health, safety, and well-being, that a cautious approach placing scientific understanding in front of marketing claims, is beyond prudent – it is the only responsible approach. For any widespread application, such as schools, or health care facilities, the need for careful application, by qualified designers using products that are confirmed to produce the necessary SPD content, is necessary. Poorly considered and misapplication of this technology is not only a waste of time, it has the potential of producing an undesirable effect. Finally, it must be considered that manipulating light to change human response or behavior, is a deliberate act that is analogous to manipulating air quality by introducing gases that cause occupants to feel more energetic, or doping water systems with stimulants to improve attention and productivity. This requires far more consideration than simply buying into the latest populist marketing claims, and has the potential for future unforeseen legal ramifications, should the application be discovered to have negative effects not yet revealed or fully understood. We cannot risk introducing a lighting technology into the market that one day becomes the target for class level legal action. When the technology is fully understood, and standards created, as well as procedures to ensure that risks are being controlled with the same vigor as the desired effects, it may indeed be a revolution in lighting. It may also prove to be dangerous in the hands of amateurs and marketers, who push it into the market without legitimate qualification.

The counter argument to all of this is that the light we are exposed to on a daily basis has not be fully vetted as to its effect on human physiological response, and that there are known negative effects of current lighting systems not being addressed, thus, any deliberate manipulation under the heading of “Human-Centric” is no worse, and potentially an improvement. This is patently fallacious. Ignorance or institutional acceptance of the effects of current lighting practice is not justification to move forward with another, equally flawed and ignorant lighting practice. Pandora’s box has been opened, and broadcast to the universe by those marketing the concept of deliberately manipulating light to cause human physiological response – with the further statement that existing lighting practice has negative effects now known and in need of redress. This means that the clock is now ticking down to the moment when lighting professionals, marketers and manufacturers may face liability for failing to resolve and address a recognized health risk.

Another design professional that has addressed this issue, Deborah Burnett, summarized her thoughts on this at LEDs magazine in her article “First do no harm”  This is solid reading, with a similar conclusion, for anyone considering this technology in their design work.


Here is an article from LUX magazine that I believe nails this topic well:

Another from this same publication also adds insight into the effect of light on setting the circadian clock with a video interviewing Russell Foster – who is a pioneer on this topic:

More from Russell Foster – which contends the topic requires more research, and that it is not all about blue-good, red-bad over-simplification:

Update: Comments have been closed on this article. If you would like to discuss this article, offer constructive criticism, point to additional research of interest to others on this topic, please contact me directly, and I will revise the article accordingly. This is an interesting and developing subject and technology that will keep us all interested for years to come. Let’s keep it friendly and civil, shall we?