Andreas Wojtysiak ist promovierter Biologe und nach Tätigkeiten am IMST in Kamp-Lintfort, in der Medizinischen Fakultät der privaten Universität Witten/Herdecke und bei BenQ Mobile in München seit 2008 bei der Osram AG München als Innovation Manager Light & Health beim Strategic Innovation Management (SIM) aktiv.

Alfred Wacker (Dipl.-Ing.) war früher Leiter des Marketings bei OSRAM und ist nun für seine Firma beratend und in internationalen Gremien und Komitees tätig, u. A. im "Lighting Technology Standards Committee NA 058-00-27 AA (FNL 27) 'Effects of light on human beings' at DIN", dem auch die Schweiz angehört.

Dieter Lang (Dipl.-Phys.) forschte früher bei Osram an "ceramic metal halide lamps" und ist seit der Formierung des Corporate Innovation Management Department im Jahr 2004 als Head Europe zuständig für Innovationen.

Lighting Application for Non-Visual Effects of Light

Andreas Wojtysiak, Alfred Wacker and Dieter Lang, Osram AG

 

Introduction

The discovery of melanopsin containing retinal ganglion cells with intrinsic photoreception (ipRGC) at the beginning of this millennium [1, 2, 3] evoked interest not only in the research community, but also in the lighting industry. Beneficial health effects of light have been discussed not only since evidence for the use of light in psychiatric disorder therapy was achieved. One obvious drawback for broader application was always the need for additional energy, because clear effects with the typical light used for illumination purposes were dependent on higher illumination levels. It now has turned out, that the lighting used in previous laboratory and application studies was not sufficiently adapted to the non-visual reception system and cofactors could have masked these effects considerably. Though there is still discussion about the optimal lighting for non-visual effects with minimum energy use, there is no doubt in the scientific community that appropriately timed stimulation of the ipRGC during the day and avoidance of stimulation in the night stabilizes our circadian system. This leads to a more efficient nocturnal sleep and better daytime activity and alertness levels. Alertness is also directly affected by input to the ipRGCs, resulting in acutely increased performance in laboratory testing and higher activity levels in corresponding nuclei of the brain [4]. This article will highlight how to transfer scientific results on non-visual effects - also called biological effects - of light into lighting application.

 

Fig. 1: action spectrum c(λ) for biological effects and visual sensitivity curve v(λ) combined from different sources.

Lighting Technology for non-visual effects

Light Sources

A number of studies on the ipRGC have shown that the action spectrum of their photopigment melanopsin peaks in the blue spectrum around 480 nm. No nervous cell responses were elicited by yellow or red light. The best described action spectrum for a more complex biological response is the curve for nocturnal melatonin suppression. Several models have been developed to describe this response with minor deviations when these were used to rate white light with respect to its circadian input. The models of Gall [5] and Rea [6] differ with respect to the effect of light in the green wavelength region, which might be of interest when comparing small waveband (colored) light sources. In total, it can clearly be stated, that blue spectral components in light act on the internal clock system by affecting circadian amplitude and phase.

The model from Gall [5] was implemented in the German prestandard DIN V 5031-100:2009 [7], which contains terms and definitions for biological effects of light. Using the metrics described there, it is possible to rate lamp spectra according to their biological efficiency in addition to light output for vision. A lamp spectrum with a higher so-called biological action factor (abiol v ≥ 0,8) has a high fraction of short wavelength spectrum, a high correlated color temperature, and is generally more suitable to represent the active and day time part of the circadian day, especially in the morning hours. Cool white light sources including LEDs and fluorescent lamps may be used for this purpose. While stabilizing circadian rhythms when applied over the day, this spectrum is not suited for the regenerative and nocturnal phases, typically in the late evening and night. Warm white lamps with low biological action factors (abiol v ≤ 0,4) have a lower influence on the ipRGCs and on the internal clock. These lamps are more suited when light for vision is needed, but an influence on the circadian phase or an alerting effect should be avoided. Halogen lamps, warm white LEDs or fluorescent lamps are suited to achieve this.

To balance best with visual and ecological needs, it seems advisable to use different CCT lamps or light sources with high energy efficiency over the day and use them as needed. This will result in higher installation costs in the short term, but will be the most sustainable solution in the long run.

Luminaires

The biological photoreceptors are widely distributed over the eye’s retina and more sensitive in the nasal and inferior region than in the upper part [8]. For biological effects it is essential to address many of these receptors, like the sky does in nature. Good effects indoors will be achieved with light coming from the upper field of view and covering a wide solid angle, e. g. from the ceiling and the upper surfaces of walls. Consequently, biologically effective illumination requires planning and luminaires fitting to this concept, with a high proportion of indirect lighting or laminar design, thus leading to suitable vertical illumination levels. Up to now, no dose-response curve describing the relationship between lighting area and biological effect size has been established. In the meanwhile, the general recommendation for application must be to "maximize" the lighting area, while keeping luminance levels low in order to avoid glare effects.

Controls and Light Management Systems (LMS)

Natural daylight is highly variable, especially in terms of illuminance levels but also in terms of color temperature. It is clear that the dynamics of daylight follows a rhythmic change in the course of day and night, and that this is a benchmark for good artificial lighting also. For day time application, changes in biological efficiency of applied lighting with positive impact on circadian rhythm stability, sleep/wake cycle, alertness and cognitive performance can be achieved with light management technology already available. The biological effectiveness in nature emanates from a combination of spectral composition and illuminance level, being in average at highest level around noon and at minimum in the night. Technically, this situation can be simulated by dimming the relative contribution of lamps with different light colors against each other in order to have a white light color but with different portions of blue spectral components appropriate to the respective daytime.

Warm colors with only little biological effects can maintain good vision without strongly influencing circadian effects in the evening, while cooler colors with enriched blue content used over the day are providing good vision and higher biological effectiveness simultaneously. The evening and night scenario also allows to reduce the laminar light distribution and a change to spot-like illumination exclusively. This allows also substantial reductions in amount of energy needed for lighting, as only the visual tasks and emotional aspects have to be respected in these hours. Reductions in energy consumption may further be achieved by including sensors and intelligent controls, without deductions in illumination quality.

Lighting Application Studies

Application studies (like the examples below) showed, that non-visual effects of light may be achieved with moderate effort in energy consumption by using modern lighting systems and control. The general strategy is to differentiate lighting according to time of the day and needs.

Better lighting in nursing homes improved the nocturnal sleep and daytime activity as well as psychological scores of elderly persons in several studies [9, 10]. Old persons are especially dependent on a lighting change because of their reduced transmission of the dioptric apparatus. The hazing and yellowing of the lenses with age reduces drastically the short wavelength light arriving at the retina. This effect was counteracted by the lighting.

A stronger synchronization by daytime office light and improvements in subjective performance in office workers have been achieved with fluorescent lamps of higher CCT than the typical 4000 K lamps used in this application [11, 12]. For daytime indoor workers, this could be a first step to a better lighting but it is needed to say that this scenario might not be optimal for late office hours.

Comparable benefits have been shown in schools, leading to increased scholar performance of the pupils and in hospital settings, where the recovery phase could be shortened.

Conclusion

Although scientific researchers still have numerous questions in this field, these first results of application of the new findings on non-visual effects of light open a very promising future for improvements in interior illumination. This is true for the professional lighting as well as for the lighting at home.

Fig. 2: Lighting concept with pendant luminaires for day-time office workers including non-visual effects of light:
Left: Day scenario with task lighting by warm white direct light and additional cool white light to the ceiling and upper wall to address ipRGC.
Right: Evening and night scenario with warm white task lighting only.

 

References

[1] Brainard, G. C., et al. (2001). "Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor." J Neurosci 21(16): 6405-12.
[2] Thapan, K., et al. (2001). "An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans." J Physiol 535 (Pt 1): 261-7.
[3] Berson, D. M., et al. (2002). "Phototransduction by retinal ganglion cells that set the circadian clock." Science 295(5557):1070-3.
[4] Vandewalle, G., P. Maquet, et al. (2009). "Light as a modulator of cognitive brain function." Trends Cogn Sci 13(10): 429-38.
[5] Gall, D., Bieske, K. (2004). Definition and measurement of circadian radiometric quantities. CIE Symposium '04: Light and Health: non-visual effects, University of Performing Arts, Vienna, CIE.
[6] Rea, M. S., et al. (2005). "A model of photo¬transduction by the human circadian system." Brain Res Brain Res Rev 50(2): 213-28.
[7] DIN V 5031-100:2009-06 Optical radiation physics and illuminating engineering - Part 100: Non-visual effects of ocular light on human beings - Quantities, symbols and action spectra
[8] Glickman, G., et al. (2003). "Inferior retinal light exposure is more effective than superior retinal exposure in suppressing melatonin in humans." J Biol Rhythms 18(1):71-9.
[9] Van Someren, E. J., A. Kessler, et al. (1997). "Indirect bright light improves circadian rest-activity rhythm disturbances in demented patients." Biol Psychiatry 41(9): 955-63.
[10] Riemersma-van der Lek, R. F., D. F. Swaab, et al. (2008). "Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial." JAMA 299(22): 2642-55.
[11] Vetter, C., M. Juda et al. (2011) “Blue-enriched office light competes with natural light as a zeitgeber”; Scand J Work Environ Health 37(5): 437-445
[12] Viola, A. U., L. M. James, et al. (2008). "Blue-enriched white light in the workplace improves self-reported alertness, performance and sleep quality." Scand J Work Environ Health 34(4): 297-306.

 

 

Jet Lag and Shift Work

Natural light sets the internal clock, but humans often challenge this system with more or less voluntary changes in day/night behavior. Jet travel is such a challenge, shift work is another. The internal clock shifts about 1 hr per day in such scenarios. With timed biologically active light (as described in the main text) and avoidance of light at other appropriate times, it appears possible to adapt to a new time zone much faster. Shifts of more than 3 hrs with one light episode have been achieved in laboratory settings [a]. But at present, there is no reliable and robust scientific base how to handle lighting for shift workers. Actual recommendations range from shortening the shift schedules in order to reduce frequent massive circadian disruption as stated by some ergonomics experts to shifting totally (also in the worker’s free times) to the new shift schedule as proposed by chronobiologists, with considerable consequences for social life of those affected [b].

[a] Khalsa, S. B., M. E. Jewett, et al. (2003). "A phase response curve to single bright light pulses in human subjects." J Physiol 549 (Pt 3): 945-52.
[b] Roenneberg, T. (2009): "New approaches in investigating the consequences of shift-work". 3rd DIN Expert Panel Effect of Light on Human Beings, DIN. Berlin, Beuth Verlag.

 

[Released: May 2012]