Light and circadian effects Janos Schanda 1and Agnes N. Vidovszky 2 1 University of Pannonia 2 Technical University of Budapest

Overview Introduction Introduction The intrinsically photosensitive Retinal Ganglion Cells (ipRGC) and their effect The intrinsically photosensitive Retinal Ganglion Cells (ipRGC) and their effect Melatonin supression and possible side effects Melatonin supression and possible side effects Lighting and the circadian effect Lighting and the circadian effect Conclusions and summary Conclusions and summary

Circadian rhythm - chronobiology

Neuroanatomy of light From: Brainard GC, Glickman G (2003) The biological potency of light in humans: significance to health and behaviour. CIE 152:2003. pp. I-22 – I-33.

Chronobiology effects Influencing the circadian rhythm Influencing the circadian rhythm Jet-lag Jet-lag Shift-work Shift-work Sleeping disorder Sleeping disorder Seasonal affected disorder (SAD) Seasonal affected disorder (SAD)

Early findings 1000 lx min exposure: 1000 lx min exposure: Decreases melatonin secretion Decreases melatonin secretion Increases cortisol secretion Increases cortisol secretion Increases pulse rate Increases pulse rate Increases body temperature Increases body temperature Decreases pupil diameter Decreases pupil diameter Increases alertness Increases alertness Has an effect to decrease SAD syndrome Has an effect to decrease SAD syndrome

Action spectrum of melatonin suppression Some retinal ganglion cells contain melatonin, with a short wavelength visible light absorption spectrum Some retinal ganglion cells contain melatonin, with a short wavelength visible light absorption spectrum their excitation influences melatonin secreation into the blood. their excitation influences melatonin secreation into the blood. Possible regeneration mechanism and spectral sensitivity still not cleard Possible regeneration mechanism and spectral sensitivity still not cleard

Alternative circadian action spectrum Rea-Fiuerio-Bierman-Bullough: Circadian light, J. Circ.Rhythms Rea-Fiuerio-Bierman-Bullough: Circadian light, J. Circ.Rhythms Simultaneous broad-band stimulation and pre- stimulation have different effects, still not cleared completly

Early suggestions, 1 Light source with K correlated colour temperature Light source with K correlated colour temperature

Early suggestions, 2 Change the illumination and CCT during the day in work-places to keep alertness Change the illumination and CCT during the day in work-places to keep alertness Negaive effects: possible cancer risk Negaive effects: possible cancer risk

Possible influence, night time, outdoor Rea-Smith-Bierman-Figueiro: The potential of outdoor lighting for stimulating the human circadian systemASSIST 2010

Effect of circ.stimulating radiation on humans of different age Piazena-Kockott-Uebelhack. Lux Europa 2005.

Questions Should the Should the intensity intensity evenness evenness correlated colour temperature (CCT) correlated colour temperature (CCT) of artificial light be made variable, so that it looks more similar to daylight? of artificial light be made variable, so that it looks more similar to daylight? Has it negative effects if tiredness is suppressed by changing the spectrum of white light? Has it negative effects if tiredness is suppressed by changing the spectrum of white light? What is the preferred LED spectrum What is the preferred LED spectrum

Harmonic relationship between CCT and illuminance

LEDs used in the present investigation

Calculations, starting assumptions We tried to keep the CCT of the LEDs near to 2860 K We tried to keep the CCT of the LEDs near to 2860 K Intention: use in interior spaces, thus R a >50 required Intention: use in interior spaces, thus R a >50 required To requirements To requirements For morning scenes: big C/  ratio For morning scenes: big C/  ratio For evening relaxation (permit melatonin secretion) small C/  ratio For evening relaxation (permit melatonin secretion) small C/  ratio

19 real LED spectra have been used 2860 K correlated colour temperature was set to optimize the spectra for C/ , using the circadian action spectrum defined by Gall 2860 K correlated colour temperature was set to optimize the spectra for C/ , using the circadian action spectrum defined by Gall

Computation Determine LED chromaticity using CIE colour Matching Functions (CMF) Determine LED chromaticity using CIE colour Matching Functions (CMF) Determine RGB-LED combination spectrum with Excel Solver routine; minimize chromaticity difference Determine RGB-LED combination spectrum with Excel Solver routine; minimize chromaticity difference

Results: change of Ra Keeping the blue LED spectrum constant, peak wavelengths of the red and green LEDs for equal TCC, change of R a. Keeping the blue LED spectrum constant, peak wavelengths of the red and green LEDs for equal TCC, change of R a.

Circadian effectiveness depends on blue LED spectrum: C/  of LED combinations For all Red and Green LEDs the curves are the same For all Red and Green LEDs the curves are the same Peak wavelength of Blue LED influences C/  Peak wavelength of Blue LED influences C/ 

Conclusions 1 RGB-LEDs using a 470 nm blue LED can have circadian effectiveness similar to incandescent light RGB-LEDs using a 470 nm blue LED can have circadian effectiveness similar to incandescent light By decreasing the wavelength of the blue LED, the melatonin suppression effectiveness decreases, and the colour rendering decreases too By decreasing the wavelength of the blue LED, the melatonin suppression effectiveness decreases, and the colour rendering decreases too By increasing the wavelength of the blue LED, the melatonin suppression effectiveness increases, but the colour rendering decreases By increasing the wavelength of the blue LED, the melatonin suppression effectiveness increases, but the colour rendering decreases

Conclusions nm blue, 556 nm green and 622 nm red LED combination provides better evening light than incandescent lamp 470 nm blue, 556 nm green and 622 nm red LED combination provides better evening light than incandescent lamp 490 nm blue, 556 nm green and 622 nm red LED combination provides better morning light than incandescent lamp, but R a decreases to the minimum permited value 490 nm blue, 556 nm green and 622 nm red LED combination provides better morning light than incandescent lamp, but R a decreases to the minimum permited value Follow up investigations will be conducted with 4 or 5 LED combinations to increase R a Follow up investigations will be conducted with 4 or 5 LED combinations to increase R a Non-additivity has to be studied Non-additivity has to be studied

Conclusions 3 One can influence the circadian effect even at low correlated colour temperatures, it is not necessary to use light of extremely high colour temperature One can influence the circadian effect even at low correlated colour temperatures, it is not necessary to use light of extremely high colour temperature Before trying to influence the circadian rhythm with lighting the possible consequences, mainly cancer risk, has to investigated. Before trying to influence the circadian rhythm with lighting the possible consequences, mainly cancer risk, has to investigated.

Use light carefully Amber LED light of 10 lx can enable seeing at night in the bathroom without influencing the circadian rhythm Amber LED light of 10 lx can enable seeing at night in the bathroom without influencing the circadian rhythm Figueiro LD+A 2005

Final suggestion The large screen high brightness modern TV can have an influence on the circadian rhythm: do not use it in your bedroom The large screen high brightness modern TV can have an influence on the circadian rhythm: do not use it in your bedroom

Thanks for your kind attention! This publication has been supported by the TÁMOP-4.2.2/B-10/ project.