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Light and circadian effects

Light and circadian effects. J a nos Schanda 1 and Agnes N. Vidovszky 2 1 University of Pannonia 2 Technical University of Budapest. Overview. Introduction The intrinsically photosensitive Retinal Ganglion Cells (ipRGC) and their effect Melatonin supression and possible side effects

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Light and circadian effects

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  1. Light and circadian effects JanosSchanda1 and Agnes N. Vidovszky2 1 University of Pannonia 2 Technical University of Budapest

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

  3. Circadian rhythm - chronobiology

  4. 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.

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

  6. Early findings • 1000 lx 20-30 min exposure: • Decreases melatonin secretion • Increases cortisol secretion • Increases pulse rate • Increases body temperature • Decreases pupil diameter • Increases alertness • Has an effect to decrease SAD syndrome

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

  8. Alternative circadian action spectrum • Rea-Fiuerio-Bierman-Bullough: Circadian light, J. Circ.Rhythms 8 2010. Simultaneous broad-band stimulation and pre-stimulation have different effects, still not cleared completly

  9. Early suggestions, 1 • Light source with 17.000 K correlated colour temperature

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

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

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

  13. Questions Should the intensity evenness correlated colour temperature (CCT) 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? What is the preferred LED spectrum

  14. Harmonic relationship between CCT and illuminance http://www.lamptech.co.uk/Images/Illustrations/FL%20Kruithof%20Diagram.jpg

  15. LEDs used in the present investigation

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

  17. 19 real LED spectra have been used 2860 K correlated colour temperature was setto optimize the spectra for C/F , using the circadian action spectrum defined by Gall

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

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

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

  21. Conclusions 1 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 melatoninsuppression effectiveness decreases, and the colour rendering decreases too By increasing the wavelength of the blue LED, the melatoninsuppression effectiveness increases, but the colour rendering decreases

  22. Conclusions 2 470 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 Ra decreases to the minimum permited value Follow up investigations will be conducted with 4 or 5 LED combinations to increase Ra Non-additivity has to be studied

  23. 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 Before trying to influence the circadian rhythm with lighting the possible consequences, mainly cancer risk, has to investigated.

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

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

  26. Thanks for your kind attention! This publication has been supported by the TÁMOP-4.2.2/B-10/1-2010-0025 project.

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