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Cajochen, Phd Centre for Chronobiology Psychiatric Hospital of the University of Basel, Switzerland Beyond our eyes: the non-visual impact of light Christian Cajochen, PhD Centre for Chronobiology Psychiatric Hospital of the University of Basel, Switzerland Workshop Intelligent Efficient Human Centric Lighting Muttenz/Basel 12.. December 2016 Thomas Edison was maybe wrong ! Light is the most important Zeitgeber ! Buttgereit, Smolen, Coogan, Cajochen, Nat Rev Rheumatol, 2015 Light and human circadian rhythms Melatonin as the best circadian marker in humans Induction of a Phase Delay in the Human Circadian Melatonin Rhythm by Light (10’000 lux for 6.5 h) Midpoint Midpoint 4:45 8:21 400 Light /L) 300 pMol 200 100 Plasma Melatonin ( Melatonin Plasma 0 12 24 12 24 12 24 12 24 12 Time of Day Sleep period Khalsa et al., J Physiol (London) 2003 Light and circadian phase Phase-Response Curve 4 3 2 (h) 1 shift 0 -1 Phase -2 -3 6.7 hours 10’000 lux -4 polychromatic whiteRetina light -18 -15 -12 -9 -6 -3 0 3 6 9 12 15 18 Initial Phase (time relative to DLMO=0) Khalsa, et al., J Physiol (London) 2003 «Light impacts on our circadian rhythms more powerfully than any drug» Charles Czeisler «Casting light on sleep deficiency» Nature, 2013 Suppression of melatonin in a totally blind person with bright light Sighted Person 300 200 Plasma Melatonin 100 (pmol/liter) 37.5 37.0 Core Body Temperature 36.5 (°C) 36.0 12 18 24 6 12 18 24 6 12 Time of Day (h) Blind Person 300 200 Plasma Melatonin 100 (pmol/liter) 37.5 37.0 Core Body Temperature (°C) 36.5 36.0 12 18 24 6 12 18 24 6 12 Time of Day (h) Czeisler et al., New Engl Med 1995 Light is more than vision non-visual / non-image forming light effects Light can be «seen» without conscious vision «Forced choice» test in a totally blind person 100 * 80 60 40 Correct Answer (%) Answer Correct 20 0 420 460 481 500 506 515 540 560 580 Wavelength (nm) Nach Zaidi et al., Curr Biol, 2007 Non-classical Photoreceptor intrinsic photosensitive retinal ganglion SCN cells (iPRGs, Melanopsin) (circadian Pacemaker) Eye A dual sensory organ Rods Retina Cones Hattar et al. Science, 2002 Berson et al. Science, 2002 Light and circadian phase Phase-Response Curve 4 3 2 (h) 1 shift 0 -1 Phase 75 % of the resetting -2 response -3 6.7 hours 10’000 lux -4 polychromatic whiteRetina light 6.5 hours blue light (480 nm) -18 -15 -12 -9 -6 -3 0 3 6 9 12 15 18 11.8 μWcm−2, 11.2 lux) Initial Phase (time relative to DLMO=0) Khalsa, et al., J Physiol (London) 2003 Rüger, et al., J Physiol (London) 2013 Why is this relevant: Light bulb versus LED Relative Contribution Relative Wavelength (nm) Relative Contribution Relative Wavelength (nm) Smartphone use in adolescents (14-20 years) Use of smartphones Where do you keep your smartphone during night? 1 hour prior bedtime irgendwo in der Wohnung 14% 23% irgendwo im Zimmer 99 % Ja auf dem Nachttisch nicht beantwortet im Bett 60% 99% yes nicht beantwortet 97% in bedroom How often do you use your smartphone after «Lights off» 10% nie 15% selten 49% gelegentlich häufig 25% nicht beantwortet Strube et al. Somnologie, 2016 74% occasionally-often Light has also «non-circadian» acute effects • Light suppresses the soporific hormone melatonin within minutes (Gronfier et al., 2002) • Light inhibits sleep-promoting GABA neurons in the ventrolateral preoptic area in the hypothalamus (VLPO, Tsai et al., 2009) • Light activates wake-promoting orexin neurons in the lateral hypothalamus (McGregor et al., 2011) Acute sleep induction by light in nocturnal mice Lights ON Lights OFF 60 Wildtype Melanopsin knockout Melanopsin aDTA 30 Response (min) Response Sleep 0 0 1 2 3 Time elapsed from light onset (h) According to Muindi et al., Front Syst Neurosci, 2014 Acute alerting effects of light in diurnal humans Subjective Alertness 5 10 more alert more 15 20 120 lux ! 25 10 100 1000 10000 Illuminance (lux) Cajochen et al., Beh Brain Res. 2000 The human alerting response to light is blue-shifted Monochromatic light Energy Saving Lamps Computer Screens 50 8 6 40 30 7 light - 5 20 0 = 0 pre Sleepiness Scale (KSS) Scale Sleepiness Sleepiness Scale (KSS) Scale Sleepiness % Sleepiness Change Sleepiness % 10 6 Karolinska Karolinska 0 4 Cajochen et al., Sleepiness and human impact assessment Book chapter, Springer, 2014 Sustained Attention and Response Control (Go/noGo Task) Letter „W“: go Letter „M“ : no-go 90 faster 95 LED Screen Baseline 100 Dark Adaptation 105 Relative Reaction Time (%) Time Reaction Relative * Non-LED* Screen slower 110 * P <0.05 18:15 19:15 20:15 21:15 22:15 23:15 00:15 Monitor: F1,11=12.2; p<0.04 Time of day: F11,44=7.8; p<0.02 Time of Day (h) Monitor x Time: F12,132=3.0; p=0.041 Cajochen et al., J Appl Physiol. 2011 Declarative Learning (Word pairs) Correctly identified old word pairs Correctly identified new word pairs 70 70 * 65 65 60 60 % 55 55 50 50 45 45 LED Screen * P <0.05 Non-LED Cajochen et al., J Appl Physiol. 2011 Light is not just for vision Cortex Thalamus Hypothalamus Brainstem - Locus coeruleus Limbic system - Amygdala - Hippocampus Modified from Vandewalle et al. Trends Cogn Sci, 2009 Light has many non-visual biological effects in humans (only peer reviewed data) • Synchronization of circadian rhythms • Suppression of the «darkness hormone» melatonin • Alerting and enhancing of cognitive performance • Regulation of pupil size • Enhancing mood (antidepressant) • Enhancing physical performance in top athletes • Light color modulates mental effort Conclusion • Light rules our body via its non-visual effects • Blue wavelengths -- which are beneficial during daylight hours because they boost attention, reaction times, mood, and physical performance -- are most disruptive at night • The proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown Non-visual lighting solutions should be: Dynamic • Intensity and duration • Spectral composition • According to time of day Individual • Age • Gender • Chronotype (early vs.late people) Wanted Intelligent human centric lighting to adapt our illuminated surroundings such that we do not jeopardize quality of life and health but positively influence our sleep, circadian physiology, cognition and well-being Human Centric Lighting enter the room by Human centric lighting supports your health and promotes Acknowledgements Centre for Chronobiology www.chronobiology.ch • Antoine Viola, PhD • Christina Schmidt, PhD • Mirjam Münch, PhD • Sarah Chellappa, PhD • Vivien Bromundt, PhD • Jakub Späti, PhD • Sylvia Frey, PhD • Virginie Gabel • Micheline Maire • Carolin Reichert • Stephanie van der Lely EU IP Swiss Federal Office for Public Health Daimler-Benz Foundation .
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