Christian Cajochen, PhD Centre for Chronobiology

Psychiatric Hospital of the University of Basel, Switzerland

Human Centric Lighting - beyond our eyes: the non-visual impact of light

European Lighting Summit, Brussels, 30.03.2017

Thomas Edison was probably wrong

Buttgereit, Smolen, Coogan, Cajochen, Nat Rev Rheumatol, 2015

Light is the most important Zeitgeber !

Induction of a Phase Delay in the Human Circadian Melatonin Rhythm by Light (10’000 lux for 6.5 h)

Khalsa et al., J Physiol (London) 2003

Time of Day

12 24 12 24 12 24 12 24 12

Pla

sma

Me

lato

nin

(p

Mo

l/L)

0

100

200

300

400 Light

Midpoint 4:45

Midpoint 8:21

Light and human circadian rhythms Melatonin as the best circadian marker in humans

Sleep period

Retina -4

-3

-2

-1

0

1

2

3

4

0 3 6 9 12 15 18 -3 -6 -9 -12 -15 -18

Initial Phase (time relative to DLMO=0)

Ph

ase

sh

ift

(h)

Khalsa, et al., J Physiol (London) 2003

6.7 hours 10’000 lux polychromatic white light

Phase-Response Curve

Light and circadian phase

«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

Time of Day (h)

36.0

36.5

37.0

37.5

200

300

100 Plasma Melatonin

(pmol/liter)

Core Body Temperature (°C)

Blind Person

12 18 24 6 12 18 24 6 12

36.0

36.5

37.0

37.5

200

300

100

Core Body Temperature (°C)

Plasma Melatonin (pmol/liter)

12 18 24 6 12 18 24 6 12

Czeisler et al., New Engl Med 1995

Time of Day (h)

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

20

0 420 460 481 500 506 515 540 560 580

Wavelength (nm)

Co

rre

ct A

nsw

er

(%)

Nach Zaidi et al., Curr Biol, 2007

SCN (circadian Pacemaker)

Retina Cones

Eye A dual sensory organ

Rods

Non-classical Photoreceptor intrinsic photosensitive retinal ganglion

cells (iPRGs, Melanopsin)

Hattar et al. Science, 2002 Berson et al. Science, 2002

Retina -4

-3

-2

-1

0

1

2

3

4

0 3 6 9 12 15 18 -3 -6 -9 -12 -15 -18

Initial Phase (time relative to DLMO=0)

Ph

ase

sh

ift

(h)

Khalsa, et al., J Physiol (London) 2003

6.7 hours 10’000 lux polychromatic white light

Rüger, et al., J Physiol (London) 2013

75 % of the resetting response

6.5 hours blue light (480 nm) 11.8 μWcm−2, 11.2 lux)

Phase-Response Curve

Light and circadian phase

0 1 2 3

Time elapsed from light onset (h)

Sle

ep

Re

spo

nse

(m

in)

0

30

60

Lights ON Lights OFF

Wildtype

Melanopsin knockout

According to Muindi et al., Front Syst Neurosci, 2014

Melanopsin aDTA

Acute sleep induction by light in nocturnal mice

Illuminance (lux)

10 100 1000 10000

Subjective Alertness

5

10

15

20

25

mo

re a

lert

Cajochen et al., Beh Brain Res. 2000

120 lux !

Acute alerting effects of light in diurnal humans

Kar

olin

ska

Sle

ep

ine

ss S

cale

(K

SS)

6

7

8

The human alerting response to light is blue-shifted

% S

leep

ines

s C

han

ge

0 =

pre

-lig

ht

0

10

20

30

40

50

4

5

6

Kar

olin

ska

Sle

ep

ine

ss S

cale

(K

SS)

Cajochen et al., Sleepiness and human impact assessment Book chapter, Springer, 2014

Monochromatic light Energy Saving Lamps Computer Screens

Declarative Learning (Word pairs)

Non-LED

LED Screen

Cajochen et al., J Appl Physiol. 2011

Correctly identified new word pairs

45

50

55

60

65

70

*

* P <0.05

Wavelength (nm)

Wavelength (nm)

Re

lati

ve C

on

trib

uti

on

R

ela

tive

Co

ntr

ibu

tio

n

Why is this relevant: Light bulb versus LED

Ja

nicht beantwortet

Use of smartphones 1 hour prior bedtime

99% yes

irgendwo in derWohnung

irgendwo im Zimmer

auf dem Nachttisch

im Bett

nicht beantwortet

Where do you keep your smartphone during night?

60%

14% 23%

97% in bedroom

nie

selten

gelegentlich

häufig

nicht beantwortet

How often do you use your smartphone after «Lights off»

49%

25%

15%

10%

74% occasionally-often

Smartphone use in adolescents (14-20 years)

Strube et al. Somnologie, 2016

99 %

400 450 500 550 600 650 700

0

0.2

0.4

0.6

0.8

1.0 R

ela

tive

Am

plit

ud

e

Wavelength

“Ipad” versus “Blue-blockers” Transmission Spectra

iPad Orange-tinted glasses (blue blockers)

Time of day

pg/

ml

0

2

4

6

8

10

12

14

16

Dim Dim

Sle

ep

LED/glasses Dark

*

* *

* Blue Blockers for one week

Clear Lenses for one week

Evening Melatonin Levels in Adolescents

van der Lely et al., J Adolesc Health, 2014

Sle

ep

Time of day

KSS

-sco

re

2

3

4

5

6

7

8

Blue Blockers for one week

Clear Lenses for one week

* *

Dim LED/glasses Dim

Sle

ep

*

Subjective Sleepiness in Adolescents

Blocking blue light in the evening

Dark

van der Lely et al., J Adolesc Health, 2014

Modified from Vandewalle et al. Trends Cogn Sci, 2009

Light is not just for vision

Cortex

Thalamus

Hypothalamus

Brainstem - Locus coeruleus

Limbic system - Amygdala - Hippocampus

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

• 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

Conclusion

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)

Conventional LED vs. daylight LED

Daylight LED Conventional LED

Blue is not blue

Wavelength (nm)

360 390 420 450 480 510 540 570 600 630 660 690 720 750 780

Arb

itra

ry U

nit

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Wavelength (nm)

360 390 420 450 480 510 540 570 600 630 660 690 720 750 780

Arb

itra

ry U

nit

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Difference

Conventional LED

Daylight LED

The same photopic lux: 100 and the same colour temperature: 3700 K

for both light conditions

melanopic lux [m-lx]

or [z-lx]

67.9

56.9

Intensity

illuminance

[lx, phot.]

Intensity

power density

[mW/cm2]

97 0.037

98 0.029Conv. LED

Daylight LED

Conventional LED vs. daylight LED

Cognitive Test Battery

10 14 18 22

Baseline Night

Treatment Night

24 8 10 14 18 22 24 8

Conv. LED

10 14 18 22

18 22

Time of day

Baseline Night

Treatment Night

24 8 10 14 18 22 24 8

Daylight LED

10 14 18 22

18 22

Subjective Rating of Light Quality(Brightness and Colour Temperature)

Lig

ht

Qu

ality

wo

rse

b

ett

er

3.0

3.5

4.0

4.5

5.0

Conv. LED

Daylight LED

*

The same photopic lux: 100 and the same colour temperature: 3700 K

for both light conditions

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

Wanted

Human Centric Lighting

enter

the room by

Human centric lighting supports your health

and promotes

Acknowledgements

Centre for Chronobiology • Antoine Viola, PhD

• Sarah Chellappa, PhD

• Virginie Gabel, PhD

• Mirjam Münch, PhD

• Vivien Bromundt, PhD

• Van der Lely, MS

• Sylvia Frey, PhD

• Doreen Anders, PhD

• Weibel, Janine, MS

• Basishvili, Tamar, PhD

• Christina Schmidt, PhD

• Micheline Maire, PhD

• Carolin Reichert, PhD

• Jakub Späti, PhD

Fraunhofer Institute • Oliver Stefani

Swiss Federal Office for Public Health Daimler-Benz Foundation EU IP