The spectral composition of evening light and individual differences in the suppression of melatonin and delay of sleep in humans
Article first published online: 24 OCT 2011
© 2011 John Wiley & Sons A/S
Journal of Pineal Research
Volume 53, Issue 1, pages 47–59, August 2012
How to Cite
Santhi, N., Thorne, H. C., van der Veen, D. R., Johnsen, S., Mills, S. L., Hommes, V., Schlangen, L. J.M., Archer, S. N. and Dijk, D.-J. (2012), The spectral composition of evening light and individual differences in the suppression of melatonin and delay of sleep in humans. Journal of Pineal Research, 53: 47–59. doi: 10.1111/j.1600-079X.2011.00970.x
- Issue published online: 5 JUL 2012
- Article first published online: 24 OCT 2011
- Accepted manuscript online: 20 SEP 2011 05:03PM EST
- Received July 26, 2011; Accepted September 15, 2011.
- polychromatic light
Abstract: The effect of light on circadian rhythms and sleep is mediated by a multi-component photoreceptive system of rods, cones and melanopsin-expressing intrinsically photosensitive retinal ganglion cells. The intensity and spectral sensitivity characteristics of this system are to be fully determined. Whether the intensity and spectral composition of light exposure at home in the evening is such that it delays circadian rhythms and sleep also remains to be established. We monitored light exposure at home during 6–8 wk and assessed light effects on sleep and circadian rhythms in the laboratory. Twenty-two women and men (23.1 ± 4.7 yr) participated in a six-way, cross-over design using polychromatic light conditions relevant to the light exposure at home, but with reduced, intermediate or enhanced efficacy with respect to the photopic and melanopsin systems. The evening rise of melatonin, sleepiness and EEG-assessed sleep onset varied significantly (P < 0.01) across the light conditions, and these effects appeared to be largely mediated by the melanopsin, rather than the photopic system. Moreover, there were individual differences in the sensitivity to the disruptive effect of light on melatonin, which were robust against experimental manipulations (intra-class correlation = 0.44). The data show that light at home in the evening affects circadian physiology and imply that the spectral composition of artificial light can be modified to minimize this disruptive effect on sleep and circadian rhythms. These findings have implications for our understanding of the contribution of artificial light exposure to sleep and circadian rhythm disorders such as delayed sleep phase disorder.