Indirect blue light does not suppress nocturnal salivary melatonin in humans in an automobile setting
Article first published online: 23 JUN 2009
© 2009 The Authors. Journal compilation © 2009 John Wiley & Sons A/S
Journal of Pineal Research
Volume 47, Issue 2, pages 143–146, September 2009
How to Cite
Lerchl, A., Schindler, C., Eichhorn, K., Kley, F. and Erren, T. C. (2009), Indirect blue light does not suppress nocturnal salivary melatonin in humans in an automobile setting. Journal of Pineal Research, 47: 143–146. doi: 10.1111/j.1600-079X.2009.00691.x
- Issue published online: 2 AUG 2009
- Article first published online: 23 JUN 2009
- Received March 30, 2009; accepted May 8, 2009.
- light at night;
- shift work
Abstract: In 2007, the International Agency for Research on Cancer (IARC) classified shift work that involves circadian disruption as being probably carcinogenic to humans (Group 2A). In this context, light exposure during the night plays a key role because it can suppress nocturnal melatonin levels when exposures exceed a certain threshold. Blue light around 464 nm is most effective in suppressing melatonin because of the spectral sensitivity of melanopsin, a recently discovered photopigment in retinal ganglion cells; the axons of these cells project to the suprachiasmatic nucleus, a circadian master clock in the brain. Due to advances in light technologies, normal tungsten light bulbs are being replaced by light-emitting diodes which produce quasi-monochromatic or white light. The objective of this study was to assess whether the light–melanopsin–melatonin axis might be affected in automobiles at night which employ the new generation diodes. To this end, we have tested in an experimental automobile setting whether indirect blue light (λmax = 465 nm) at an intensity of 0.22 or 1.25 lx can suppress salivary melatonin levels in 12 male volunteers (age range 17–27 years) who served as their own controls. Daytime levels were low (2.7 ± 0.5 pg/mL), and night-time levels without light exposure were high (14.5 ± 1.1 pg/mL), as expected. Low-intensity light exposures had no significant effect on melatonin levels (0.22 lx: 17.2 ± 2.8 pg/mL; P > 0.05; 1.25 lx: 12.6 ± 2.0 pg/mL; P > 0.05). It is concluded that indirect blue light exposures in automobiles up to 1.25 lx do not cause unintentional chronodisruption via melatonin suppression.