Melatonin suppression by blue narrow-band light emitting diodes in healthy subjects – comparison with bright white light

Background: In 2002, blue-light-sensitive retinal ganglion cell photoreceptors have been discovered by Berson et al. Blue light seems to be very effective in suppression of melatonin (mel) secretion. The aim of this study was to compare the efficacy of blue light emitting diode units with broad spectrum white light in suppression of mel secretion and well-being in healthy subjects. Methods: Secretion profiles of mel were studied in blood plasma of 30 healthy morning-type subjects (15m/15f) in three consecutive days. The subjects were kept under dim illumination (<10lx) from 19:00 to 22:30 (control day 1). On day 2 and 3, after 1,5h in dim light, the subjects were exposed for 60min (20:30–21:30) to white light (250lx) or blue light (12,15µW/cm²), respectively. Sleepiness and well-being were self-rated before and after each session. Results: In all subjects, 5lx (photopic) or 116lx (scotopic) illuminance of monochromatic blue light was sufficient to suppress mel secretion within 60min. The effect was greater when compared to 250lx white light. There were gender-related differences. Whereas white light was without any effects on sleepiness and well-being, blue light caused in 30% of investigated subjects a significant activation and reduction in sleepiness. Conclusion: Further examination of more subjects seems to be important to characterize different effects of blue and white light, as well as differences between males and females.

This study was supported by TurboLite Vetriebs GmbH