The effects of spectral tuning of evening ambient light on melatonin suppression, alertness and sleep

Physiol Behav. 2017 Aug 1;177:221-229. doi: 10.1016/j.physbeh.2017.05.002. Epub 2017 May 1.


We compared the effects of bedroom-intensity light from a standard fluorescent and a blue- (i.e., short-wavelength) depleted LED source on melatonin suppression, alertness, and sleep. Sixteen healthy participants (8 females) completed a 4-day inpatient study. Participants were exposed to blue-depleted circadian-sensitive (C-LED) light and a standard fluorescent light (FL, 4100K) of equal illuminance (50lx) for 8h prior to a fixed bedtime on two separate days in a within-subject, randomized, cross-over design. Each light exposure day was preceded by a dim light (<3lx) control at the same time 24h earlier. Compared to the FL condition, control-adjusted melatonin suppression was significantly reduced. Although subjective sleepiness was not different between the two light conditions, auditory reaction times were significantly slower under C-LED conditions compared to FL 30min prior to bedtime. EEG-based correlates of alertness corroborated the reduced alertness under C-LED conditions as shown by significantly increased EEG spectral power in the delta-theta (0.5-8.0Hz) bands under C-LED as compared to FL exposure. There was no significant difference in total sleep time (TST), sleep efficiency (SE%), and slow-wave activity (SWA) between the two conditions. Unlike melatonin suppression and alertness, a significant order effect was observed on all three sleep variables, however. Individuals who received C-LED first and then FL had increased TST, SE% and SWA averaged across both nights compared to individuals who received FL first and then C-LED. These data show that the spectral characteristics of light can be fine-tuned to attenuate non-visual responses to light in humans.

Keywords: Alertness; Circadian; Light; Melatonin; Sleep; Spectrum.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Brain / physiology
  • Circadian Rhythm / physiology
  • Circadian Rhythm / radiation effects
  • Cross-Over Studies
  • Electroencephalography
  • Female
  • Humans
  • Light*
  • Lighting*
  • Male
  • Melatonin / metabolism*
  • Polysomnography
  • Sleep / physiology
  • Sleep / radiation effects*
  • Time Factors
  • Wakefulness / physiology
  • Wakefulness / radiation effects*
  • Young Adult


  • Melatonin