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

• Published in: Physiology & behavior Vol. 177; pp. 221 - 229
• Main Authors: Rahman, Shadab A., St. Hilaire, Melissa A., Lockley, Steven W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2017
• Subjects: Alertness; Brain - physiology; Circadian; Circadian Rhythm - physiology; Circadian Rhythm - radiation effects; Cross-Over Studies; Electroencephalography; Female; females; fluorescence; fluorescent lighting; Humans; Light; Lighting; Male; Melatonin; Melatonin - metabolism; Polysomnography; Psychiatry; Sleep; Sleep - physiology; Sleep - radiation effects; spectral analysis; Spectrum; Time Factors; Wakefulness - physiology; Wakefulness - radiation effects; Young Adult; Alertness; Melatonin; Sleep; Circadian; Light; Spectrum
• ISSN: 0031-9384; 1873-507X; 1873-507X
• DOI: 10.1016/j.physbeh.2017.05.002

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. •Pre-bedtime light exposure disrupts sleep and circadian rhythms.•We tested whether these disruptions are attenuated under dim blue-depleted light.•Blue-depleted ambient light reduced melatonin suppression and alertness.