0240 Nocturnal Melatonin Suppression In Adolescents And Adults For Different Levels, Spectra And Durations Of Light Exposure

• Published in: Sleep (New York, N.Y.) Vol. 42; no. Supplement_1; p. A99
• Main Authors: Nagare, Rohan M, Rea, Mark S, Plitnick, Barbara A, Figueiro, Mariana G
• Format: Journal Article
• Language: English
• Published: Westchester Oxford University Press 13.04.2019
• Subjects: Age; Light; Lighting; Melatonin; Teenagers
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsz067.239

Introduction An altered phase relationship between the circadian system and the sleep-wake cycle can be detrimental to sleep quantity, quality, and health. The human circadian system is primarily regulated by the 24-hour light-dark cycle incident on the retina. Although, limited data related to the combined effects of various lighting characteristics has impeded the development of circadian-effective light-treatment methods. The present study intended to describe the effects of lighting exposure duration on nocturnal melatonin suppression, a circadian biomarker, for 2 contrasting spectra delivering a range of indoor light levels. Another goal was to examine whether identical light exposures can differentially affect the circadian systems of different age groups. They study also intended to empirically estimate an absolute threshold for discussing light’s impact on acute melatonin suppression. Methods Melatonin suppression was measured for 18 adolescents (ages: 13-18 years) and 22 adults (ages: 24-55 years) for 2 white light spectra (2700 K and 6500 K, 40-1000 lux), over a range of light exposure durations (0.5-3.0 h, starting 23:00). Lighting apparatus comprised of RGB color-tunable, diffused linear LED light bars mounted on participants’ desks. Results Results showed that light’s incremental effectiveness for suppressing melatonin diminishes with increasing exposure duration for both age groups and both light sources. Threshold criterion of 10% suppression was reached for lower light levels at only longer exposure durations. Depending upon the age-group, the 6500 K source required 71-85 lux for a 1-h exposure and 36-49 lux for 3-h exposure to reach the threshold criterion. Yet, the results do not statistically corroborate our hypothesis that adolescents exhibit greater circadian sensitivity to short-wavelength radiation compared to adults. Spectral sensitivity of acute melatonin suppression was found to not change with exposure duration. Conclusion Dose-response curves generated for each spectra, age-group and duration can guide circadian-lighting recommendations in applications such as offices, schools, residences, and healthcare facilities. Earlier proposed melatonin suppression threshold of 30 lux for 30 min for white light, by Figueiro and colleagues, appears to be an acceptable, if conservative, recommendation. Support (If Any)