NDLI: Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Khalsa, Sat Bir S. Rajaratnam, Shantha M. W. Gooley, Joshua J. Van Reen, Eliza Lockley, Steven W. Czeisler, Charles A. Zeitzer, Jamie M. Chamberlain, Kyle Smith, Kurt A.
Description	Country affiliation: United States Author Affiliation: Gooley JJ ( Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Avenue, Boston, Massachusetts 02115, USA. gmsjjg@nus.edu)
Abstract	CONTEXT: Millions of individuals habitually expose themselves to room light in the hours before bedtime, yet the effects of this behavior on melatonin signaling are not well recognized. OBJECTIVE: We tested the hypothesis that exposure to room light in the late evening suppresses the onset of melatonin synthesis and shortens the duration of melatonin production. DESIGN: In a retrospective analysis, we compared daily melatonin profiles in individuals living in room light (<200 lux) vs. dim light (<3 lux). PATIENTS: Healthy volunteers (n = 116, 18-30 yr) were recruited from the general population to participate in one of two studies. SETTING: Participants lived in a General Clinical Research Center for at least five consecutive days. INTERVENTION: Individuals were exposed to room light or dim light in the 8 h preceding bedtime. OUTCOME MEASURES: Melatonin duration, onset and offset, suppression, and phase angle of entrainment were determined. RESULTS: Compared with dim light, exposure to room light before bedtime suppressed melatonin, resulting in a later melatonin onset in 99.0% of individuals and shortening melatonin duration by about 90 min. Also, exposure to room light during the usual hours of sleep suppressed melatonin by greater than 50% in most (85%) trials. CONCLUSIONS: These findings indicate that room light exerts a profound suppressive effect on melatonin levels and shortens the body's internal representation of night duration. Hence, chronically exposing oneself to electrical lighting in the late evening disrupts melatonin signaling and could therefore potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis.
ISSN	0021972X
e-ISSN	19457197
DOI	10.1210/jc.2010-2098
Journal	The Journal of Clinical Endocrinology & Metabolism
Issue Number	3
Volume Number	96
Language	English
Publisher	Oxford University Press
Publisher Date	2011-03-01
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Melatonin Blood Adolescent Physiology Time Factors Research Support, N.i.h., Extramural Research Support, U.s. Gov't, Non-p.h.s. Discipline Endocrinology Discipline Metabolism
Content Type	Text
Resource Type	Article
Subject	Biochemistry (medical) Endocrinology, Diabetes and Metabolism Clinical Biochemistry Biochemistry Endocrinology

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