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International Journal of Endocrinology
Volume 2012 (2012), Article ID 530726, 6 pages
http://dx.doi.org/10.1155/2012/530726
Clinical Study

Light Modulates Leptin and Ghrelin in Sleep-Restricted Adults

Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180-3352, USA

Received 1 June 2012; Revised 24 July 2012; Accepted 25 July 2012

Academic Editor: Barry Posner

Copyright © 2012 Mariana G. Figueiro et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Acute and chronic sleep restrictions cause a reduction in leptin and an increase in ghrelin, both of which are associated with hunger. Given that light/dark patterns are closely tied to sleep/wake patterns, we compared, in a within-subjects study, the impact of morning light exposures (60 lux of 633-nm [red], 532-nm [green], or 475-nm [blue] lights) to dim light exposures on leptin and ghrelin concentrations after subjects experienced 5 consecutive days of both an 8-hour (baseline) and a 5-hour sleep-restricted schedule. In morning dim light, 5-hour sleep restriction significantly reduced leptin concentrations compared to the baseline, 8-hour sleep/dim-light condition ( 𝑡 1 , 3 2 = 2.9; 𝑃 = 0 . 0 0 7 ). Compared to the 5-hour sleep/dim-light condition, the red, green, and blue morning light exposures significantly increased leptin concentrations ( 𝑡 1 , 3 2 = 5.7; 𝑃 < 0 . 0 0 0 1 , 𝑡 1 , 3 2 = 3.6; 𝑃 = 0 . 0 0 1 , and 𝑡 1 , 3 2 = 3.0; 𝑃 = 0 . 0 0 5 , resp.). Morning red light and green light exposures significantly decreased ghrelin concentrations ( 𝑡 1 , 3 2 = 3.3; 𝑃 < 0 . 0 0 3 and 𝑡 1 , 3 2 = 2.2; 𝑃 = 0 . 0 4 , resp.), but morning blue light exposures did not. This study is the first to demonstrate that morning light can modulate leptin and ghrelin concentrations, which could have an impact on reducing hunger that accompanies sleep deprivation.