A Working Threshold for Acute Nocturnal Melatonin Suppression from “White” Light Sources used in Architectural Applications
Mark S. Rea* and Mariana G. Figueiro
Lighting Research Center, Rensselaer Polytechnic Institute, Troy, New York, USA
- *Corresponding Author:
- Mark S. Rea, PhD
Lighting Research Center
Rensselaer Polytechnic Institute
Troy, New York 12180, USA
Tel: 518 687 7100
Fax: 518 687 7120
E-mail: [email protected]
Received date: July 22, 2013; Accepted date: September 11, 2013; Published date: September 20, 2013
Citation: Rea MS, Figueiro MG (2013) A Working Threshold for Acute Nocturnal Melatonin Suppression from “White” Light Sources used in Architectural Applications. J Carcinogene Mutagene 4:150 doi: 10.4172/2157-2518.1000150
Copyright: © 2013 Rea MS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Retinal light exposures can decrease melatonin production at night. Since nocturnal melatonin suppression by light has been implicated as an endocrine disruptor and linked to certain diseases, such as diabetes, obesity and cancer, it is important to be able to estimate a threshold light level needed to reliably suppress melatonin. The present study was designed to develop a working threshold for melatonin suppression from “white” light that might be experienced by people in their living environments. Twenty-eight subjects participated in two studies. In addition to dark, control nights, subjects were exposed to 8, 22, and 60 lux at the cornea (study 1, n=14) and to 60, 200, and 720 lux (study 2, n=14) of a “warm white” light source (correlated color temperature of 2670 K). These corneal illuminance levels translate to modeled melatonin suppression levels of 1%, 2%, 6%, 19%, and 42%. In both studies, participants came to the laboratory for four nights, separated by one week. One blood sample was drawn in dim light at midnight and another blood sample was drawn after 60-minute exposure to each light condition (including dark). Using an orthodox statistical criterion for a Type I error of α< 0.05, only the 200 lux and the 720 lux exposures produced significant suppression levels (19% and 37%, respectively). Based upon a criterion modeled suppression level of 5% for a “cool white” light (6500 K), a corneal light exposure of 30 lux for 30 minutes from “white” light sources used in most architectural lighting applications is proposed as a conservative hypothesized working threshold for nocturnal melatonin suppression.