Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

NIOSHTIC-2 Publications Search

Search Results

Measurements of light at night (LAN) for a sample of female school teachers.

Authors
Rea-MS; Brons-JA; Figueiro-MG
Source
Chronobiol Int 2011 Oct; 28(8):673-680
NIOSHTIC No.
20040284
Abstract
Epidemiological studies have shown an association between rotating shiftwork and breast cancer (BC) risk. Recently, light at night (LAN) measured by satellite photometry and by self-reports of bedroom brightness has been shown to be associated with BC risk, irrespective of shiftwork history. Importance has been placed on these associations because retinal light exposures at night can suppress the hormone melatonin and/or disrupt circadian entrainment to the local 24-h light-dark cycle. The present study examined whether it was valid to use satellite photometry and self-reports of brightness to characterize light, as it might stimulate the circadian system and thereby affect BC incidence. Calibrated photometric measurements were made at the bedroom windows and in the bedrooms of a sample of female school teachers, who worked regular dayshifts and lived in a variety of satellite-measured sky brightness categories. The light levels at both locations were usually very low and were independent of the amount of satellite-measured light. Calibrated photometric measurements were also obtained at the corneas of these female school teachers together with calibrated accelerometer measurements for seven consecutive days and evenings. Based upon these personal light exposure and activity measurements, the female teachers who participated in this study did not have disrupted light-dark cycles like those associated with rotating shiftworkers who do exhibit a higher risk for BC. Rather, this sample of female school teachers had 24-h light-dark and activity-rest patterns very much like those experienced by dayshift nurses examined in an earlier study who are not at an elevated risk of BC. No relationship was found between the amount of satellite-measured light levels and the 24-h light-dark patterns these women experienced. It was concluded from the present study that satellite photometry is unrelated to personal light exposures as they might affect melatonin suppression and/or circadian disruption. More generally, photometric devices calibrated in terms of the operational characteristics of the human circadian system must be used to meaningfully link LAN and BC incidence.
Keywords
Humans; Women; Age-groups; Shift-work; Cancer; Lighting; Light-source; Retinal-disorders; Circadian-rhythms; Breast-cancer; Exposure-limits; Exposure-levels; Author Keywords: Breast cancer; Circadian light; Circadian light levels; Light pollution; Melatonin
Contact
Mark S. Rea, PhD, Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180
CODEN
CHBIE4
Publication Date
20111001
Document Type
Journal Article
Email Address
ream@rpi.edu
Funding Type
Grant
Fiscal Year
2012
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-008171
Issue of Publication
8
ISSN
0742-0528
Source Name
Chronobiology International
State
NY; MA
Performing Organization
Brigham and Women's Hospital
TOP