Light and dark, activity and rest in day shift and rotating shift nurses

Transcription

1 Light and dark, activity and rest in day shift and rotating shift nurses M.S. Rea 1, A. Bierman 1, M.G. Figueiro 1, Y. Zhou 1, E. Schernhammer 2 Nineteenth Annual Meeting of The Society for Light Treatment and Biological Rhythms (SLTBR) Copenhagen, Denmark June 28-30, Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY, USA 2 Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA 1

2 Original idea Melatonin Hypothesis (Stevens, 1987) Suppression of melatonin was hypothesized to increase production of estrogens in the ovaries, which in turn should stimulate the turnover of breast epithelial cells, thereby increase the likelihood of cancer Light of the right characteristics should suppress melatonin at night Rotating night shift workers are exposed to light at night, thus their melatonin concentration should be reduced, resulting in higher risk of breast cancer 2

3 Current ideas Breast cancer risk in rotating shift women is greater than in day shift women Schernhammer et al., 2001, Hansen, 2006 Light at night suppresses melatonin in animal models and increases the rate of cancer growth Blask et al., 1991; Blask et al., 2005 Circadian disruption by light can negatively affect cell proliferation and ontogeny in animal models Wood et al.,

4 Current uncertainties Undefined light-dark levels and patterns for all women Unknown levels of circadian disruption for all women Rest-activity Melatonin Gene expression SCN Mammary No formal links between human light-dark levels and patterns and those in animal models for cancer research 4

5 What are our contributions? Developed an instrument to measure circadian light and dark levels and patterns for humans as well as activity patterns The Daysimeter Characterizing the light and dark levels and patterns for day and rotating shift nurses as well as their activity patterns Linking Daysimeter data to outcome measures for nurses health study Will begin to bridge human light/activity patterns to those for animal models 5

6 Daysimeter Development 6

7 Current Daysimeter Light sensors Activity monitor 7

8 Spectrum Spectral Response Functions for (Equal Energy) White Light and Monochromatic Light Modeled Spectral Sensitivity for Equal Energy Spectrum (to give 35% melatonin suppression) 1 relative value (arb. units) V λ V λ wavelength (nm) Sponsor: Office of VP for Research Rensselaer Polytechnic Institute Figueiro et al., 2004 Rea et al.,

9 Circadian light transfer function Figueiro, et al

10 Light and activity for seven days Day shift nurse Time (days) Rotating shift nurse Time (days) 10

11 Light and activity for seven days (39 subjects, 30 day shifts, 9 rotating shifts) 11

12 Day shift nurse 0 Entrained 0 12

13 Rotating shift nurse 0 Disrupted 0 13

14 Disruption Based on FFT distortion analyses (43 subjects, 32 day shifts, 11 rotating shifts) 14

15 What is next (near future)? Correlate Daysimeter data with Sleep quality questionnaire Body mass index (BMI) Subjective impressions of the lighted environment Morningness/eveningness scale Urine melatonin 15

16 How can we bridge human circadian light exposures to circadian light exposures in nocturnal rodents? 16

17 What is next? Entrained Disrupted Human Rodent 17

18 Thank you! The authors gratefully acknowledge the contributions of the following Lighting Research Center associates: John Bullough, Dennis Guyon, Terry Klein, Conan O RourkeO NIH# 1R01OH