A master thesis from Aalborg University
Exploring light parameters for night shift workers
Term
4. Term
Education
Publication year
2017
Submitted on
2017-06-02
Pages
92 pages
Abstract
Working night shifts is taxing on the human circadian rhythm and a study from 2017 shows that there is 26% increased mortality rate amongst the Danish nurse cohort due to night shift work. The increased mortality rate is thought to be caused by a disruption in the human endocrinology that happens working night shifts. Light can be used as a tool, to help stimulate the hormones melatonin and cortisol, to support the natural circadian rhythm. The thesis explores the possibilities of finding a lighting condition, for night shift workers, which provides both visual comfort and low circadian stimulation. The main methods used includes a case analysis of a rehabilitation center with interviews of three night shift workers, a theoretical investigation on how lighting affects the circadian system and a laboratory experiment (n=30) evaluating the performance and preference of three different lighting conditions with varying degrees of circadian stimulation, based on a Circadian Stimulus metric. Red light is found to have the lowest effect on the circadian rhythm but the experiment shows that it does not provide satisfying visual comfort. A broad spectrum lighting condition, with UV-A (380-420 nm) instead of blue wavelengths, is found to improve visual comfort, while keeping circadian stimulation low. The thesis ends up by investigating different lighting parameters when designing for night shift workers and finds that there are no lighting conditions, which can fulfill both image forming (visual) and non-image forming (health related) lighting criteria. Although, good compromises can be made, based on the context, to offer visual comfort and at the same time reduce melatonin suppression during the night.
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