- Project number: F 2496
- Institution: Federal Institute for Occupational Safety and Health (BAuA) / Technische Universität Berlin
- Status: Completed Project
Description:
In Germany, increasingly more people are working night shifts. This exposes them to light when the human body expects darkness for normal function. On the one hand, light is necessary for good visibility of work tasks and the prevention of accidents at work. On the other hand, light at night disrupts the body’s natural day-night rhythm - this is referred to as desynchronisation. Desynchronisation is in turn associated with negative long-term health effects, such as obesity or cardiovascular problems. In addition, the "light-at-night" hypothesis links night-time suppression of the sleep hormone, melatonin, to an increased risk of cancer.
This project examined whether the spectral and spatial characteristics of night shift lighting could be designed to minimise melatonin suppression, while supporting alertness. For this purpose, a subject study was conducted. The study aimed for realistic conditions corresponding with lighting conditions as they occur in e.g. control rooms. In addition to illuminance and spectral composition, lighting direction was varied, and the suppression of melatonin production and various alertness measures were assessed.
Lighting direction and melanopic irradiance (the physical quantity that describes non-visual effectiveness of light) had a significant impact on melatonin suppression without adversely affecting alertness. Hence, lighting situations for night shift workers should be designed with light of low melanopic irradiance and higher illuminance. This way, unwanted melatonin suppression can be reduced while maintaining alertness. To further minimise melatonin suppression, light with a high melanopic content should come from the workers’ lower field of view.