Acute effects of different light spectra on simulated night-shift work without circadian alignment

ABSTRACT

Short-wavelength and short-wavelength-enhanced light have a strong impact on night-time working performance, subjective feelings of alertness and circadian physiology. In the present study, we investigated acute effects of white light sources with varied reduced portions of short wavelengths on cognitive and visual performance, mood and cardiac output.Thirty-one healthy subjects were investigated in a balanced cross-over design under three light spectra in a simulated night-shift paradigm without circadian adaptation.Exposure to the light spectrum with the largest attenuation of short wavelengths reduced heart rate and increased vagal cardiac parameters during the night compared to the other two light spectra without deleterious effects on sustained attention, working memory and subjective alertness. In addition, colour discrimination capability was significantly decreased under this light source.To our knowledge, the present study for the first time demonstrates that polychromatic white light with reduced short wavelengths, fulfilling current lighting standards for indoor illumination, may have a positive impact on cardiac physiology of night-shift workers without detrimental consequences for cognitive performance and alertness.

KEYWORDS:

• Short wavelength
• light spectrum
• shift work
• simulated night-shift
• sustained attention
• working memory
• mood
• alertness
• visual performance
• heart rate
• heart rate variability

Acknowledgements

We thank the volunteers for their participation and we are grateful for practical assistance of Siegmund Staggl, Markus Laner and Stefanie Mair in the course of study execution.

Declaration of interest

This study obtained financial support from the Austrian Research Promotion Agency (Grant No. 825348/k-Licht). The authors report no conflicts of interest. Two authors (M.C., W.P.) are employed at the lighting design- and R&D-company Bartenbach GmbH.