Integrative Lighting Design Applied Reduced Sleepiness Perception Among Night Shift Workers

Keywords

night shift worker - sleep - activity/rest rhythm - integrative lighting - light

Introduction: Despite the growing relevance of the urban night economy, inadequate time of exposure to light can compromise the health of night shift workers. In this sense, circadian adjustment is important for improving tolerance to night work and can be achieved through the proper stimulus of intrinsically photosensitive retinal ganglion cells (ipRGC) by light.

Objective: The aim of this study was to comparably verify the light exposure effects in the workplace, before and after a lighting tailored intervention, on variables related to the activity/rest rhythm and sleep in night shift workers.

Methods: An exploratory study was conducted based on a case study with a quantitative empirical approach. The lighting conditions was changed by a non-pharmacological intervention, through the installation of desk luminaires developed exclusively for this research. The collection of behavioral variables took place in two phases, one phase before and the other after the lighting intervention, both utilizing an actigraph, worn on the nondominant wrist and completion of a daily activity protocol. Each phase was done in a period of 9 days, including two days off. The analysis was performed using mean comparison tests (parametric and non-parametric) in order to compare the variables of interest before versus after the implementation of the new lighting exposure.

Results: The sample of this study, consisting of 10 participants (8 female, Mage = 29.6, SDage = 7.31, range = 21-46), showed an increase in the main sleep latency during days off, with the use of the desk luminaire (p=0.02). Additionally, a 25.16% increase in subjective sleepiness (obtained with Karolinska Sleepiness Scale) was noted at 1:00am (p=0.03) and a 10.55% decrease at 5:00am (p=0.04) after the lighting intervention. Despite the fact that at both phases was observed an increase in the sleepiness at the end of the shift (72.51% before and 23.28% with the luminaire), the results seen were 3.11 fold lower with the luminaire light exposure during night work. No statistically significant changes were observed in the measures of activity/rest rhythm.

Conclusion: Even though no benefits were perceived in the objective measures of sleep and in the activity/rest rhythm, the tailored lighting design appeared to benefit the subjective measures of sleepiness at the end of the night shift.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
16 September 2025