Light therapy glasses during night shift work: a field study

Abstract

Abstract Background Night shift work leads to severe short- and long-term side effects, posing a risk to personal and occupational safety. Objective This study aimed to test the effects of blue-enriched light-emitting glasses on sleepiness, alertness, and sustained attention during the early morning hours of night shift work. Methods To remedy the risks of reduced alertness, sustained attention, and increased sleepiness in a single-blind study design, Luminette® 3 (Lucimed SA, Wavre, Belgium) glasses emitting blue-enriched light (BL) were tested from 05:00 to 05:30 during night shift work in 21 participants at a sleep laboratory, and the effects were compared with those of glasses emitting sham dim red light (DRL). Sleepiness was rated hourly from 21:00 to 07:30 using the Karolinska Sleepiness Scale, while alertness was assessed using the PC Psychomotor Vigilance Task before and after the intervention. At the end of the night shift, sustained attention (using the computerized Mackworth Clock Test), comfort ratings, and fatigue were measured. Statistical analyses were conducted using the Friedman and Wilcoxon signed-rank tests. Results Sleepiness increased significantly throughout the night and was not significantly reduced after the intervention, with a more prolonged reduction using BL. Compared with using DRL, using BL revealed no clear benefit in terms of alertness or sustained attention, yet comfort ratings were slightly better, without any negative side effects. Conclusion In the current study, BL glasses were not clearly superior to DRL glasses in ameliorating the negative side effects of night shift work. Despite some limitations, however, this field study showed high ecological validity and demonstrated the convenient use of an intervention that is easy to implement in a realistic workplace setting.