Research shows positive effects of bright light on night shift workers

A study carried out by researchers from the University of Bergen and Haukeland University Hospital in Norway, indicates that bright light improves performance and alertness, reduces sleepiness and has the potential to lessen the risk of accidents and injuries.

The main objective of the study was to investigate how bright light, administered via standard ceiling mounted LED light sources, affected alertness and performance during simulated night shifts. Many negative health effects have been connected to night work. In addition, several different research studies have reported increased sleepiness, greater number of attention lapses and slowing of responses during night shifts, which are associated with an increased risk of accidents and injuries. 

Lighting laboratory
The study was conducted from September 2017 to February 2018 and comprised 27 participants between the age of 19-30. The participants worked three consecutive night shifts under a full-spectrum bright light (4000 Kelvin, 900 lux) and (following a four-week break) three consecutive shifts under a standard light (4000 Kelvin 90 lux). The study took place in a lighting laboratory at the University of Bergen. The lab is equipped with high quality LED luminaires and a light management system from Glamox. The light management system allows the researcher to accurately control the intensity and colour temperature of the light.
 
Testing sleepiness, vigilance and performance
Tests were conducted during each night shift assessing participants subjective sleepiness, vigilance and cognitive performance. The participants also submitted saliva samples that was used to map melatonin onset. Melatonin is a hormone that the brain releases in response to changes in light. It helps regulate the body’s internal clock, signalling that it is time to go to sleep.

Bright light can reduce the risk of accidents and injuries
The results of the tests during night shifts were all favourable for the bright light scenario. The participants were less sleepy, more vigilant and performed better on cognitive tests when they worked in the 900-lux scenario. The melatonin onset was delayed with night shifts in bright light. Thus, participants’ circadian rhythm was better aligned to a night work schedule after night work in 900 lux. The conclusion of the study is hence positive when it comes to the effects of bright light, stating “Bright light administered by ceiling mounted LED luminaires has the potential to improve adaptation to night work and reduce the risk of accidents and injuries among night workers.”

Countermeasure against sleepiness and performance deficits
The main author of the study, PhD Candidate Erlend Sunde, elaborates:  
“The study shows that ceiling mounted LED luminaires can be implemented as a countermeasure against sleepiness and performance deficits during night shifts. We think that this measure is promising also because it is non-invasive and easy to implement, as well as cost-effective. However, studies should test if similar lighting set-ups are feasible in real night work settings. Furthermore, similar light interventions need to be carefully planned for each specific situation/setting to get the desired effects”, he says. 

Further reading:
The study “Role of nocturnal light intensity on adaptation to three consecutive night shifts: a counterbalanced crossover study” is published in the renowned journal Occupational and Environmental Medicine (OCCUP ENVIRON MED): https://oem.bmj.com/content/early/2020/02/04/oemed-2019-106049

NB: Other than providing products and support for the light management system, Glamox has had no role in the study design, data collection, analysis, decision to publish or preparation of the manuscript of this study.