Circadian lighting improves sleep and performance of night shift workers

The use of circadian lighting, where artificial lighting is synchronized with a person’s natural biological rhythms or ‘body clock’, significantly improves the sleep quality and work performance of night shift workers, a major new study shows.

The Flinders University study is one of the first tightly controlled laboratory studies to simultaneously evaluate the effects of circadian light on markers of body clock timing, cognitive performance during shift work and sleep after an abrupt transition to night work.

The results of the trial led to two articles published in SLEEPfinding that strategic light exposure accelerated body clock adjustment and improved alertness and performance, as well as sleep after a night shift.

“Circadian rhythms reflect our body’s internal clocks that control the activity and timing of bodily functions, including our sleep-wake cycle,” says sleep researcher Dr. Hannah Scott from Flinders University, author of “Circadian lighting improves wakefulness, sleep and subjective sleepiness during simulated night work”, published in SLEEP.

“Shift work causes circadian disruption, for which well-timed light exposure, designed to promote alertness and facilitate circadian adjustment, is one of the most powerful methods to help adjust the body clock.”

In Australia, approximately 15% to 16% of Australian workers report working shifts. For both men and women, alternating shifts with varying schedules per week are the most common form of shift work.

The findings will be of particular importance to shift workers in enclosed environments, such as submarines, where lighting is typically dim.

“Given the complete lack of normal day-night lighting, shift work on submarines can be particularly challenging for the body clock to adapt,” says Dr. Scott.

“We wanted to explore the unique challenges that night shifts pose, particularly the disruption of the sleep-wake schedule, which can lead to reduced mental and physical performance, poorer sleep and health problems.

“We found that using circadian-informed lighting promoted better work performance and sleep for those who worked irregular hours,” says Dr. Scott.

A group of 19 adults took part in the study, which took place in the FHMRI Sleep Health laboratory under tightly controlled conditions that simulated nighttime work environments.

Participants were exposed to two different lighting scenarios over a period of eight days to compare how their body clock adapted and how they performed in a series of tasks.

The circadian lighting consisted of blue-enriched and dim, blue-poor conditions designed to help the body clock adapt to night work, while the traditional dim, blue-poor lighting simulated standard lighting conditions aboard submarines.

The research team then assessed key circadian measures, including melatonin levels and core body temperature, along with other outcomes including cognitive performance and sleep.

Importantly, during four consecutive simulated night shifts, participants’ biological clocks shifted approximately one hour faster per day than under standard lighting.

Alisha Guyett, lead author of ‘A circadian-informed lighting intervention accelerates circadian adaptation to a night work schedule in a subsea lighting environment’, also published in SLEEPsays the findings are promising for employers and night shift workers.

“The overarching benefits of circadian lighting on sleep and alertness are very clear from this study. Our findings suggest that strategic lighting interventions can likely be used to improve the performance, sleep, safety and well-being of night shift workers exposed to inadequate lighting.” light during their shift,” Guyett said.

“The circadian lighting interventions significantly accelerated participants’ adaptation to night work, which could have important implications for improving the health and performance of those who regularly work night shifts.”

Notably, after circadian lighting, participants achieved almost an hour more sleep compared to standard lighting conditions, and also reported lower levels of sleepiness during their shifts.

To test alertness, participants in both lighting conditions were subjected to the Psychomotor Vigilance Task (PVT) test, a behavioral attention measure. Those under circadian lighting conditions made half as many errors (7.4 times) as those under standard lighting (15.6 times).

Senior Flinders Health and Medical Research Institute: Sleep health researcher Professor Peter Catcheside says: “This study highlights the importance of the circadian system and circadian friendly lighting to help alleviate some of the significant challenges of shift work.

“It adds to what we already know about using these interventions to help optimize workspaces for better performance, safety and wellbeing in the modern workforce.

“These findings have important implications for the lighting conditions of submarines, as well as for mining and other workplace environments where lighting conditions can make it more difficult for shift workers to successfully adjust their biological clocks to match the work schedule,” he adds.