Circadian-informed lighting, where artificial lighting is synchronised to a person's body clock, significantly improves sleep quality and work performance for night shift workers, an Adelaide sleep trial has found.
The Flinders University trial evaluated circadian-lighting effects on markers of body-clock timing, work-shift cognitive performance, and sleep following an abrupt transition to night shift work.
Two papers on the study have been published in the prestigious Oxford University Press SLEEP journal, finding that strategic exposure to light accelerated body-clock adjustment and improved alertness and performance, as well as sleep after a night shift.
"Shift work causes circadian disruption, for which well-timed light exposure, designed to promote alertness and facilitate circadian adjustment, is one of the most potent methods to help retime the body clock," said Flinders University sleep researcher Dr Hannah Scott.
In Australia, about 15-16 per cent of workers report being shift workers, and rotating shifts with varying weekly schedules are the most prevalent type.
"We wanted to explore the unique challenges posed by night shifts, particularly the disruption to sleep-wake schedules, which can lead to impaired mental and physical performance, poorer sleep and health issues," Dr Scott said.
"We found that the use of circadian-informed lighting promoted better improved job performance and sleep for those working irregular hours."
Nineteen adults participated in the study at Flinders Health and Medical Research Institute under conditions that simulated night work environments.
Participants were exposed to two lighting scenarios for eight days to compare how their body clock adjusted and how they performed in a series of tasks.
The circadian-informed lighting consisted of blue-enriched and dim, blue-depleted conditions to help the body clock adjust to night work, whilst the traditional dim, blue-depleted lighting simulated the standard lighting conditions onboard submarines.
Shift work on submarines is particularly challenging for the body clock because of the complete lack of normal day-night lighting.
The research team assessed circadian measures including melatonin levels and core body temperature, along with other outcomes including cognitive performance and sleep.
Over four consecutive simulated night shifts, the circadian-informed lighting shifted participants' body-clocks around one hour faster per day compared to the standard lighting.
After circadian-informed lighting, participants also had almost one hour more of sleep compared to the standard lighting condition as well as reporting lower levels of sleepiness during their shifts.
