Almost everyone follows an internal bodily clock, or circadian rhythm. This clock controls when a person feels sleepy, awake, hungry, etc.
Light is a strong influence on circadian rhythms. Daylight prompts the brain to produce hormones like cortisol to wake the body up. As night falls, the pineal gland produces melatonin, which makes a person feel sleepy.
People who work the night shift can experience disruptions in their brain’s internal clock. This can affect sleep, mood, and physical well-being. Some develop shift work disorder, which undermines the quality of sleep. The condition can cause:
If someone could fully realign their internal clock to a night shift, they would likely see improved health. While total adaptation is rare, new research published in The Journal of Physiology shows a potential means to reach it. According to the study, changing light exposure to match a night shift schedule can affect people’s circadian rhythms.
Shifting Light-Dark Cycles in Shift Workers
The study recruited 21 nursing and medical staff members working at an intensive care unit (ICU). Researchers measured recruits’ circadian rhythms by recording the melatonin levels in their urine. The study measured participants’ light exposure using wrist actigraphs.
Researchers first collected data from recruits as they worked a series of day shifts (or had days off). Then, recruits took three to four night shifts in a row. The researchers then looked at how participants’ internal clocks reacted to the transition.
The timing of light exposure was the most significant predictor of how participants’ bodies responded. In fact, 71% of the differences among recruits were due to light exposure. These results suggest altering someone’s pattern of light exposure might help them adapt to night shifts. For instance, more light at night could help a person sleep during the day and remain awake at night.
However, researchers caution that a one-size-fits-all approach will likely be ineffective. The effects of light exposure depended on a person’s internal clock rather than specific time of day. In other words, “morning” and “evening” people may need different interventions.
- Melatonin and sleep. (n.d.) National Sleep Foundation. Retrieved from https://sleepfoundation.org/sleep-topics/melatonin-and-sleep
- Moving light-dark exposure could reduce disruption faced by night shift workers. (2018, March 27). ScienceDaily. Retrieved from https://www.sciencedaily.com/releases/2018/03/180327203014.htm
- Shift work disorder. (n.d.). National Sleep Foundation. Retrieved from https://sleepfoundation.org/shift-work/content/shift-work-disorder-%E2%80%93-symptoms
- Stone, J. E., Sletten, T. L., Magee, M., Ganesan, S., Mulhall, M. D., Collins, A., . . . Rajaratnam, S. M. (2018). Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: Role of light-dark exposure. The Journal of Physiology. Retrieved from https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/JP275589
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