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Bifurcated Sleep Patterns: What Are They & How Do They Have the Potential to Help Shift Workers?

In the current state of the world, the health of shift workers has become more essential than ever. Janitorial staff, health workers, and many other essential workers are all shift workers that might work around the clock, 7 days a week. As such, a significant amount of research has been conducted to determine the potential risks of disrupting someone’s sleep patterns for prolonged periods of time, which is the reality that many shift workers experience. One such study was overseen by Claire C. Caruso at the National Institute for Occupational Safety and Health, and it revealed that shift workers are at increased risk for impaired job performance, as well as negative health outcomes like obesity and a wide range of chronic diseases. This study supports the vast impact of altered sleep patterns on people’s overall health, and as a result, it has recently become a focus point in circadian research known as bifurcated sleep patterns.

One of the many goals of studying circadian rhythms is to learn more about the human body’s internal clock and how it is responsible for coordinating many biological processes. But the most notorious point of study is the regulation of sleep patterns. This is important because the process of adjusting a circadian clock to a new schedule usually takes a couple days. This is commonly known as “jetlag”, and it can be applied to shift workers as well. The danger with shift work lies with this “jetlag”. The problem is that by operating at a time of night that one’s body expects to be asleep, a shift worker cannot function efficiently, which results in negative outcomes, such as those found by Caruso. So, what if people could speed up their adjustment to the “jetlag?" This is where bifurcation comes into play.

Bifurcation, in terms of circadian rhythms, simply means that the 24 hour day is splitting the day into shorter sleep-wake patterns. Instead of having one period of activity and one period of rest in a single day, bifurcated sleep cycles have 2 alternating periods of activity and rest in a single day, potentially allowing quick recovery from the “jetlag” that one would normally get from interfering with their regular circadian rhythm. Researchers such as Jonathan Son, Deborah A. M. Joye, Andrew H. Farkas and Micheal R. Gorman at the Department of Psychology and Center for Circadian Biology at UCSD have demonstrated this pattern and the requirements for it in male mice models. Their study found that dim light at night was crucial to establishing a bifurcated sleep pattern in mice and that they adjusted the most consistently to 2 cycles of 8 hours of light followed by 4 hours of dim light. It’s no surprise that lighting is a crucial part of circadian rhythms because the light we take in from our surroundings can shift circadian rhythms to match what the environment is perceived to be.

The potential applications of a bifurcated sleep pattern in humans are vast, but shift workers have the most to gain. Although simply taking a nap can mimic the behavior of bifurcated sleep patterns, it is not considered to truly be bifurcation because the endogenous, circadian clock is not adjusted. An article by Elizabeth M. Harrison and Michael R. Gorman of the Department of Psychology, Center for Chronobiology at UCSD highlights that the biggest challenge for shift workers is training their clock to be active at night when light signals that they receive from the sun during the day tell them that it is time to be awake. This is in addition to the social demands during the day after a long night of work. Unfortunately, it is currently difficult to replicate bifurcation in humans outside of very strict experimental conditions. This makes the concept, at this time, difficult to fully apply, but there is still more work to be done and knowledge to discover about the potential flexibility of our circadian rhythms and how we can adapt them to better the health of shift workers everywhere.