Study reveals time of sleep, not just quantity, is important

The timing of one’s sleep can be just as vital as the amount or number of hours acquired, a study in Washington State University, or WSU, claims. To determine the effects of the sleeping-waking cycle, researchers from the WSU’s Department of Integrative Physiology and Neuroscience experimented on mice, which share a similar body clock with humans.

In changing the mice’s usual cycle of sleeping and waking, it was discovered that while they got enough sleep, it was of poorer quality, according to Ilia Karatsoreos, an assistant professor in WSU. The shift also affected the animals’ immune response, making them more susceptible to illness. “This represents a very clear dysregulation of the system. The system is not responding in the optimal manner,” Karatsoreos said.

Over time, according to Karatsoreos, this could have serious consequences for an organism's health. “Just like you have a car that you're running into the ground -- things don't work right but you keep driving it until it stops. That's what could happen if you think of disruption going on for years for somebody who's working shift work,” he added.

Most studies on sleep zeroes in on the homeostatic process to determine the effects of sleep deprivation or the overall amount of sleep one needs. The research done by Karatsoreos and his colleagues, meanwhile, presents a unique look into the circadian process, a brain-driven clock that controls the rhythms of various biological processes, from digestion to blood pressure, heart rate to waking and sleeping. This cycle is found in most everything that lives more than 24 hours, such as plants and single-celled organisms.

This research, published in the journal Brain, Behavior and Immunity, poses significant implications for modern living, said Karatsoreos and his co-authors. Citing that “disruption of the circadian clock is nearly ubiquitous in our modern society,” the study listed factors such as nighttime lighting, shift work, jet lag and even the blue-tinged light emitted by cell phones and tablets.

In the experiment, researchers used mice whose body clocks run at about 24 hours. Upon housing them in a shorter 20-hour day, their biological clocks were forced to be out of sync with the light-dark cycle. After four weeks, the researchers injected the mice with lipopolysaccharide, a molecule found in bacteria that can make an animal sick without being contagious.

While the mice on the 20-hour cycle were getting the same amount of sleep as they did on the 24-hour cycle, researchers discovered the sleep they were getting was not as good. The authors noted that the mice woke more often, with the pattern of their brains’ electrical activity related to restorative sleep was greatly reduced. This resulted to a blunted immune response, leaving the mice potentially less able to fight illness and more likely to get sick.

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