Circadian Rhythms Influence Immunity, Study Shows
It's common knowledge that too little sleep can increase our odds of getting sick, but a new study sheds light on just how direct the connection is. Researchers found that the body's circadian clock controls an essential immune system gene in mice -- a gene that helps the body ward off bacteria and viruses.
"People intuitively know that when their sleep patterns are disturbed, they are more likely to get sick," study author Erol Fikrig, professor of epidemiology at the Yale School of Medicine, said in a press release. "It does appear that disruptions of the circadian clock influence our susceptibility to pathogens."
Circadian rhythms are internal oscillations that follow an approximately 24-hour cycle and regulate various physiological and mental processes. The rhythms are controlled by a particular group of nerve cells in the brain and can be influenced by behavior.
"They are the reason we feel hungry, sleepy, more alert and have better mental clarity at consistent times every day and night," explained Rebecca Scott, a sleep specialist at the New York Sleep Institute, who was not associated with the study.
"And those are just some of what we perceive," she continued. "Our blood pressure, hormones, immune function and a host of other functions also follow a circadian rhythm."
In the new study, researchers set out to further unpack the connection between immunity and the body's clock by examining whether a key immune system gene -- the so-called "Toll-like receptor 9" gene -- is under circadian control and, if so, what that might mean for immune system function, including defense against infection.
Using mice, the researchers found that when levels of that particular gene were highest, the mice were better able to withstand infections. The results were published online Wednesday in the journal Immunity.
"What we discovered is that this innate immune gene is under circadian rhythm," Adam C. Silver, a postdoctorate associate in infectious diseases at Yale and one of the study's authors, told The Huffington Post.
"We also found that the time of vaccination influenced the immune response," he added.
Indeed, the study suggests that when expression levels of that same gene were highest, the mice had the greatest response to vaccination. Though Silver cautioned that the new research is preliminary and merely a building block in a relatively new area of scientific exploration, the potential implications are rather novel, suggesting that getting vaccinated at certain points in the day might dramatically impact the immune system's ability to fight off certain sicknesses.
"If we have a better understanding of how specific immune markers are affected or changed by disruptions in our circadian rhythm, then we may be better able to advise the public on how to potentially ward off sickness, especially when they might be more vulnerable to a cold, flu or virus," Scott agreed.
In the meantime, as such research continues, there are steps people can take to help maintain their circadian clock.
Certain rhythms, such as the sleep-wake cycle, are directly influenced by behavior, Scott explained. That means being exposed to too much light before bed or not getting enough light within an hour of waking can impact one's biological or inherent clock.
"Keep in mind that we feel, function and are healthiest when we work with our circadian rhythms and keep them in-line with the 24-hour day," Scott said. "Establishing routines with eating, sleeping and exercising as best as possible maintains our rhythm and encourages health -- emotional and physical."