The phrase “circadian rhythm” seems to appear with increasing frequency in the news. The study of circadian rhythm also got a boost when the 2017 Nobel Prize in Physiology or Medicine was awarded to three pioneering researchers in this area. But many people may not understand what it means and why it’s important.
All biological processes that occur with a natural cycle of about 24 hours are said to have a circadian rhythm. This cycle—which occurs even in the absence of light—takes place within almost all organisms. It has evolved to make sure that different physiological processes happen at the right time of day to keep us healthy. Some of these include normal fluctuations at night of blood pressure, stress hormones and hormones that control hunger.
In a small region of the brain, humans have a master clock called the suprachiasmatic nucleus (SCN). The SCN is sensitive to light and contains specialized “clock genes” to help keep the body on a 24-hour schedule. The SCN also plays an important role in sleep/wake patterns by controlling the release of the hormone melatonin, which helps us feel tired at night.
These clock genes are not only present in the SCN but also in every cell in the body, including the heart, liver, muscles, kidneys and other vital organs. Like an orchestra conductor, the SCN is responsible for making sure all of the molecular clocks are in sync, both with each other and the natural light/dark phases of day and night.
More and more studies relate disruptions in circadian rhythm with the development of chronic diseases such as cancer, diabetes, heart disease, depression and obesity. Working at night (shift work), jet lag and spending more time in front of the television, computer, tablet or smartphone can all contribute to this kind of disruption, called circadian rhythm disorder. Poor quality sleep from conditions such as sleep apnea or simply not getting enough rest can make the problem worse. A recent study reported that only 10 percent of people in the U.S. prioritize sleep over other activities.
Because when and what we eat may also change our circadian rhythms, eating at the right time of day can keep our circadian rhythms flowing smoothly. To help keep your circadian clock running on time, try to keep a regular routine for eating and sleeping every day—even on weekends. Aim to get around seven to eight hours of sleep a night and avoid light late in the evening, especially the blue light from electronic devices.
Understanding the importance of circadian rhythms and working with, not against, these natural cycles may be the first step in optimizing our health.
John Chatham, DPhil, FAPS, is a professor of pathology in the Division of Molecular and Cellular Pathology at the University of Alabama at Birmingham.
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