There’s a master clock inside your head. Tucked deep inside your brain, this expert timekeeper keeps all of the cells in your body running smoothly, protects you from chronic disease, and helps you have deep, rejuvenating sleep. To keep these systems ticking along, this internal clock relies on a steady diet of healthy habits and mindful routines.
Unfortunately, steadiness and routine can be hard to come by, especially since overload and uncertainty seem to be the hallmarks of 2020. Many of us are navigating strained relationships due to lack of physical proximity (or political proximity), souped-up tech algorithms leading us down information rabbit holes, and a generalized din of dread caused by the pandemic.
In today’s culture of disruption, it’s even more important that we create daily habits that support our well-being so we can get rejuvenating sleep and allow our minds to remain receptive and open
In the best of times, stress can interrupt our sleep patterns and cause us to lose hold of the daily habits and rhythms that keep us healthy. In today’s culture of disruption, it’s even more important that we create daily habits that support our well-being so we can get rejuvenating sleep and allow our minds to remain receptive and open in order to meet the unique challenges of the COVID era.
What is Circadian Rhythm?
What most of us may not realize is how nearly all of our cells, tissues, and organs rely on internal daily rhythms, or circadian clocks, to keep our bodies running smoothly and in peak health under the watchful eye of the master clock. And those internal daily clocks rely on routines and timing in order to keep ticking for our optimal health.
The master clock is headquartered in the suprachiasmatic nuclei (SCN) in the brain’s hypothalamus. There are peripheral clocks located all over the body—in the heart, lungs, kidneys, pancreas—and they are synchronized with the master clock through both hormonal and neuronal signals. These clocks make up our circadian system, which controls the functioning of each bodily process, including sleep, metabolism, hormone release, alertness, blood pressure, heart function, cognitive function, and the immune and reproductive systems. Take a moment to read that list again. Together, the circadian rhythms synchronize most of our brain and body functions. “The master clock in the brain is the conductor of the orchestra. The other clocks are the ‘players’ fine-tuning local timing under the guidance of the SCN clock,” explained Dr. Steven Lockley, an associate professor of medicine at Harvard Medical School. In order for our bodies to be in peak health, timing, rhythm, and habit are key. “We need to do things at the right time; for example, eating in the day when our metabolic efficiency is optimal, and not at night when the brain is promoting sleep and fasting.”
As humans, we evolved to follow regular patterns of light-dark exposure—we need the sun’s blue-enriched light during the day for alertness and activity, and the dark to prime our sleep, recovery, and repair mode. “The key to healthy sleep and circadian rhythms is stable, regularly timed daily light and dark exposure,” said Lockley. “These daily time cues are needed to reset our circadian clocks each and every day, which will not only determine how well we sleep but our very cellular health.”
What connects our internal, circadian rhythms with the outside world is the light that enters through our eyes. The light—the strongest synchronizing agent—stimulates a neural pathway to the “master clock,” which signals other brain regions and the peripheral clocks in the body that control hormones, body temperature, and other physiological processes that help regulate when we feel sleepy or awake.
Healthy circadian rhythms rely on regularity and stability— for the timing of light, timing of exercise, and timing of meals.
“Light is free for most of us, and you don’t even have to go outside to get it,” said Dr. Phyllis Zee, professor of neurology and the director of the Center for Circadian and Sleep Medicine at Northwestern University. Dr. Zee was one of the authors of a recent study that showed office workers who had exposure to light through a window tended to have longer sleep duration, better sleep quality, greater physical activity, enhanced mood, and better quality of life compared to office workers with less light exposure.
Ultimately, healthy circadian rhythms rely on regularity and stability— for the timing of light, timing of exercise, and timing of meals. “This is so your body’s physiology can anticipate what you’re going to do, and be prepared rather than reactionary,” said Dr. Zee. If you exercise too close to bedtime, for example, it can delay the timing of your rhythms, making it more difficult to fall asleep. Similarly, your blood pressure rises before you wake up in the morning, so if you get up at 2:00 in the morning, you’re more likely to feel more unstable because your blood pressure didn’t anticipate your need to get up. “The circadian system is the top dog, and regulates all of these systems, including sleep,” she said.
How Circadian Rhythms Impact Our Health
In today’s world, disruptions in circadian rhythms are common, especially when we are overloaded and operating in “react” mode rather than mindfully making choices about our behavior. “We override our natural rhythms by staying up late, using electric light, and eating any time of night, more than we think,” said Dr. Lockley. If you live in New York, for example, and stay awake two hours later than normal, it’s as if you’ve traveled two time zones west. Add a third hour on the weekend, and when you wake up on Monday morning, you have what’s called “social jet lag,” because your body clock is set to California time even though you never went anywhere. “The more frequent the flip-flopping between light and dark, the more problems you will have with social jet lag and imperfect synchronization with the outside world,” said Lockley. “Stability is key.”
When frequent sleep disturbances, night-time screen use, or high caffeine intake throw our light exposure out of whack, the natural circadian rhythms of the body are reset—to either speed up or slow down the internal clock, which influences all the systems that it controls. Extreme circadian instability—as seen with shift workers, such as nurses, doctors, transportation and factory workers, and first responders—can cause a variety of chronic health problems, increasing the risk of cardiovascular disease, impaired immune function, high blood pressure, diabetes, obesity, depression, and some forms of cancer.
Extreme circadian instability—as seen with shift workers, such as nurses, doctors, transportation and factory workers, and first responders—can cause a variety of chronic health problems.
Most of the research on circadian disruption and health comes from looking at shift workers, who typically work out of phase with their internal clocks— which can be off by as many as 12 hours. It is the continuing misalignment of their behavior from the clock, such as sleeping and eating at the wrong time, that leads them to develop health problems. “Shift workers adapt a little to the night shift, but not fully, and then they adapt back to the day shift, but not fully, and this lack of stability affects cell processes, metabolism, hormone levels, and many other systems and causes of chronic disease,” said Dr. Lockley.
A few helpful suggestions include: minimizing the number of night shifts in a row, keeping the same sleep-wake schedule on your at-home days as on your work days, if possible; getting out into the sun once you wake up, which will cue your biological clock that it’s time to be alert; and staying away from alcohol as a sleep aid, which may appear to calm the brain to help fall asleep, but will di