What is the circadian rhythm & 3 tips to keep it in check

Circadian rhythms are 24-hour cycles that regulate bodily processes like energy levels, hunger, mood, body temperature and sleep. Depending on your age, gender and specific hormonal makeup—as well as a host of environmental factors—your circadian rhythm might look different from someone else’s.

Let’s dive into the inner workings of circadian rhythm, what factors can affect it, and how to take care of your internal clock for optimal wellbeing.

What is the circadian rhythm?

The circadian rhythm is a 24-hour cycle regulated by your body’s internal clock.¹ The word circadian comes from the Latin circa diem, which means “about a day.” Many organisms (not just humans) rely on this internal biological clock to function and survive. The circadian rhythm runs on a daily schedule set by your internal clock, essentially run by molecules interacting with cells.¹
A “master clock” in your brain keeps your circadian rhythm and internal clock properly synced.¹ When your internal clock is running on time, your circadian rhythm and its associated bodily processes are also running smoothly. When the two are out of sync, it can cause issues, including with your sleep cycle.

Keep reading to learn more about the circadian rhythm and how it affects your sleep-wake cycle.

How does the circadian rhythm work?

The circadian rhythm controls various bodily systems, including digestive processes, energy levels during waking hours, and body temperature regulation. But one of the primary systems affected—and the one you may have heard the most about regarding the circadian rhythm—is the sleep-wake cycle. As you sleep, your body experiences several rounds of the sleep cycle and during each one, your body goes through four different phases.²

Stage 1 is the NREM (non-rapid eye movement) phase, which only lasts about five minutes or less. During this phase, it’s easy for you to wake up.

Stage 2 happens within the first hour of sleep. It’s still a light sleep, but your brain wave activity starts to slow during this phase.

Stage 3 is also called Slow-Wave Sleep (SWS) or Delta Sleep, and it’s more difficult for someone to wake you up during this stage. In Delta Sleep, your immune function is at its highest, with your body growing and making any necessary repairs.

Stage 4is the deepest phase of the sleep cycle, also known as REM (rapid eye movement) sleep. This phase is when your brain waves are reactivated to process, store, and discard information. REM sleep is when the most vivid dreaming occurs, and your brain forms long-term memories.²

This entire sleep cycle typically lasts about 90 minutes. Ideally, your body will go through four to six of these as you sleep to feel rested, resulting in the recommended seven to nine hours of sleep per night.³

A disrupted circadian rhythm can throw off this sleep-wake cycle by waking your body up during a sleep cycle or making it difficult for you to fall asleep or wake up when needed. This happens primarily in response to the timing of light exposure. However, other factors can affect your circadian rhythm—and therefore sleep—too.

What disrupts the circadian rhythm?

Your body keeps its circadian rhythm without your intervention, but if your internal clock happens to be disrupted, the optimal functioning of your bodily processes can be affected.

What can that look like? Trouble sleeping, low energy levels, mood swings, and more. Here are some factors that can affect your circadian rhythm.

Shift work

Exposure to light plays a big role in circadian rhythm function. As humans, we’ve evolved to associate daylight with alertness and darkness with rest. Even our eyes have not developed the ability to process incoming information in the dark—meaning we can’t see as well at night.¹

This isn’t necessarily a problem if your schedule requires you to be awake during the day and asleep at night. But if you work the night shift or non-traditional hours, your sleep-wake cycle—your circadian rhythm—will be disrupted.

Artificial lighting

Working in artificial and fluorescent lighting before sunrise or past sunset can have the same effect. And, unfortunately, cell phones—the devices that so many of us are never without—can also produce a blue light that throws off your circadian rhythm. This means that even after the world goes dark, screens like phones, tablets, laptops, and televisions keep our brains “on.” Many people attempt to fall asleep using their devices, which can confuse the master clock’s interpretation of when it’s time for us to be awake versus asleep.¹

Jet lag

Jet lag from travel is another common disruption for the circadian rhythm.¹ Similarly to the simplicity of pre-tech days, crossing multiple time zones in a short time wasn’t an issue for our ancestors. They traveled over more extended periods, allowing their bodies to “catch up.”Modern air travel makes it easier to cross time zones quickly. Long, intercontinental flights can greatly impact the circadian rhythm. The change in light exposure and sleep-wake schedule can throw off the 24-hour internal clock until the person becomes acclimated to the new environment.¹ Then, they often need to reacclimatize upon their return, causing further disruption to their circadian rhythm.

Can smartwatches track my circadian rhythm?

Now that you know the ins and outs of the circadian rhythm, how can you monitor yours? Smartwatches are one way people keep an eye on the amount of sleep they get each night, as well as the quality of sleep they get. Smartwatches can provide a valuable insight for those interested in improving their sleep. By wearing a smartwatch on your wrist each night (or a similar type of device), you can learn a lot about the quantity and quality of your sleep.

These sleep tracking devices use motion detectors called accelerometers to measure movements, and heart rate monitors to record how your heart rate fluctuates while you sleep. Some may also include a microphone to detect sound—like a pet waking you up or your own snoring.⁴

In the morning, either on the device itself or via an external app, you can look at the analytics on the quantity and quality of your sleep, noting when you were most restless, when you slept deeply, and how many hours of sleep you got. This can be incredibly helpful for anyone dealing with sleep-related issues.

3 tips to help you reset your circadian rhythm

Anything else you should know about the circadian rhythm? Yes, in fact. Here are two final items to note.

1. Your circadian rhythm may be responsible for your afternoon slump.You’re not imagining it: the afternoon slump—those feelings of fatigue and fogginess—are usually caused by the daily patterns of your circadian rhythm. They don’t happen at the exact same time for every person, although an afternoon dip in energy level is a normal part of a healthy, functioning circadian rhythm.¹

2. Your circadian rhythm may be affected by what you drink and when.Caffeine and alcohol may affect your circadian rhythm and therefore your sleep. Alcohol can affect melatonin production⁵, and caffeine can actually reset the body’s circadian rhythm altogether.⁶ If you’re trying to maintain a healthy circadian rhythm, it’s good to watch your intake of both alcohol and caffeine, and specifically stop drinking coffee or caffeinated drinks after 2 p.m.

*These statements have not been evaluated by the U.S. Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.