What is Circadian Rhythm?

You’ve no doubt heard the term before, but what is circadian rhythm and what does it mean for your sleeping habits?

Every living organism—from you down to that house plant in your kitchen you’re desperately trying to sustain—has a circadian rhythm. This can sometimes get conflated with our biological clocks, but the two vary slightly. The circadian rhythm definition is an easy one to remember: it is the physical, mental, and behavioral pattern we follow on a daily cycle. Cycles vary from one being to another, but they are almost always somewhere around 24 hour time periods.

Having a circadian rhythm in balance with your needs allows you to get the right amount of sleep at the right times, and while there’s a lot of ins and outs with what keeps us up and down, knowing the basics can have a huge impact on your life.

What is the difference between circadian rhythm vs. biological clock? Biological clocks as a concept can feel mythological, but we really do abide by certain timing thanks to our biology—in fact, biological clocks are what create circadian rhythms. They are made up of specific proteins and are found in every tissue and organ of the body, driving our cells and internal timing to follow a certain path.

There’s even a master clock that controls all of the biological clocks of a living thing. The master clock is made up of over 20,000 neurons and is called the suprachiasmatic nucleus, or SCN. The SCN is located in the hypothalamus and receives direct stimulation from what we’re seeing—which is why light and time of day plays such a role in our daily habits.

How does circadian rhythm work? Sensory input (Like light!) from our environments can change the molecular structure of our biological clocks—this makes sense when you compare the daily doings of diurnal creatures like humans and nocturnal creatures like owls.

External cues like lighting are called “zeitgebers” and they function to help reset our internal clocks throughout the cycle. This light-dark cycle is responsible for synthesizing and releasing melatonin—which is the hormone that keeps your circadian rhythm rolling. This hormone regulates other biological processes as well, depending on whether an animal is nocturnal or diurnal.

All of these external cues and internal processes work together to ensure that we maintain healthy sleep-wake cycles and help to regulate our body temperatures, which we know can impact the quality of our sleep.

What other factors impact our circadian rhythm? One study has found that keeping a regular routine during the day can help enhance circadian rhythms, especially in seniors who struggle with sleep. Simple behavioral therapy might be the key to helping those who struggle to sleep. How can you improve circadian rhythm now?

  • Eat consistently Establishing a regular rhythm to how you eat, what you eat, and when you eat may help to keep your circadian rhythm on a regular cadence. Meal timing in species in the wild is on a pretty regular clock—hunger strikes around the same time. Eating at regular intervals consistently day in and day out can help regulate your hormone production.
  • Eat more protein High-carb diets are newer to our species and some researchers have observedthat people who opt for more protein throughout their day sleep better than those who reach for the cinnamon rolls in the morning and cake after dinner.
  • Bask in those cooler temperatures Sleeping cool is a great way to get better sleep, we know that. Cooler nights and warmer days are perfect external cues to tell our circadian rhythms that things are going along swimmingly. In the same way that our light-dark cycles play a huge role in our circadian rhythm, body temperature helps regulate these processes and also plays a part in the quality of your sleep. Doing activities to raise your body temperature before heading to bed can throw your internal rhythm off and make it harder to get deep sleep. Cooling down before bed should be a part of everyone’s nighttime routine.

What is circadian rhythm disorder? Circadian rhythm sleep disorder can come in a few different forms. These disorders typically live in two categories—intrinsic and extrinsic. Intrinsic disorders are patterns that are natural, and stem from internal causes. Perhaps you just happen to wake up earlier than the “normal” person, or you sleep is irregular day to day. Extrinsic disorders are circumstantial and can happen if you work a later shift, travel to a new time zone, or have odd times to rest during the day due to a hectic schedule.

Delayed Sleep Phase Syndrome (DSPS) and Advanced Sleep Phase Syndrome (ASPS) refer to disorders that impact when people feel tired—those with DSPS are night owls who stay up much later, and ASPS are early to bed and early to rise. Irregular Sleep-Wake Rhythm is found in people who rest at random throughout the day and don’t sleep for longer periods like the average person does. Usually they take naps that add up to between 7-9 hours a day. Non-24-Hour Sleep-Wake Syndrome occurs when sleepers have slightly longer internal clocks that cause them to go to sleep much later than typical every few days. This often occurs in blind people, because their light-dark cues aren’t stimulating the SCN.

Extrinsic disorders develop when your environment causes unusual changes to your schedule it can conflict with your circadian rhythm. Working third shift, for example, can cause some people to struggle sleeping during the day and wake up ready for work at night. While some shift workers have no problem adapting, those who do may be suffering from Shift-Work Sleep Disorder. Working rotating schedules can have a higher chance at losing out on sleep, since your internal clock can’t regulate. Jet Lag is a huge factor in your circadian rhythm that you might not realize is actually a disorder. Traveling to a new time zone can have you all sorts of mixed up, and generally takes a few days to adjust to.

Treatment for circadian rhythm sleep disorders There are a few different therapies out there that can help with these sleep disorders. Behavioral therapy—such as maintaining a regular sleep-wake cycle and sticking to a consistent bedtime routine—can make a huge difference in your internal timing systems. Avoiding caffeine, naps, and nicotine can also help keep your internal clocks running smoothly. Regular exercise can also help keep things in check, but make sure not to workout immediately before bed, your core temperature could prohibit your best sleep.

Light therapy can also help. Correcting light-dark cycles by using a bright light box has been effective in those with Delayed Sleep Phase Syndrome and Advanced Sleep Phase Syndrome. Keeping bright lights near you at the appropriate times of day can make a huge impact. Medications are also available to help, as are over-the-counter melatonin supplements. If you think you might have a circadian rhythm disorder, your doctor should be able to help you find a diagnosis and treatment.

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Shelly Weaver-Cather
Shelly Weaver-Cather

Shelly Weaver is part of the Content Team at Tuft & Needle, leading the writing and editing of our blog. Not quite a Phoenix native, (They take that sort of thing super seriously.) Shelly has spent most of her life in the Phoenix Metro area and has no plans of leaving anytime soon. She made the unexpected jump out of wedding photography and onto T&N’s team in 2016, and found a passion for the people that keep the lights on. She still finds herself shooting in her free time, though these days there are less bridal portraits and more masterpieces of her first child, Duke, a lab-pit mix with an unparalleled love for both T&N mattress hogging and couch destroying.

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