Circadian Rhythm 101: Everything You Need to Know to Sleep Better

2.18.2025 0 comments

Author: Trisha Houghton, CNS, ASIST

Do you find yourself struggling to fall asleep or wake up frequently throughout the night? 

If so, your circadian rhythm may be off! 

Sleep isn’t just something that happens; it’s a carefully regulated function that our body uses for so many things—from organizing thoughts and processing information to restoring damaged cells.  

The “sleep-wake” cycle is incredibly delicate and can easily be thrown off, leading to sleep problems. In this post, we’ll take a deep look at what the circadian rhythm is, how it regulates sleep, and what happens to alter or change it.  

But don’t worry—at the end, we’ll also share simple, practical solutions that will help you restore a naturally balanced circadian rhythm so you can start sleeping better. 

Circadian Rhythm 101: A Closer Look 

What is the Circadian Rhythm?  

The circadian rhythm is the name scientists have given the “24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment [1].” 

Or, put another way, it’s your “body clock”. It tells your body when to wake up and when to go to sleep, and in so doing, affects other internal systems—like your hormone production and digestive system—by up- or down-regulating them. 

Your brain controls the circadian rhythm in your body, making sure that your body is at optimal function—whether that function is working, playing, or sleeping—all day and night long.  

How Does the Circadian Rhythm Work? 

The circadian rhythm is tied to the suprachiasmatic nucleus (or SCN) cells in your hypothalamus [2]. These cells are incredibly photosensitive, and the “clock genes” inside the SCN respond to an increase or decrease in light. 

When you are exposed to more light (during the day), the SCN sends signals to your body that it’s time to increase energy production, digestion, hormone production, and so on. When light decreases or vanishes altogether (with the setting of the sun and falling of night), the signals tell your body it’s time to raise your body temperature, diminish energy production, and start shutting down internal processes so you can sleep. 

What Affects My Circadian Rhythm? 

No surprise, the thing that has the greatest impact on your circadian rhythms is light exposure. 

During the day, your brain is telling your body to fire on all cylinders—and it’s doing so because of the light’s effects on your SCN cells. When the light fades with sunset and night, it shuts you down. The natural light cycle of day and night has regulated our circadian rhythms for as long as mankind has existed. 

But modern technology—aka, artificial lights—can seriously impact your sleep cycle by increasing the amount of light you’re exposed to during the day and night. Even if your body begins to respond to the decreasing environmental light once the sun starts to set, exposure to bright artificial light—such as inside offices, restaurants, your home, etc.—can signal to your brain that it’s not yet time to shut down. That means you stay awake for hours after your circadian rhythm would have shut down otherwise. 

Light is the biggest factor that affects your circadian rhythm, but not the ONLY factor. There are other things that can throw off your natural sleep-wake cycle, including [3]: 

• Poor sleep habits. If you don’t keep a regular sleep schedule, but alternate your sleep/wake pattern every day, it can impact your circadian rhythm significantly. 

• The timing and quantity of meals/food intake. Eating too much and/or too late at night is a signal to your brain that your body isn’t ready to shut down. Late-night meals (even large snacks) can cause you to stay awake long after your body should have shut down. 

• The timing and intensity of exercise/physical activity. Work out too late in the evening, and your activity will tell your brain it’s not yet time to sleep.  

• Stress and anxiety can both throw off everything from hormonal balance to energy production to neurochemical production, leading to impaired sleep. 

• Overnight travel and/or work shifts. Working or staying awake late into the night/overnight and sleeping during the day can seriously impact your circadian rhythm. Shift workers, nurses, truckers, and others who stay awake all night often experience sleep problems for this very reason. 

• Medications may cause you to sleep less or more. Sleeping more can impact your circadian rhythms nearly as much as sleeping less does.   

• Mental health conditions, or conditions involving injury to your head or brain can also impair your natural sleep/wake cycle. 

• Hormonal changes. Research [4] has shown that (especially among men) changes to hormone levels (particularly steroid hormones like cortisol, estradiol, and testosterone) can have a significant impact on your circadian rhythms. This is one reason why so many aging men and women experience sleep troubles.  

The Consequences of an Altered Circadian Rhythm  

What happens if your circadian rhythm is impaired or thrown off? You might experience:  

• Sleep problems, such as insomnia, restlessness, and more frequently waking up through the night. 

• Fatigue, typically caused by lack of sufficient restful sleep. 

• Concentration troubles, because your tired brain can’t summon enough energy to concentrate (especially after a long day of work). 

• Excessive sleepiness and drowsiness, possibly even falling asleep in the middle of the day (such as at the wheel of your car!). 

• Cognitive performance issues, such as decreased memory, difficulty focusing, and struggles with high-precision tasks. 

• Health problems, such as higher risk of heart attacks, diabetes, high blood pressure, obesity, and even cancer.  

• Slower wound healing and post-workout muscle recovery. So much cellular regeneration and repair takes place while you sleep.  

• Hormone and neurochemical fluctuations, leading to hormonal imbalances and a higher risk of depression, anxiety, and other mental health disorders. 

• Digestion issues, due to impaired digestive function.  

All this sounds pretty bad, doesn’t it? 

The good news is that an altered/impaired circadian rhythm isn’t a PERMANENT problem—it’s one you can fix surprisingly easily.  

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How Can I Improve My Circadian Rhythm and Sleep Better? 

Improving your circadian rhythm is simply a matter of time, discipline, and commitment to a few simple actions: 

1. Following a regular sleep schedule. Going to sleep and waking up at the same time every day (yes, even on weekends!) allows your body to fall into the proper “rhythm”. (Note: This may not be possible for shift workers.)  

1. Reducing your bright light exposure at night. Shut off TV and computer screens, devices, and any other sources of blue and bright light at home at least two hours before bedtime. Stick with soft, warm lighting that allows your brain to transition gently from wakefulness to sleep.   

1. Get exercise every day. Tiring out your body via physical activity is crucial for a healthy sleep-wake cycle. 

1. Reduce your food intake at night. Eat dinner at least 2-3 hours before sleep, and try to avoid late night snacking. 

1. Limit alcohol, nicotine, and caffeine consumption at night. All will alter/affect your sleep quality and may make it harder to fall asleep or stay asleep. 

1. Create a restful, pleasant sleep environment. A cool, dark, quiet room with a comfortable bed and proper neck and back support will not only help you fall asleep more easily, but facilitate a full night of deep, restful sleep. 

1. Avoid late-afternoon naps. If you need to nap, try taking a 20 to 25-minute “power nap” to rest your eyes and restore your energy without impairing your sleep.  

Wrapping Up: 

Life can throw a lot of challenges and difficulties your way, all of which can impact your sleep. 

Between a stressful, busy work life, an ever-changing schedule, social and family activities, and the physiological changes that occur as you age, you’re going to spend the rest of your life in a constant struggle to sleep better. 

But as you’ve seen above, it can be done. 

Changing the way you structure your days and nights and what you do with your time can go a long way toward repairing and restoring your circadian rhythm and making absolutely certain you sleep better all night, every night.  

While lifestyle changes are key to restoring your circadian rhythm, sometimes your body needs extra support to achieve truly restful, restorative sleep.

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