Understanding the Circadian Rhythm for Better Sleep

The act of waking up each morning and falling asleep each night is something that most of us take for granted. While the exact amount of sleep one needs can vary from person to person, there’s one fact that remains: to live our best, healthiest life, it’s essential to get enough sleep 一 and a good quality of sleep, at that. But have you ever wondered what it is that makes us wake every morning, and why we tend to grow tired at night? Why does a dimly-lit room so often become an enticing place for a nap, and what invisible force seems to be pulling us awake annoyingly early on our weekend mornings (despite our best attempts for a lie-in), even without that pesky workday alarm? 

It’s because there’s actually a clock in our bodies that guides us through the day and night. This body clock is known as the circadian rhythm. The circadian rhythm is more precious than any other alarm. It’s a biological system that controls our sleep patterns, and tells us when it’s time to wake or to sleep. It is believed that interfering with the sleep-wake cycle too often ー for instance, by staying up to party past midnight, or working until the wee hours of the morning ー can mess with this natural rhythm. Constant disruption to the body clock can lead to serious health consequences一but thankfully, just like other clocks, this one can also be reset. 

If you’ve been struggling to get your sleep patterns back on track, resetting your circadian rhythm could be just what your body needs. Read on to learn about what exactly the circadian rhythm is, how it works, and how to maintain a healthy system that can help you get a better night’s sleep.

According to the National Institute of General Medical Sciences, the circadian rhythm is defined as physical, mental, and behavioral changes that occur within a 24-hour cycle. It is a biological system that guides our sense of wakefulness and alertness, helping our bodies to get ready for each morning and be prepared for sleep. Circadian rhythms naturally exist in most living things. Not only do humans depend on this system, other organisms like animals, plants, and microbes also have their own cycle. This internal alarm connects body systems by sending signals to different body parts, keeping our body functions on schedule based on the time of the day. 

The term “circadian rhythm” was first coined in 1959 by Dr. Franz Halberg, a scientist at the University of Minnesota known to many as the father of Chronobiology: a field that studies the internal timing processes in organisms. The term “Circadian” was derived from the Latin words “Circa Diem,” which mean “about a day” in English.

The circadian rhythm is operated by our cells’ exposure to light. In our eyes, rod and cone cells detect the amount of light. After that, these cells signal the hypothalamus ー an area in the brain responsible for hormone secretion ー to release the type of hormones associated with the light received. When the amount of light received is high, cortisol ー a hormone that makes people feel alert ー will be released. When little to no amount of light is detected, melatonin ー a hormone that helps people sleep, will be secreted. 

The circadian rhythm can be broken down into three phases:

• Morning: This is the beginning of the cycle. The body decreases the release of melatonin and increases the secretion of cortisol. At this phrase, blood pressure also rises sharply, preparing the body to start the day. 

• Noon: The body has the best coordination and cardiovascular activity at this time, and the latter can also contribute to greater muscle strength and faster reaction time. Noon tends to be the most energetic period. 

• Midnight: This is the end of the cycle, when the body temperature rises. Melatonin production increases in response to the onset of darkness, signaling the body to prepare us for sleep. Dr. Halberg proposes that people typically have the deepest sleep at 2 AM.

An irregular circadian rhythm can lead to a number of consequences. Studies suggest that disruptions to the cycle tend to increase one’s risk of developing health issues such as diabetes, obesity, and cancer. Not only does an unhealthy sleep-wake cycle damage physical health, it also has a negative impact on mental well-being. For instance, a disrupted circadian rhythm can trigger a low mood, which in turn can make a person more vulnerable to mental health issues such as depression and anxiety. 

In sleep psychology, an irregular circadian rhythm can also cause circadian rhythm sleep disorders ー a category of sleep disorders that occur when an individual has an atypical sleep-wake pattern. Oftentimes, these can be caused by external factors like night shift work and time zone changes, and internal factors like brain damage and menopause. Common circadian rhythm sleep disorders include:

• Delayed Sleep Phase Disorder: This is characterized by the tendency to fall asleep and wake up later than a usual sleeping time, associated with an irregular time for melatonin release. People with this health issue tend to doze off at least two hours later than when they should naturally be asleep by, usually between 2 AM to 6 AM. 
• Advanced Phase Sleep Disorder: People with this issue tend to sleep and wake earlier than the usual sleeping time. They tend to struggle to stay awake past around 8 to 9 PM, and wake up as early as 3 to 4 AM. 

While there are guidelines for the average amount of sleep a person needs depending on factors such as age and activity level, sometimes, we just have to listen to our body: and it does find ways to tell us when we need more of it. Here are some signs that your body may be sleep-deprived:

• Changes in the skin, such as frequent dark circles under the eyes, or an unnatural pallor
• Heightened and easily-triggered emotional reactions 
• Constant irritability
• Being prone to illness due to a weakened immune system
• Changes in appetite, whether that’s noticeably increased or decreased, not caused by other factors
• Noticeable weight gain or weight loss, not caused by other factors
• Impaired or reduced motor skills
• Difficulty with eyesight, or watery, tired, or sensitive eyes
• Cognitive issues such as memory loss or difficulty focusing or making decisions
• An over-reliance on stimulants such as caffeine or sugar-rich foods 
• Increased cravings for fatty or sugar-rich junk-style foods
• Taking longer to recover from injuries or illnesses
• A decreased libido
• Heightened anxiety or depression

Causes of a circadian rhythm disruption can be temporary ー such as too many late nights on a big work project, bad sleep hygiene, or jet lag, for instance ー or longer-term, such as aging, a medical issue, or a health condition. Consider reducing these disruptors by trying to avoid major changes to a more natural schedule or routine, decreasing the amount of stimulants you consume during the day (such as high-sugar foods and high amounts of caffeine), and creating a better sleep environment. While research into whether blue light-blocking glasses are actually effective or not ー and how much this type of light can affect eye strain and, in turn, sleep ー is ongoing, reducing screen time at least 30-60 minutes before bed has been found to help you get better shut-eye due to the amount of light emitted. If stress and anxiety are affecting your ability to sleep, incorporating mindfulness habits or a meditation practice into your routine can help.

Understanding one’s circadian rhythm ー and knowing how to listen to it to optimize sleep quality ー can have a considerable impact on day-to-day life. Making sure that we get enough restful sleep on a regular basis is essential for our physical, mental, and emotional health. On a physical level, it can affect things like weight gain, heart disease, immune health, blood pressure, appetite, breathing, and eyesight. It can also affect our cognitive functions, including our ability to learn well, focus, or make better decisions, and our moods, alertness, memory, attention spans, and even our ability to think more positively. 

But whether you’re feeling off-kilter due to insomnia or other sleep difficulties, lifestyle factors like jet lag and stress, or having pulled one too many all-nighters, here’s the good news: the circadian rhythm can be reset by changing one’s exposure to lightness and temperature. If you need to make some positive changes to your sleep routine, consistency is key, since experts say it can take anything between two weeks to two months for your circadian rhythm to fully reset. Below are some tips that can help you to improve your body clock.

• Sleep With The Lights Off: Light exposure during bedtime can confuse the brain, misleading it to believe it is daytime, and making the body less likely to fall into a deeper sleep. Switching off the lights can better prepare the body for better sleep. If sleeping in a darker room is not always accessible to you, consider using a comfortable sleep mask over your eyes, to help block out additional light sources.

• Adjust The Temperature: The circadian rhythm suggests that our body temperature increases at night before sleep time. If you live in colder parts of the world, turning on your heater at bedtime can prepare your body for sleep. If the room is too hot, using a fan or air conditioner can help keep your body from overheating while you sleep. Experts say the optimal temperature for good sleep is between 65 to 70 degrees Fahrenheit, or 18.3 to 21.1 degrees Celsius, although this will vary slightly from person to person.

• Avoid Caffeine Consumption: People may think that products with caffeine, such as coffee and tea, can boost your alertness during the day without thinking too much of the consequences on your sleep patterns. However, excessive caffeine, particularly at night, can postpone the release of melatonin and cause a delayed circadian rhythm. Limiting caffeine intake (especially in the later hours of the day) can help your body to release these chemicals more naturally, and maintain a healthier circadian rhythm. 

• Create A Healthier Sleep Environment: Having good sleep hygiene involves paying attention to what could be keeping you from getting better rest, and putting systems in place to remove these issues. For instance, are you taking naps too close to bedtime that are affecting your nighttime sleep habits? Is there a source of noise that’s keeping you awake, which you could put a stop to (or even muffle out with a white noise machine or earplugs if need be)? Do you need to switch your pre-bed reading habit to a non-digital device, or one where the screen lighting is adjusted appropriately? Do you sleep better when you limit reading, talking, or thinking about certain topics before bed, like anxiety-inducing news? It may require some discipline at first to maintain a consistent schedule and create a set of pre-bedtime rituals that help you wind down, but this could go a long way in helping you establish a healthier circadian rhythm.

Want to improve your sleep habits? Join our Holistic Self-Care course to learn practical ways to improve all areas of your well-being, including how to be more well-rested and energetic day-to-day.

Listen to this hypnosis meditation to fall asleep faster and easier anytime you need a deeper rest!

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All of the content on our website is thoroughly researched to ensure that the information shared is evidence-based. For more information, please visit the academic journals and other resources that influenced this article: National Institute of General Medical Sciences - Circadian Rhythms; Introduction to Chronobiology; A Tribute to Franz Halberg, MD; The Role of Retinal Photoreceptors in the Regulation of Circadian Rhythms; Circadian Rhythms of the Hypothalamus: From Function to Physiology; Cortisol; Melatonin: Benefits, Uses, Side Effects and Dosage; Disruption of Circadian Rhythms Accelerates Development of Diabetes through Pancreatic Beta-Cell Loss and Dysfunction; Circadian Disruption Leads to Insulin Resistance and Obesity; Shift Work and Cancer Risk: Potential Mechanistic Roles of Circadian Disruption, Light at Night, and Sleep Deprivation; Circadian Rhythm Sleep Disorders; What Is Delayed Sleep Phase Syndrome?; Advanced Sleep Phase Disorder (ASPD); Let There Be No Light: The Effect of Bedside Light on Sleep Quality and Background Electroencephalographic Rhythms; Effects of Caffeine on the Human Circadian Clock in Vivo and in Vitro.