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What Are Circadian Rhythms and How Do They Affect Sleep?
by BetterSleep
3 min read
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Circadian rhythms are the natural, internal processes that regulate the sleep cycle and repeat roughly every 24 hours. These rhythms play a crucial role in determining when we feel alert and when we feel tired.

Disruptions to our circadian rhythm can lead to difficulties with falling asleep and staying asleep, as well as overall sleep deficiency. Circadian rhythms are essential to many aspects of optimal health and daily functioning. The most recognizable and well-known of these is the sleep-wake cycle.

Understanding how these rhythms work can help us better manage our sleep patterns and improve our overall health and well-being. The more you can do to adhere to your body and your mind’s natural rhythms, the better you’ll sleep.

Circadian Rhythms – The Basics

Circadian rhythms describe the 24-hour cycle of behaviors and mental and physical changes you experience daily. Most animals have some version of this cycle, dictated largely by light and dark and coinciding with day and night.

The brain has a circadian clock that regulates daily changes. Known as thesuprachiasmatic nucleus, it takes input from the eyes to keep time. The purpose is to optimize the body’s functions based on the time of day.

How Light Exposure Affects Circadian Rhythms

Circadian rhythms are controlled by the hypothalamus, which is part of the brain. The hypothalamus is responsible for a number of activities, including controlling the body’s temperature and releasing hormones. It also regulates circadian rhythms.

Circadian rhythms are important because they control many of the body’s functions, such as when we feel tired or hungry.

The light exposure that we experience throughout the day can affect our circadian rhythms. The most important factor in regulating our circadian rhythms is daylight. When we are exposed to daylight, our brains release less melatonin, which helps to regulate our sleep-wake cycles.

Melatonin is produced in response to darkness, so it is important to get a good night’s sleep and avoid looking at screens before bedtime.

Exposure to artificial light can also affect our circadian rhythms. Blue light, which is emitted by screens and other electronic devices, can interfere with melatonin production and disrupt our sleep-wake cycles. This is why it is important to avoid using screens in the hours before bedtime.

How Do Circadian Rhythms Affect Sleep?

One of the most important aspects of the 24-hour cycle of circadian rhythms is that we sleep at night and remain awake during the day. It does this in a few different ways:

  • Melatonin is a hormone that makes you sleepy. It is suppressed during the day, in daylight, and released as it gets dark at night.
  • Cortisol is a hormone that makes you more alert. Your body releases more of it in the morning.
  • Body temperature drops at night when you sleep and rises during the day.
  • Metabolic rates differ at night and during the day to match when you should be sleeping and when you should be eating.

The sleep-wake cycle is a crucial part of circadian rhythms. Many of the signals are directed at making you sleepy at night and alert during the day. The result should be that you get restorative, restful sleep every night, which in turn supports your daytime activities.

How Else Do Circadian Rhythms Affect Us?

Sleeping and waking are some of the most obvious effects of circadian rhythms, but they are not the only ones. Circadian rhythms also affect:

  • Weight and other dietary factors, like blood sugar, metabolism, and cholesterol
  • Mental health
  • The immune system
  • DNA repair processes, which impact cancer risk
  • Neurodegenerative diseases, like dementia

What Factors Can Change Circadian Rhythms?

Because circadian rhythms impact so many aspects of health, it is important to avoid or minimize disruptions to them. Many factors can change your circadian rhythms, disrupting the cycle and causing harm.

Anything that disrupts normal sleep patterns, for example, can be a problem. Working night shifts (which could lead to shift work sleep disorder) or traveling and having to cope with jet lag will change the cycle. A consistent or repeated pattern of sleep disturbance that causes insomnia or excessive drowsiness is indicative of shift work disorder.

Also problematic are any lifestyle changes that keep you up late or force you to rise well before the sun.

Stress and mental illness can impact the cycle, too, as can some physical health conditions. These include brain damage, head injuries, and blindness. Some medications can also be disruptive.

Even if you have none of these specific issues, poor sleep habits can damage your normal circadian rhythm. To sleep better and be healthier, stick to a regular 24-hour routine that includes going to bed at the same time every night and getting up at the same time in the morning.

Get exposure to sunlight during the day.

As a bonus, get exercise outdoors. Make sure your sleep environment is cool, relaxing, and dark. Avoid screens before bed as well as alcohol, caffeine, and heavy meals. Don’t nap in the afternoon or evening.

Circadian rhythms are essential to so many aspects of normal functioning. Follow that rhythm and practice good sleep habits, and you should feel rested and restored during the day.

Circadian Rhythm Sleep Disorders

Circadian rhythm disorder is a type of sleep disorder that impacts a person’s circadian rhythm. This means that their body’s natural sleep and wake cycles are disrupted. There are a few different types of circadian sleep disorders, each with their own distinct symptoms.

The most common type is jet lag, which is caused by traveling across different time zones. Other types of circadian rhythm disorders include delayed sleep phase disorder, advanced sleep phase disorder, and irregular sleep-wake syndrome.

Jet Lag

Jet lag is a type of circadian rhythm sleep disorder caused by air travel across time zones. When the body’s natural circadian rhythms are disrupted, jet lag can result. Symptoms of jet lag include fatigue, headache, nausea, and difficulty concentrating.

Jet lag can make it difficult to fall asleep and stay asleep, and can also affect performance and alertness. There is no cure for jet lag, but there are ways to help minimize its effects.

For example, try to adjust your schedule gradually before your trip, drink plenty of water and avoid caffeine and alcohol, and get plenty of rest before your flight.

Delayed Sleep Phase Syndrome

One of the most common circadian rhythm sleep disorders is delayed sleep phase syndrome (DSPS), which is characterized by difficulty falling asleep and/or waking up in the morning. People with DSPS often have trouble staying asleep throughout the night and feel best when they stay up late and sleep in late.

Other symptoms of DSPS can include fatigue, poor concentration, and irritability. There is no cure for DSPS, but there are treatments that can help people manage their symptoms. Some common treatments for DSPS include chronotherapy (adjusting bedtime and wake time gradually), light therapy, and medication.

Advanced Sleep Phase Syndrome

Advanced sleep phase syndrome (ASPS) is a circadian rhythm sleep disorder that is characterized by an earlier-than-normal bedtime and wake time. Individuals with ASPS often report feeling very sleepy in the evening and have difficulty staying awake past their early bedtime.

ASPS is most commonly seen in older adults, and it is estimated that about 1-5% of the population suffers from this disorder.

There are several theories as to why people develop ASPS. One theory suggests that the disorder may be caused by a misalignment between the internal body clock and the external environment (i.e. working a night shift or traveling across multiple time zones).

Another theory suggests that ASPS may be caused by a problem with the brain’s “sleep gate” - a region that controls when we fall asleep.

There is no cure for advanced sleep phase syndrome, but there are treatments that can help to improve sleep quality and reduce daytime sleepiness. Some common treatments include: bright light therapy, melatonin supplements, sleep medicine, and behavioral therapy.

Irregular Sleep-Wake Syndrome

Irregular sleep-wake syndrome (ISWS) is a circadian rhythm sleep disorder that is characterized by an irregular sleep-wake rhythm. People with this disorder often have trouble going to sleep and staying asleep at night, and they may also experience excessive sleepiness during the day.

Other symptoms of ISWS can include restless legs syndrome, problems with concentration and memory, and mood swings. The cause of ISWS is unknown, but it is believed to be related to problems with the body’s internal clock.

There is no cure for ISWS, but treatment options include behavioral therapies, medications, and lifestyle changes.

Causes of Circadian Rhythm Sleep Disorders

Disruptions to The Body’s Natural Clock

There are many possible causes of circadian rhythm sleep disorders, including disruptions to the body’s natural clock. Some common causes of disruptions to the body’s natural clock include shift work, jet lag, and exposure to artificial light late at night.

These can all disrupt the body’s natural sleep-wake cycle and lead to problems with sleeping.

Hormonal Changes

Circadian rhythm sleep disorders are caused by changes in the body’s hormones. The most significant hormone that affects circadian rhythm is melatonin. Melatonin is produced by the pineal gland and tells the body when it is time to sleep. When the body’s melatonin levels are low, the person will have difficulty falling asleep and staying asleep.

Other hormones that can affect circadian rhythm are cortisol and testosterone. Cortisol is a stress hormone and its levels vary throughout the day. When cortisol levels are high, it can be difficult for a person to fall asleep.

Testosterone is a hormone that is released in the morning and helps to keep people alert. When testosterone levels are high, it can be difficult for a person to fall asleep at night.

Hormonal changes such as those that occur during menopause can also disrupt the body’s natural sleep-wake cycle and cause circadian rhythm sleep disorders.

Medical Conditions

Circadian rhythm sleep disorders can be caused by medical conditions. Conditions that can disrupt the body’s natural circadian rhythm include diabetes, thyroid disease, and rheumatoid arthritis.

Patients with these conditions may have difficulty sleeping at night and feel sleepy during the day. Treatment for circadian rhythm sleep disorders depends on the underlying cause. If the condition is treated, the sleep disorder may improve.


Circadian rhythm sleep disorders (CRSDs) are a type of sleep disorder that affect the timing of sleep. They can be caused by many things, including medications. Medications that can cause CRSDs include those that are used to treat psychiatric disorders, such as antidepressants and antipsychotics, as well as drugs used to treat other health conditions, such as hypertension and asthma.

These medications can disrupt the body’s natural circadian rhythm. This can lead to problems with sleep onset and sleep maintenance, as well as changes in the body’s normal daily rhythms, such as changes in body temperature and hormone levels.

People who take these medications should be aware of the potential for CRSDs and should talk to their doctor if they experience any problems with their sleep. There may be alternative medications available that do not disrupt the circadian rhythm.

Symptoms of Circadian Rhythm Sleep Disorders

If you are experiencing any of these symptoms, it is important to see a doctor to determine if you have a circadian rhythm sleep disorder. Treatment options may include changes to your sleep schedule, medications, or therapy.

Excessive Daytime Sleepiness

CRSD can cause a person to feel excessively sleepy during the daytime. This is because the body’s natural circadian rhythm is out of sync, causing the person to feel more fatigued than normal.

Mood Swings

Mood swings are a symptom of CRSD. People with CRSD may experience mood swings due to changes in their sleep-wake cycle.

These changes can cause people to feel tired, irritable, or angry. Mood swings can also affect a person’s ability to think clearly and make decisions.

Difficulty Focusing or Concentrating

CRSD can often cause problems with focus and concentration. This is because when a person’s body is not in sync with its natural sleep-wake cycle, it can be difficult to stay focused and alert.

Other symptoms of CRSD can include problems with memory or decision-making.


Irritability is a common symptom of CRSD. People with circadian rhythm sleep disorders often have trouble sleeping and feel irritable during the day. This can cause problems in relationships, at work, and in other areas of life.


Fatigue is one of the most common symptoms of CRSDs. This fatigue can be both physical and mental, and it can make it difficult to do everyday activities. People with CRSDs often feel exhausted even after a good night’s sleep, and they may have trouble staying awake during the day.

How to Manage Circadian Rhythm Sleep Disorders

There are many things a person can do to help manage CRSD. First, it is important to understand what these disorders are and how they may be affecting your sleep.

There are many different types of CRSD, so it is important to work with a doctor to determine which type you have. Once you know the type, there are many things you can do to help manage the disorder. These include:

Creating a Regular Sleep Schedule

A regular sleep schedule is one of the best ways to manage CRSD. Going to bed and waking up at the same time every day helps to regulate your body’s natural sleep-wake cycle.

This can be especially helpful for people with delayed or advanced circadian rhythms, which can make it difficult to fall asleep and wake up at the desired times.

There are a few things you can do to help create a regular sleep schedule. First, try to make sure that you have a set bedtime and wake-up time. Second, avoid using electronic devices in bed, as the blue light they emit can disrupt your natural sleep rhythm.

Finally, establish a relaxing bedtime routine that includes activities like reading or listening to calm music.

Avoiding Caffeine and Alcohol Before Bed

Caffeine and alcohol are both stimulants that can disrupt your circadian rhythm and prevent you from getting a good night’s sleep. Caffeine is a diuretic, meaning it makes you urinate more often, which can lead to dehydration.

Alcohol is a depressant that can interfere with the quality of your sleep. It’s best to avoid caffeine and alcohol before bed if you’re struggling with CRSD.


Another way to manage CRSD is to take medications that help to regulate the body’s natural sleep-wake cycle. There are several different types of medications that can be used to treat CRSD.

One type of medication that can be used to treat CRSD is called a chronobiotic. A chronobiotic is a medication that helps to regulate the body’s natural sleep-wake cycle.

Another type of medication that can be used to treat CRSD is called a stimulant. A stimulant is a medication that helps to increase the body’s energy levels.

Regular Exercise

Regular exercise is a great way to manage CRSD. Exercise helps to regulate your body’s clock and can help you get to sleep and stay asleep. It’s also a great way to relieve stress and anxiety, which can also interfere with sleep.

Try to get in at least 30 minutes of exercise every day, and make sure to schedule it for times of the day when you have the most energy.

Light Therapy

Light therapy is a way to manage CRSD. This type of therapy uses light to help your body reset its natural sleep-wake cycle. During light therapy, you sit or work in front of a special light box for a set amount of time each day. The light box emits bright light that mimics natural outdoor light.

Light therapy has been shown to be an effective treatment for CRSD. It can help you get back on track with your natural sleep-wake cycle, and it can also improve your mood and energy levels.

If you think you might have a Circadian rhythm sleep disorder, talk to your doctor about whether light therapy might be the right treatment for you.

How to Regulate Your Circadian Rhythm for Better Sleep

The circadian rhythm is a natural process that regulates the body’s sleep-wake cycle. It can be disrupted by external factors such as light and noise, as well as by internal factors such as stress and illness.

Disruptions to the circadian rhythm can lead to sleep problems such as difficulty falling asleep, difficulty staying asleep, and excessive daytime sleepiness.

There are several ways to help regulate the circadian rhythm and improve sleep:

  • Get plenty of bright sunlight during the day. Sunlight helps to synchronize the body’s internal clock with its external environment.
  • Avoid bright light exposure in the hours before bedtime. Blue light, which is emitted by electronic devices such as smartphones and TVs, can interfere with the body’s ability to produce melatonin, a hormone that helps promote sleep.
  • Establish a regular sleep schedule and stick to it as much as possible. Going to bed and waking up at the same time each day helps to set the body’s internal clock.
  • Avoid working or studying in bed. Doing work or studying in bed can make it harder to fall asleep when it’s time for bed.
  • Keep a cool, comfortable environment in your bedroom. A cool room is more conducive to sleep than a warm one.

Are There Any Foods or Drinks That Can Help With Regulating Circadian Rhythms?

There are a few different foods and drinks that can help with regulating circadian rhythms and getting a good night’s sleep. One is melatonin, which is a hormone that helps regulate the body’s sleep-wake cycle. Foods that contain melatonin include cherries, tomatoes, and bananas.

Another food that can help with sleep is tryptophan, which is an amino acid that helps the body produce serotonin, a neurotransmitter that has a calming effect. Tryptophan is found in foods such as turkey, chicken, eggs, and dairy products.

Finally, magnesium is also known to promote relaxation and help with sleep. Foods high in magnesium include leafy green vegetables, legumes, nuts, and seeds.


When it comes to getting a good night’s sleep, having a regulated circadian rhythm is key. By understanding how your circadian rhythm works and what affects it, you can take steps to help regulate your sleep schedule.

Factors like exposure to light and exercise can play a role in keeping your rhythm on track, which can in turn help you get the rest you need.

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