Circadian rhythm disorders are problems that occur when your sleep-wake cycle is not properly aligned with your environment and interferes with your daily activities.

You have a biological clock that controls the timing of several activities and functions of your body, including when you go to sleep and wake up. This internal mechanism is called the circadian clock. The circadian clock cycles about every 24 hours. These repeating 24-hour cycles are called the circadian rhythm. The control of your circadian rhythm is a function of certain genes in the DNA called circadian clock genes.

Your body tries to align your sleep-wake cycle to cues from the environment that come, for example, when it gets light or dark outside, when you eat, and when you are physically active. When your sleep-wake cycle is out of sync with your environment, you may have difficulty sleeping, and the quality of your sleep may be poor. Disruptions of your sleep-wake cycle that interfere with daily activities may mean that you have a circadian rhythm disorder.

Disruptions in your sleep patterns can be temporary and caused by external factors such as your sleep habits, job, or travel. Or a circadian rhythm disorder can be long-term and caused by internal factors such as your age, your genes, or a medical condition. Symptoms may include extreme daytime sleepiness, insomnia, tiredness, decreased alertness, and problems with memory and decision-making.

To diagnose a circadian rhythm disorder, your doctor may ask about your sleep habits, suggest sleep tests, a diary to track when and how long you sleep, and test the levels of certain hormones in your blood or saliva. Your treatment plan will depend on the type and cause of your circadian rhythm disorder. Treatment may include light therapy, medicines to help you fall asleep or stay awake, or healthy lifestyle changes including steps to improve your sleep habits. If left untreated, circadian rhythm disorders may increase the risk of certain health problems or lead to workplace and road accidents.

The types of circadian rhythm disorders are advanced or delayed sleep-wake phase disorder, irregular or non–24-hour sleep-wake rhythm disorder, and shift work or jet lag disorder. The type you may have is based on your pattern of sleep and wakefulness.

Advanced sleep-wake phase disorder

If you have advanced sleep-wake phase disorder (ASWPD), you may find it very difficult to stay awake in the early evening and wake up too early in the morning. This can interfere with work, school, or social responsibilities.

Delayed sleep-wake phase disorder

This is one of the most common circadian rhythm disorders. If you have delayed sleep-wake phase disorder (DSWPD), you may fall asleep later than you would like and find it difficult to wake up on time in the morning. Delayed sleep-wake phase disorder often interferes with work, school, or social responsibilities. You may get too little sleep, which can lead to daytime tiredness or anxiety.

Irregular sleep-wake rhythm disorder

If you have irregular sleep-wake rhythm disorder (ISWRD), you may have several short periods of sleep and wakefulness. You may be unable to sleep during the night and take multiple naps during the day due to excessive sleepiness. You may not feel rested after sleep.

Jet lag disorder

This is often a temporary disorder that may affect you if you travel across at least two time zones in a short period. Your sleep-wake rhythm is out of sync with the local time at your destination, so you may feel sleepy or alert at the wrong time of day or night. Jet lag disorder is often more severe when you travel east, compared with traveling west.

Some people experience social jet lag, in which activities on weekends or days off occur at much later times than on weekdays or workdays. This is not considered a disorder.

Non–24-hour sleep-wake rhythm disorder

This type of circadian rhythm disorder occurs when a person’s sleep-wake rhythm is not in sync with the 24-hour day. When this happens, your sleep times may gradually become more delayed. For example, your sleep time may be delayed to the point that you are going to sleep at noon instead of night. This often happens when light exposure is very limited, and it is common in people who are completely blind. You may have periods of insomnia and daytime sleepiness, followed by periods with no symptoms, when your circadian rhythms happen to align with your environment.

Shift work disorder

Shift work disorder affects those who work during the night or on a rotating schedule. Because of your work schedule, you may not be able to get uninterrupted quality sleep when your body needs it. Shift work disorder can cause insomnia, fatigue, and sleepiness while working at night.

You may have a higher risk for circadian rhythm disorders because of internal factors such as your age, your sex, family history and genetics, and certain medical conditions that affect your brain or vision. External factors such as your lifestyle habits, environment, and occupation can also increase your risk.

Age

The rhythm and timing of your sleep-wake cycle can change with age because of changes in your brain. Teens may naturally have a later bedtime than adults, which raises their risk for delayed sleep-wake phase disorder. Older adults, on the other hand, usually sleep and wake up early. This raises their risk for advanced sleep-wake phase disorder. Older adults are also at higher risk for shift work disorder and jet lag disorder.

Environment or occupation

People who work during the night have a higher risk for shift work disorder. Jet lag disorder is more common in pilots, flight attendants, athletes, and people who travel often for business.

Family history and genetics

Your genes may play a role in whether you naturally wake up early in the morning or go to sleep later at night. This genetic preference of an early or late bedtime can raise your risk for advanced or delayed sleep-wake phase disorder if your rhythm is out of sync with your environment or social responsibilities.

Mutations in certain genes can also raise your risk for circadian rhythm disorders. These include the genes that control your body’s circadian clocks and certain genes that affect brain development or health.

Lifestyle habits

Lifestyle habits can raise your risk for circadian rhythm disorders. These include:

• Alcohol use
• Chronic caffeine use
• Frequent air travel
• Illegal drug use
• Lack of exposure to natural light during the day
• Unhealthy sleep habits such as regularly staying up late and nighttime exposure to artificial light, including light from a TV screen, a smartphone, or a very bright alarm clock

Other medical conditions

Several medical conditions can increase your risk for circadian rhythm disorders, including:

• Autism spectrum disorders
• Certain genetic conditions, such as Smith-Magenis syndrome, Angelman syndrome, and Huntington’s disease
• Conditions that affect eyesight, such as blindness and macular degeneration. This raises the risk for non-24-hour sleep-wake rhythm disorder.
• Conditions that cause damage to the brain, such as traumatic brain injuries, strokes, and brain tumors
• Mental health conditions, such as bipolar disorder, major depression, obsessive-compulsive disorder, and schizophrenia. This raises the risk of delayed sleep-wake phase disorder.
• Neurodegenerativediseases, such as Alzheimer’s disease, dementia, and Parkinson’s disease. These conditions are more common in older adults and can increase your risk for irregular sleep-wake phase disorder.

How do neurodegenerative conditions lead to circadian rhythm disorders?

Neurodegenerative diseases such as Alzheimer’s disease and dementia can damage brain cells that process light and other signals from the environment. Without correct information, your body makes less melatonin and at different times of the day than expected. This can lead to irregular sleep-wake rhythm disorder or a complete reversal of the normal sleep-wake cycle.

People who have neurodegenerative conditions and are living in nursing homes may not have a clear pattern of day and night. They may have few social interactions during the day and be awakened for medicine and care throughout the day and night. This can lead to a disrupted sleep-wake cycle, which may cause circadian rhythm disorders.

Sex

Men are more likely to have advanced sleep-wake phase disorder than women.

Women may be more likely to experience circadian rhythm disorders at certain stages of life.

• Hormonal changes that happen during pregnancy, after childbirth, and at menopause can cause problems with sleep.
• Discomfort during pregnancy may also prevent good-quality sleep.
• After childbirth, sleep interruptions and nighttime exposureto light while caring for a newborn can increase your risk for circadian rhythm disorders.

Circadian rhythm disorders occur when your sleep-wake cycle is out of sync with your environment. Many factors, both internal and external, can cause you to have problems sleeping and raise your risk for a circadian rhythm disorder.

Genetic conditions that affect your brain or hormones can cause circadian rhythm disorders. For example, Smith-Magenis syndrome is a genetic condition that may affect how much or how often your body makes the hormone melatonin, which helps you sleep. Sleep patterns may be completely reversed, causing daytime sleepiness and wakeful nights.

Did you know that your natural circadian rhythm and your risk for disorders may be different from someone else's?

The sleep-wake cycle can be different for different people. Some people naturally wake early, while others naturally stay up late. These patterns are controlled by your genes, among other factors. You may develop circadian rhythm disorders if your patterns do not align with your work, school, or social responsibilities. Some people can more easily adjust their circadian rhythm to match their environment. This adaptable nature makes you less likely to develop jet lag disorder and shift work disorder.

Signs and symptoms of circadian rhythm disorders can vary depending on the type of circadian rhythm disorder you have and how severe your condition is. Many of the symptoms of circadian rhythm disorders occur because you are not getting enough good-quality sleep when your body needs it. Undiagnosed and untreated circadian rhythm disorders may increase your risk of certain health conditions or cause workplace or road accidents.

Signs and symptoms

Common symptoms of circadian rhythm disorders include:

• Consistent difficulty falling asleep, staying asleep, or both
• Excessive daytime sleepiness or sleepiness during shift work
• Fatigue and exhaustion
• Lethargy
• Decreased alertness and difficulty concentrating
• Impaired judgment and trouble controlling mood and emotions
• Aches and pains, including headaches
• Stomach problems, in people who have jet lag disorder

How do circadian rhythm disorders affect judgment?

Circadian rhythm disorders often cause sleep deficiency, a condition in which you do not get the recommended amount of uninterrupted quality sleep. Sleep deprivation can change how well your brain judges risky situations and behaviors. When you do not get enough sleep, you may underestimate the risks and overestimate the rewards of certain situations. This may lead you to make riskier choices than you would have made if you were well rested. Not getting enough sleep when you need it can also increase your risk for accidents, such as those caused by drowsy driving after working a night shift, for example.

Complications

Circadian rhythm disorders may increase your risk for the following health conditions:

• A weakened immune system, which can lead to infections and poor recovery from illnesses
• Cardiovascular diseases, such as atherosclerosis or stroke
• Cognitiveand behavioral disorders, such asdecreases in attention, vigilance, concentration, motor skills, and memory. These can lead to reduced productivity, workplace mistakes, or road accidents. In teens and young adults, circadian rhythm disorders can cause risky behavior and problems with concentrating at school, controlling emotions, and coping with stress.
• Digestive disorders, such as stomach ulcers, gastroesophageal reflux disease (GERD), and irritable bowel syndrome. Circadian rhythm disorders may influence the signaling from the brain to the gastrointestinal tract. They may also increase inflammation in the bowel, which can lead to digestive symptoms.
• Fertility problems. Circadian rhythm disorders may disrupt the hormone cycle that controls fertility and reproduction.
• Metabolism disorders,which can lead to diabetes, metabolic syndrome, and overweight and obesity
• Mood disorders, including irritability, anxiety, and depression
• Worsening of other sleep disorders, such as sleep apnea

Do you want to learn more about how circadian rhythm disorders cause problems with metabolism in shift workers?

When shift work triggers a circadian rhythm disorder, it can disrupt your metabolism in a few ways. Normally, your biological clock helps control your hunger hormones. However, when you do not get enough good-quality sleep, your body makes less leptin, the hormone that tells your body when you are full, and more ghrelin, the hormone that tells your body you are hungry. You may respond by eating larger amounts of food than normal, as well as more fatty, sweet, and salty foods.

To diagnose a circadian rhythm disorder, your doctor may review your medical history; ask about your symptoms, sleep patterns, and environment; do a physical exam; and order diagnostic tests.

Medical history and physical exam

Your doctor will want to learn about your signs and symptoms, risk factors, your personal health history, and your family health history to help diagnose a circadian rhythm disorder. To do this, your doctor may do the following:

• Ask when, how long, and how well you sleep.
• Ask when your symptoms began. Symptoms that have lasted for three months or more may indicate a circadian rhythm disorder.
• Ask about your personal and family history of health conditions.
• Perform a physical examination.

Diagnostic tests

Your doctor may have you undergo or use some of the following tests and measurements:

• A sleep diary to help you keep track of when and how long you sleep
• Actigraphy, in whichyou wear a small motion sensor for three to 14 days to measure your sleep-wake cycles
• Sleep studies to measure how well you sleep and how your body responds to sleep problems.
• Other studiesto look at your natural patterns of sleep and wakefulness. Your doctor may repeatedly measure your body temperature and the levels of melatonin and cortisol in your blood or saliva. The way these factors rise and fall over time can help determine the type of circadian rhythm disorder you may have.

Do you want to learn more about how melatonin, cortisol, and body temperature work in someone with a healthy sleep cycle?

When you have a healthy sleep pattern,melatonin levels usually start to rise about two hours before your normal bedtime. Melatonin reaches its highest level while you sleep and goes down as you wake up. Your cortisol levelsare usually highest early in the morning and fall throughout the day. Cortisol helps prepare your body to wake up. Body temperaturetypically falls during the night and rises in the early hours of the morning. All these changes are controlled by your circadian clocks.

Ruling out other medical conditions

To rule out other causes of your symptoms, your doctor may do the following:

• Ask about your use of caffeine, nicotine, alcohol, or illegal drugs, as well as your exposure to artificial light at night. These lifestyle habits may cause insomnia or tiredness.
• Ask you to keep a sleep diary or have a specific type of sleep study to rule out other problems with sleep, such as insomnia, sleep apnea, and narcolepsy
• Ask you whether you have chronic pain that may be preventing good-quality sleep
• Examine you for heart or lung conditions that may prevent good-quality sleep
• Examine you for large tonsils or small airways to help rule out sleep apnea
• For women, ask whether you are pregnant or undergoing menopause

Treatments for circadian rhythm disorders aim to reset your sleep-wake rhythm to align with your environment. Your treatment plan will depend on the type and severity of your circadian rhythm disorder. The most common treatments are healthy lifestyle changes, bright light therapy, and melatonin. Often, your doctor will recommend a combination of these treatments.

Healthy lifestyle changes

To help reset your sleep-wake cycle, your doctor may recommend that you establish a daily routine with set activities that happen during the day and another set of activities that happen at night. This may help manage the symptoms of circadian rhythm disorders caused by internal or external factors. A daily routine is especially important if you have complete blindness or cannot tolerate changes to your light exposure. Your daily routine may include:

• Adopting a regular meal schedule, especially if you are a shift worker or sleep at irregular times of the day or night.
• Adopting a regular bedtime routine. Sleep in a cool, quiet place and follow a relaxing bedtime routine that limits stress. These practices, along with regular sleep and waking times, can help you fall asleep faster and stay asleep longer.
• Avoiding daytime naps, especially in the afternoon. However, shift workers may benefit from a short nap before the start of their shift.
• Exercising regularly. Your doctor may recommend getting regular physical activity during the daytime and avoiding exercising close to bedtime, which may make it hard to fall asleep.
• Limiting your intake of caffeine, alcohol, nicotine, and some medicines, especially close to bed time
• Managing your exposure to light. Light is the strongest signal in the environment to help reset your sleep-wake cycle. You may need more sunlight during the day and less artificial light at night from TV screens and electronic devices. Artificial light can lower your melatonin levels, making it harder to fall asleep. Light-blocking glasses, screen filters, or smartphone apps can help dim the light from your electronic devices. Dim lighting for a period before bed may also help reduce the symptoms of a circadian rhythm disorder. For shift workers, wearing light-blocking glasses when you are outside during the day may help.

Light therapy

Your doctor may suggest that you try light therapy to treat some types of circadian rhythm disorders. With this approach, you plan time each day to sit in front of a light box, which produces bright light similar to sunlight. Light visors and light glasses may also be effective. Light therapy may help adjust how much melatonin your body makes to reset your sleep-wake cycle.

• To move your sleep and wake times earlier, use the light box when you wake up in the morning. This may also help reduce daytime sleepiness. This method may be used to help treat delayed sleep-wake phase disorder, irregular sleep-wake rhythm disorder, and jet lag disorder when you travel east.
• To move your sleep and wake times later, use the light box late in the afternoon or early in the evening. This method may be used to help treat advanced sleep-wake phase disorder, shift work disorder, and jet lag disorder when you travel west.

Side effects of light therapy may include agitation, eye strain, headaches, migraines, and nausea. Ask your doctor before using light therapy if you have an eye condition or use medicines that make you sensitive to light.

Melatonin medicines or supplements

Your doctor may recommend melatonin medicines or supplements to help align your sleep-wake cycle with your environment. The choice depends on the type and severity of your circadian rhythm disorder. Options may include the following:

• Melatonin receptor agonists are medicines to treat non–24-hour sleep-wake rhythm disorder. Side effects can include dizziness and fatigue.
• Melatonin supplements are lab-made versions of the sleep hormone that your doctor may recommend to treat delayed sleep-wake phase disorder, irregular sleep-wake rhythm disorder, and non–24-hour sleep-wake rhythm disorder. These supplements are not regulated by the U.S. Food and Drug Administration. Thus, the dose and purity of these supplements can vary. Talk with your doctor about how to find safe, effective melatonin supplements, as well as any possible side effects or medicine interactions. Side effects of melatonin may include excess sleepiness, headaches, high blood pressure, low blood pressure, stomach upsets, and worsening symptoms of depression.

These medicines may not be recommended for people who have dementia or epilepsy, or who take the blood thinning medicine warfarin. Other people who need to consult a doctor before taking these medicines include women who are pregnant, trying to become pregnant, or breastfeeding.

Other medicines which may be used to treat the symptoms of circadian rhythm disorders include:

• Beta blockers to reduce the levels of melatonin in your body during the day
• Caffeine to help prevent daytime sleepiness. Your doctor may recommend that you avoid caffeine within eight hours of your desired bedtime.
• Sleep-promoting medicines, such as benzodiazepines and zolpidem, to help you fall asleep faster and stay asleep longer. These medicines may cause side effects and complications that may be more severe in older adults and people who have dementia. These complications can include confusion, headaches, poor medicine interactions, long-term dependence, muscle weakness, falls, and nausea.
• Wake-promoting medicines, such as modafinil and armodafinil, to help you stay alert and improve performance during shift work. The effects of these medicines may last only for a short time, and you may still experience some sleepiness.

Currently, there are no screening methods to determine who will develop circadian rhythm disorders. Your doctor may ask you about your sleep habits in childhood and the last several years, and if you have performed shift-work. If you are at risk for circadian rhythm disorders, your doctor may recommend certain lifestyle changes to help prevent a circadian rhythm disorder.

Preventive strategies

To help lower your risk of circadian rhythm disorders, your doctor may recommend that you make healthy lifestyle changes and avoid bright light and caffeine close to your bedtime. While caring for a newborn at night, keep the lights as dim as possible.

You may be able to prevent a circadian rhythm disorder caused by external factors such as your environment.

The following steps may help prevent shift work disorder:

• Take a short nap before your night shift to help prevent sleepiness at work.
• Adopt a sleep schedule on your days off that overlaps with your sleep time on work days.
• Avoid multiple schedule switches between day and night shifts, if possible.

The following steps may help prevent jet lag disorder:

• A few days before travelingacross several time zones, begin adjusting your sleep-wake cycle to match the time at your destination. You may gradually change your sleep schedule and use bright light to help advance or delay your waking time.
• If you can, arrive at your destination a few days before an important event, to help you gradually adjust to the local time. Your body adjusts to the time at your destination at a rate of 1 to 1.5 time zones per day.
• Spend plenty of time outside at your destination. Outdoor light may shorten symptoms of jet lag.

If you have been diagnosed with a circadian rhythm disorder, it is important that you continue your treatment. Follow-up care can vary depending on your response to treatment and whether your condition is caused by internal factors, such as a medical condition, or external factors, such as your environment.

Follow your treatment plan

It is important that you follow your doctor’s instructions to help avoid the symptoms and complications of circadian rhythm disorders. You may need to maintain a regular daily schedule, take your medicines as prescribed, and follow your doctor’s instructions for light therapy even when your condition improves. If your circadian rhythm disorder continues after appropriate lifestyle changes and treatments, you may need to adapt your daily routine to an early or late sleep phase.

Receive routine follow-up care

Talk with your doctor about how often to schedule office visits and medical tests. Between visits, tell your doctor if you have any new symptoms, if your symptoms worsen, or if you have any complications because of your medicines.

Monitor your condition

To monitor your condition and to help prevent complications, your doctor may recommend regular testing. These tests and measurements may include:

• Actigraphy testing to check periods of sleep and activity
• Body weight
• Melatonin levels
• Metabolism

Your doctor may also recommend that you keep a sleep diary to monitor improvements in your pattern of sleep and wakefulness and in your quality of sleep.

Learn precautions to help you stay safe

To avoid accidents caused by fatigue and daytime sleepiness, it is important to identify when you are too tired to drive, operate heavy machinery, or work. Consider using public transportation if you are too tired to drive.