Circadian rhythm disorders, also known as sleep-wake cycle disorders, are problems that occur when your body’s internal clock, which tells you when it’s time to sleep or wake, is out of sync with your environment.
Your internal clock, called a circadian clock, cycles about every 24 hours. These repeating 24-hour cycles are called the circadian rhythm.
Your body tries to align your sleep-wake cycle to cues from the environment, such as 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 your sleep habits, job, or travel. Or a circadian rhythm disorder can be long-term and caused by aging, your genes, or a medical condition. You may have symptoms such as extreme daytime sleepiness, decreased alertness, and problems with memory and decision-making.
What causes circadian rhythm disorders?
Genetic conditions that affect your brain or hormone 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 sleep-wake cycle and your risk for circadian rhythm disorders may be different from someone else’s? This is controlled by your genes in your DNA. Some people naturally wake early, while others naturally stay up late. Some people can more easily adjust their circadian rhythm to match their environment. If you are one of these people, you may be less likely to develop jet lag disorder and shift work disorder. You may develop circadian rhythm disorders if your patterns do not align with your work, school, or social responsibilities. Talk to your doctor about your symptoms.
What raises your risk of circadian rhythm disorders?
Many things can lead to a circadian rhythm disorder. Some you cannot change, like your age, family history, or sex. Some you can manage, like your lifestyle or occupation.
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 usually go to 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 or genetics: Your 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. Changes in the genes that control your circadian rhythm, called circadian clock genes, can also raise your risk.
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 being exposed at nighttime to artificial light, such as from a TV screen, smartphone, or 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, which raise 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, which raise the risk of delayed sleep-wake phase disorder
- Neurodegenerative diseases, such as Alzheimer’s disease, dementia, and Parkinson’s disease: These conditions are more common in older adults and can increase the risk for irregular sleep-wake phase disorder.
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 exposure to light while caring for a newborn can increase your risk for circadian rhythm disorders.
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 as a result, 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 then 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 falls 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 to when you travel west.
Some people experience social jet lag, which can occur when you go to activities on weekends or days off at much later times than you do 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 your 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 occurs 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, extreme tiredness, and sleepiness while working at night.
- Difficulty falling asleep, staying asleep, or both
- Excessive daytime sleepiness or sleepiness during shift work
- Extreme tiredness and exhaustion
- Decreased alertness and difficulty concentrating
- Impaired judgment in risky situations, such as while driving, 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 deprivation a condition that occurs when you do not get the recommended amount of uninterrupted quality sleep (7-9 hours for adults). 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.
Your doctor may recommend one or more of the following tests:
- Actigraphy involves wearing a small motion sensor for 3 to 14 days to measure your sleep-wake cycles.
- Sleep studies measure how well you sleep and how your body responds to sleep problems.
Your doctor may do other studies to 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 rise and fall over time can help determine the type of circadian rhythm disorder you may have.
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.
- Keep a regular meal schedule, especially if you are a shift worker or sleep at irregular times of the day or night.
- Start 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.
- Avoid daytime naps, especially in the afternoon. However, shift workers may benefit from a short nap before the start of their shift.
- Get regular physical activity. 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.
- Limit caffeine, alcohol, nicotine, and some medicines, especially close to bedtime.
- Manage 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.
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.
Medicines or supplements
Your doctor may recommend melatonin medicines or supplements to help align your sleep-wake cycle with your environment.
- Melatonin medicine, called melatonin receptor agonists, can help 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 for 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. Because of this, the dose and purity of these supplements can vary between brands. Talk with your doctor about how to find safe, effective melatonin supplements, as well as any possible side effects or medicine interactions, especially if you are pregnant or trying to become pregnant. Side effects of melatonin may include excess sleepiness, headaches, high blood pressure, low blood pressure, stomach upsets, and worsening symptoms of depression.
Your doctor may talk to you about other ways to treat the symptoms of circadian rhythm disorders.
- Caffeine may 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, can help you fall asleep faster and stay asleep longer. These medicines may cause side effects and complications, such as muscle weakness and confusion, that may be more severe in older adults and people who have dementia.
- Wake-promoting medicines, such as modafinil and armodafinil, can 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.