What Are Circadian Rhythm Sleep-Wake Disorders?

Circadian rhythm sleep-wake disorders are conditions in which wake and sleep times get out of order. Of the more than 80 different sleep disorders, 6 fall into the category of circadian rhythm sleep disorders. The 6 types of circadian rhythm sleep disorders are:^1-3

• Advanced sleep-wake phase
• Delayed sleep-wake phase
• Irregular sleep-wake rhythm
• Jet lag
• Non-24 hour sleep-wake rhythm
• Shift work disorder

Circadian rhythm disorders may overlap with other sleep disorders such as sleep apnea.²

What is a circadian rhythm?

Circadian rhythms are the body’s timekeeping system. The body follows certain physical, mental, and behavioral changes each day, many triggered by light and darkness. Sleeping at night and being awake during the day is just one example of a circadian rhythm. Circadian rhythms control things like the production of the hormone, melatonin, which makes you sleepy.⁴

What causes circadian rhythm sleep disorders?

People can throw off their internal body clock in a number of ways. The most common are shift work, travel across different time zones, and exposure to lighted devices long after it is dark outside. These sleep disorders may also crop up during certain times of life. For example, delayed sleep-wake phase is common in teenagers. Advanced sleep-wake phase is common in the elderly.

Types of circadian rhythm sleep disorders

Advanced sleep-wake phase

This occurs when a person goes to sleep several hours before normal bedtime and wakes much earlier than other people. Bedtime is usually between 6 p.m. and 9 p.m. These people may be called “early birds.” It is more common as people age.³

Delayed sleep-wake phase

This occurs when a person goes to sleep 2 or more hours later and wakes up later than others. These people may be known as “night owls” or “evening people” rather than “morning people.” Overall sleep quality tends to be normal, but the person’s body clock may not fit school or work needs. Between 7 percent and 16 percent of people may have it. It is more common in teens and young adults.³

Irregular sleep-wake rhythm

Describes when a person naps throughout a 24-hour period rather than following a consistent pattern of sleeping at night and waking up in the morning. There is no one main sleep time. It is rare and can cause problems for the caregiver since the person may wander around the house at night and get hurt.³

Non-24 hour sleep-wake rhythm

This occurs when a person’s sleep time shifts a bit later each day until they are not sleeping until morning. Then, their sleep time shifts again to evening, and back again to morning. About half of all blind people have a non-24 hour sleep-wake disorder. This is because their eyes do not “see” light and set the brain for sleeping or waking. It is rare in people who are not blind.³

Shift work disorder

This occurs when changing work shifts mean that the body cannot sleep or wake on a regular schedule. Or, your body is sleepy when you need to be at work at night, and awake when you have time to sleep during the day. This creates constant fatigue. Not everyone who works a consistent shift has this sleep disorder. Some people’s bodies adjust after several weeks.³

Jet lag

Jet lag is a temporary sleep disorder. It occurs when someone travels across at least 2 time zones, usually by flying, and the body has trouble adjusting to the new time. Your body clock is set to the old sleep and wake time and takes 1 day to adjust for every hour of time difference.³

Other types of sleep disorders

• Insomnia
• Sleep-related breathing disorders such as sleep apnea
• Sleep-related movement disorders such as restless legs syndrome and periodic limb movement disorder
• Hypersomnias such as narcolepsy
• Parasomnias such as sleepwalking, sleep eating, and bedwetting