One fourth of all chronic sleep disorders are the result of a mismatch between the body's internal clock and the external 24-hour schedule. These sleep-timing problems are called circadian rhythm sleep disorders because 'circadian' describes the body's daily sleep/wake hormone regulation (Circadian is Latin for 'about a day'). In addition, most other sleep disorders can damage circadian rhythms and further compound sleep problems. The National Institute of Health estimates that over 35 million Americans suffer from circadian rhythm disorders.
Our daily activity and sleep rhythms are regulated by a control center in the hypothalamus region of the brain called the Suprachaismatic Nucleus (SCN) or in layman's terms, the body clock. The body clock needs to receive signals to tell it when to shut down and prepare for sleep and when to produce the active waking hormones. The most powerful signaler or 'zeitgeber' is bright light such as sunshine. Other zeitgebers are darkness, certain sounds, weather, mealtimes, etc. When the body clock cannot receive these signals correctly, it malfunctions, causing circadian rhythm disorders.
When we're younger, our body clocks tend to run a bit slow, and so when they don't get the right signals, they cause a Delayed Circadian Rhythm Disorder . As we mature, our body clocks tend to speed up, causing Advanced Circadian Rhythm Disorder. Women suffer at three times the rate as men, and they experience circadian rhythm disorders earlier in their teens. Men usually notice problems in their late teens. Women's body clocks also speed up sooner than men, usually in their early 40's. Most men's clocks don't start speeding up or advancing until they reach their 60's.
Although advanced and delayed circadian rhythms account for most circadian sleep disorders, a significant number of people also suffer from the following disorders: Circadian Amplitude Disorder, Non 24-hour Sleep/Wake Cycle (or Free-running Circadian Rhythm Disorder) , and Bimodal Circadian Rhythm Disorder (or Irregular Sleep/Wake Cycle) . Each circadian rhythm disorder is discussed in detail below:
Delayed Circadian Rhythm Disorder (DCR) means your body clock is running slower than a normal circadian rhythm (24-hour period). Your body doesn't 'wake up' until later in the morning or day. You may have difficulty getting started in the morning, you may feel a bit groggy or down during part of the day, and you may experience a second wind later in the evening. Those with DCR are often referred to as night owls, and find it easier to stay up late at night. Although some DCR sufferers have little trouble falling asleep, almost all have difficulty getting up or getting started in the morning.
You may experience one or more of the following symptoms:
Because your daily cycle, or circadian rhythm is running slow, your pineal gland releases the nighttime hormone melatonin too late, often causing you to fall asleep later (Some DCR sufferers tend to oversleep). When you need to get up, your body clock may think it is still midnight and is still producing the nighttime hormones. This is why it may take several hours to feel active and energetic. And because you don't receive the proper amount or type of sleep, your energy, alertness and ability to function may also be diminished.
Advanced Circadian Rhythm Disorder (ACR) means your body clock is running faster than a normal 24-hour period. This means you tend to run out of energy before the 'day' or 24 hour period is through. ACR also tends to compress the sleep portion of your daily cycle, causing you to lose valuable sleep. ACR sufferers often sleep less than 8 hours per night, and awaken early.
You may experience one or more of the following symptoms:
Because your daily cycle, or circadian rhythm is running fast, your pineal gland releases the nighttime hormone melatonin prematurely, causing you to feel tired earlier in the evening. Since melatonin is released prematurely, your body clock can't sustain a complete sleep cycle, and you awaken early. Because you don't receive the proper amount of sleep, your energy, alertness and ability to function may also be diminished.
Specialized bright light is the only effective treatment for ACR. Since bright light will suppress melatonin for approximately three hours, you should use bright light in the late afternoon and or evening while avoiding bright morning light before 9:00 am. If you need to be outside or in bright light before this time, you should wear sunglasses. Also, try to make your night time as dark as possible, and avoid using light when getting up during the night.
Circadian Amplitude Disorder (CAD means your body clock may be producing lower amounts of the night/day hormones during the day. If you have CAD, you may not have problems waking up or going to sleep, but the quality of the wakefulness and/or sleep is diminished. This means you'll probably have less energy during the day
You may notice one or more of the following symptoms:
Because your circadian rhythm is not as strong or pronounced as a normal circadian rhythm, your body is not receiving enough of the right hormones during the day. Your body receives enough of a signal to be able to sleep and wake up at the right time, but doesn't produce enough serotonin to be very active during the day, particularly during the evening hours. Also, your body clock doesn't produce enough melatonin to sustain a proper sleep cycle. CAD can also cause you to be less productive, and more susceptible to sickness.
CAD sufferers may not notice sleep problems but may experience energy and/or mood problems during the day. Although you may not notice sleep problems, you may not be getting refreshing sleep. If you experience a lack of energy or feel 'down' at times during the day, your sleep may be a factor.
While a normal circadian rhythm (daily activity cycle) runs through one sleep/wake cycle in 24 hours, a bimodal circadian rhythm tends to disrupt that cycle. BCR creates more than one low or sleep period, but the sleep periods may not be pronounced enough to allow sleep. Those with BCR tend to sleep for only a few hours each night, generally from about 2 am - 6 am or earlier. BCR may be one of the most common of circadian rhythm disorders among the elderly or indigent who do not receive consistent light/dark signals.
You may experience one or more of the following symptoms:
Because your daily cycle, or circadian rhythm is not operating properly, your pineal gland may be releasing the night time hormone melatonin during your day cycle, causing you to feel tired in the at various times during the day. Since melatonin is released prematurely, your body clock can't sustain a complete sleep cycle. You may experience a disrupted sleep and awaken early. You may also have difficulty falling asleep. Because you don't receive the proper amount of sleep, your energy, alertness and ability to function may also be diminished.
Specialized bright light (10,000 lux intensity) is the only effective treatment for BCR. Since bright light will suppress melatonin for approximately three hours, you should use bright light in the mid morning, afternoon, late afternoon and evening while avoiding bright morning light before 9:00 am. If you need to be outside or in bright light before this time, you should wear sunglasses.
Since BCR may cause you to be awake during the night, it is important to avoid light during the night. Even low levels of light such as a nightlight, can produce enough of a signal to adversely affect your circadian rhythm and prolong the BCR. Watching TV is acceptable, if no other lights are on, and you stay at least 8 feet from the TV. If you feel this is too restrictive, try using a lamp with a 20-watt or lower wattage bulb.
During the first ten days of shifting your circadian rhythm back to a normal pattern, you may benefit from taking time-release melatonin approximately two to three hours before your bedtime. Also, try to make your night time as dark as possible, and avoid using light when getting up during the night.
Since BCR or irregular sleep/wake cycles have severely disrupted circadian rhythms, it may be easier to use a new therapy to completely reset your circadian rhythm. Sleep Restriction retrains the body clock to allow sleep only during one cycle in the day. Sleep restriction involves bright light therapy and requires from 3 - 4 weeks to work, but those who have tried sleep restriction find their sleep improves at least 2 - 3 hours per night. For more information, see the section on sleep restriction in this web site.
Even though most people's body clocks run a bit slow or fast and can cause a circadian rhythm sleep disorder, they usually have enough of a light or dark signal sometime during the day that keeps their cycle from constantly shifting. However, a small number of people, and in particular 8 out of 10 blind people, have rhythms that constantly cycle at odd hours independent of a normal 24-hour day. This means that every now and then their rhythm is in sync, but most often it is not.
You may experience some of the following symptoms:
Because your daily cycle, or circadian rhythm does not recognize circadian light/dark cues, you are often awake when you want to sleep and vice versa. Once in a while you can find refreshing sleep for a few nights until your rhythm is again out of sync. A free running sleep/wake cycle causes a great deal of stress physically and mentally because your body's need to function is at odds with your rhythm. When you need to be active and energetic, your body is often producing the wrong withdrawal and sleep hormones. And when you need to sleep, you can't because your body is producing the active hormones and neurotransmitters. Those with Non 24-hour sleep/wake cycles feel as though they suffering from constant jet lag. Those who suffer from Non 24-hour sleep cycles and irregular sleep cycles are more prone to depression and other mood disorders.
For sighted people, bright morning light should regulate a free running circadian rhythm. If the rhythm is significantly out of sync, it may take a few weeks before the rhythm is regulated. In blind people, 3 - 5 milligrams of melatonin (time-release may be better) at 9 pm can help keep their rhythm in sync, although it is not as effective as bright light. When their cycle is closer to a normal 24-hour day, they only need to take .5 milligrams of melatonin at 9 pm.
It is also very important to provide as many circadian signals or zeitgebers as possible. Regular mealtimes, lower night time temperatures (8° lower) darker evening and dark nights, with very bright morning and daytime light are all helpful. Some studies show that morning bird sounds and high-density negative ionization also play a role in resetting the circadian rhythm.
Untreated disorders tend to become worse, not better. If you have a mild disorder, it may develop into moderate or acute one and become more difficult to control. If you have a circadian rhythm disorder, your body is likely producing melatonin at the wrong time of day, when you need to be active. Studies have linked this maladaptation to higher cancer risks. Circadian rhythm disorders may also contribute to stress and other health risks, since your body is not producing the hormones you need to be active, energetic. A recent nationwide study links higher mortality rates to insufficient sleep.
© 2005 Apollo Health, Inc. All rights reserved