Circadian Rhythm Disorders
Circadian rhythm sleep disorders (CRSD) are a family of sleep disorders affecting the timing of sleep. Circadian rhythm is the name given to your body’s 24-hour “internal clock.” This internal clock controls your body’s sleep-wake cycle.
Helping to “set your internal clock” during a 24-hour day is the visual cue of light – specifically, its brightness / type of light, amount of time exposed to light, and when exposed to light.
If you suffer from a circadian rhythm sleep disorder, you may not be able to sleep and wake at the times required for normal work, school and social needs. If you are allowed to sleep and wake at the times dictated by your own body clock, you are generally able to get enough sleep.
Sleep is usually of normal quality unless there is another sleep disorder present.
There 6 CRSDs.
Delayed Sleep Phase Disorder (DSPD)
DSPD, often known as ‘night owls’ .This is characterised by an inability to fall asleep until 2-6 hours after usual sleep onset times (10pm to midnight) resulting in extreme difficulty with waking. When left to sleep, sleep length is generally normal or extended. DSPD has a prevalence of 7-16% in adolescents and young adults. Daytime functioning can be severely impaired by DSP. It can lead to excessive sleepiness and fatigue.
Advanced sleep-wake phase disorder (ASP)
People with ASP have an “early bird” circadian clock. They fall asleep several hours before a normal bedtime. As a result, they also wake up hours earlier than most people wake in the morning.
People with ASP feel sleepy in the late afternoon. Bedtime tends to occur between 6 p.m. and 9 p.m. Since bedtime is early, they also wake up early. They tend to wake up between 2 a.m. and 5 a.m. While the timing of sleep is early, sleep itself is normal.
Advanced sleep phase syndrome can affect both men and women equally but is more common in the elderly. Roughly 1% of people middle aged or older experience ASPS.
Non-24-Hour Sleep-Wake Syndrome
People who have non-24-hour sleep-wake syndrome (aka free running disorder) have a circadian rhythm that is out of sync. It causes these people to have slightly longer than 24-hour sleep cycles and causes their body clock to shift to later bedtimes every couple of days, making them go to sleep and rise at later times each day.
Non-24 hour sleep-wake syndrome is most common in blind people. As they are unable to regulate patterns of light and dark, therefore allowing the circadian rhythm to run free.
It is believed that as many as half of totally blind people suffer from the disorder. The disorder is less understood in sighted people suffering from non-24 hour sleep-wake syndrome.
Irregular Sleep-Wake Rhythm
This circadian rhythm sleep disorder occurs in people who have sleep-wake cycles that are not defined by any typical patterns of sleep. Instead, their sleep occurs as various "naps" throughout a 24-hour period that usually adds up to a normal sleep cycle of 7-9 hours. For these people there is no regular pattern and their nap times and durations can vary on a day-to-day basis.
Many sufferers of irregular sleep-wake rhythm complain of insomnia (because they can't sleep normally at night), excessive daytime sleepiness (because they feel the need to nap during the day), or both.
This circadian sleep rhythm disorder is extremely rare but is more prevalent in sufferers who have other medical or mental disorders such as dementia, brain damage, and mental retardation.
Shift-work sleep disorder
This occurs when a person's circadian rhythm conflicts with their work schedule causing them to experience insomnia or excessive daytime sleepiness. Shift-work is characterized by working hours outside of the traditional 9 a.m. to 5 a.m. schedule. It includes the early morning shift, late evening shift, the night shift, and rotating work schedules. Many people with set schedules such as early morning shifts and night shifts can adapt to their schedule if it is regular. However, people who work rotating schedules are at most risk as not having a regular schedule can wreak havoc on their circadian rhythm.
Jet Lag
Jet Lag occurs when a person quickly travels by plane to a new time zone, often one that is a few hours off from their home location. Jet leg most often occurs 2 time zones away from home. At the new location the person has to adjust to a new sleep-wake cycle that is at odds with their circadian rhythm. Jet lag is often harder to adjust to during eastward travel, as the new schedule requires earlier awakenings rather than later ones.
Jet lag is often a temporary disorder and the new time zone can be adapted to within a few days. However, jet lag disorder can be more serious for frequent fliers whose jobs require constant travel. Jet lag is often more difficult for the elderly to adapt to than the young.
Diagnosis
Keeping a diary of your sleep, including bed wake times is a useful way of tracking sleep patterns. Your GP may refer to the Sleep service.
An overnight sleep study is not usually required, however movement can be monitor using a special type of wrist watch, called an ActiWatch. This is usually worn for a 3 week period alongside a sleep diary. This will show the specialist if there are patterns of movement and when they occur.
Treatments
Behaviour Therapy
Depending on the circadian rhythm disorder, certain behavioural or lifestyle remedies may help alleviate symptoms of the disorder.
- Maintaining regular sleep-wake times
- Avoiding naps
- Getting regular exercise
- Avoiding caffeine and nicotine before bed
- Adjusting exposure to daylight. Those with delayed sleep phase syndrome should minimize exposure to electronics that mimic daylight (laptops, TV’s, cell phones, portable game consoles, etc.) and those with advanced sleep phase syndrome should increase light exposure in the evenings.
Bright Light Therapy
Light therapy can be used to help advance or delay sleep through the use of a high intensity lightbox. Bright light therapy helps in calibrating the circadian rhythm by having the user sit in front of the bright light box at appropriate times of the day (depending on the disorder being treated) for a varied amount of time (depending on doctor recommendations).
Medications
Certain medications may be prescribed depending on the type of disorder. Wake promoting agents or sleeping aids may be prescribed.
Melatonin, the hormone that helps regulate sleep, may be prescribed to be taken at certain times to help reset your internal body clock.