Circadian Rhythm Sleep Disorders (CRSD) are a group of sleep disorders that affect the timing of sleep. Circadian Rhythm is the natural sleep-wake cycle of the human body. When a person has CRSD, they are unable to sleep and wake during normal sleeping and waking hours. Most of the time people with CRSD are unable to cope with the sleep and wake times required for them to properly function on their work or school.
CRSD fall under two basic categories: Intrinsic and Extrinsic. When a person has Intrinsic Disorders, the person’s biological clock is not in alignment with what the rest of society follows. A person can be going to sleep or rising later than usual. They can also be going to sleep or rising at earlier times.
With Extrinsic Disorders, a person’s sleep-wake cycle is aligned with the normal light and darkness patterns. However, their biological clock gets disrupted by their uncommon schedules. The source of this uncommon schedule may be their schoolwork, travels, or occupational demands.
Advanced Sleep Phase Disorder (ASPD)
It is also known as Advanced Sleep Phase Syndrome (ASPS). This is a disorder wherein a person falls asleep a few hours before the normal bedtime and wakes up several hours earlier than most people.
Delayed Sleep Phase Disorder (DSPD)
This is a sleep disorder that is the opposite of ASPD. With DSPD, a person’s sleep pattern gets delayed. A person with DSPD has a much later than normal onset and offset of sleep. This means that they go to sleep later at night. As a consequence, they wake several hours later in the morning. Those with SDPD feel excessively sleepy during the first part of the day.
Irregular Sleep-Wake Rhythm
Those who suffer from this disorder have disorganized Circadian Rhythms. They do not have a clear sleep or wake pattern. When a person has this disorder, they may sleep off and on during the night and take several naps during the day.
Non-24-hour Sleep-Wake Disorder
This disorder is also called Hypernychthemeral Syndrome. In this disorder, a person’s sleep time adjusts later and later each day. This means that the waking time and period of alertness also adjust thus affecting the person’s job or personal life.
Shift Work Sleep Disorder
A person experiences this disorder if his work schedule conflicts with his Circadian Rhythm. This usually happens when the patient’s job requires him to work outside of the traditional 9 AM to 5 PM work schedule.
A person experiences jet lag when he quickly crosses time zones. This happens when a person travels by plane to a location that is 2 time zones away from his home.