Circadian Rhythm Sleep Disorders: Types

Disorders that are related to changes in the normal sleep-wake pattern include:

• Advanced Sleep Phase Disorder: Often referred to as “early birds.” This is a shift in nighttime sleep to a time earlier than the desired bedtime. Arising time the next morning is also earlier than desired. Bedtime often occurs between 6 and 9 p.m. Waking time often occurs between 1 and 3 a.m. People with this disorder often find it difficult to stay awake in the later evening.

• Delayed Sleep Phase Disorder: Often referred to as “night owls.” The usual nighttime sleep period occurs later than the desired bedtime. People with this disorder are often unable to fall asleep until the early morning hours. They don't arise until late morning to early afternoon. A typical bedtime may be between 2 and 4 a.m., with a waking time of around noon. They frequently complain of difficulty waking up in the morning.

• Irregular Sleep-Wake Pattern - Sleep and wake times are disordered. Three or more naps replace the major nighttime sleep. The timing of sleep and wake activities is erratic. Evening insomnia and daytime sleepiness are common symptoms.

• Shift Work Sleep Disorder: Large numbers of people in this country perform shift work. Excessive sleepiness and/or insomnia may develop when people work outside the 8 a.m. to 5 p.m. shift. Sleepiness and decreased concentration are common if one must work at night. A shift work sleep disorder poses a major hazard in the workplace.

• Jet Lag: After rapid travel across many time zones, our internal clock remains fixed to our home time zone. It may take a few days for the internal clock to adjust to the new time zone. For example, the earlier bedtime after an eastward flight may result in trouble falling asleep at a ‘normal time.’ On the other hand, a westward flight results in a delay in nighttime sleep. It also results in increased awakenings during the early morning hours. Luckily for the traveler, sleep tends to improve after two to three days.