Disorders that are related to changes in the normal sleep-wake pattern include:
- Advanced Sleep-Phase - 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 pm. Waking time often occurs between 1 and 3 am.
- Delayed Sleep-Phase - The usual nighttime sleep period occurs later than the desired bedtime. These "night owls" are unable to sleep until the early morning hours. They don't arise until late morning to early afternoon.
- 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 are erratic. Evening insomnia and daytime sleepiness are common symptoms.
- 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, westward flights result 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.
- Shift Work Sleep Disorder - Large numbers of people in this country perform shift work. Excessive sleepiness and insomnia may develop when people work outside the 8am to 5pm shift. Sleepiness and decreased concentration is common if one must work at night. A shift work sleep disorder poses a major hazard in the workplace.