Delayed Sleep Phase

Delayed sleep phase syndrome (DSPS) is a condition that affects your ability to fall asleep and wake up on time. The delay in your sleep schedule is off by at least two hours. This condition affects your internal clock.

As an example, rather than falling asleep at 10 p.m. and waking at 6:30 a.m., a person with delayed sleep phase syndrome will fall asleep well after midnight and have trouble getting up in time. If they were to keep a sleep diary, it would show short sleep periods during the school or work week (with few or no awakenings during the night) and lengthy sleep-ins (late morning to midafternoon wake-up times) on the weekend.

Most people with DSPS describe themselves as “a night owl“ or an evening person, but they’re not. If you have DSPS, you’re not able to regulate when your body tells you to fall asleep. If you’re a night owl, you don’t have severe daytime dysfunction (daytime sleepiness) as seen with DSPS.

You may hear your healthcare provider call this condition delayed sleep phase syndrome or delayed sleep-wake phase disorder.

What kind of sleep disorder is delayed sleep phase syndrome?

Delayed sleep phase syndrome is a type of sleep disorder called a circadian rhythm sleep disorder. Your circadian rhythm is a 24-hour cycle that helps you stay awake during the day and fall asleep at night. This cycle regulates how certain parts of your body function, like your body temperature and digestion.

What are the types of delayed sleep phase syndrome?

There are two types of delayed sleep phase syndrome characterized by when the sleep hormone (melatonin) signals your circadian rhythm. This signal (onset) tells your internal clock that it’s time to go to sleep:

• Circadian aligned: The melatonin onset is less than two hours before you fall asleep.
• Circadian misaligned: The melatonin onset is more than two hours before you fall asleep or it doesn’t happen until after sleep begins.