Delayed sleep phase syndrome (DSPS), also called phase lag syndrome, is a circadian rhythm sleep disorder. However, unlike jet lag and the effects of shift work, delayed sleep phase syndrome is a persistent condition. In clinical settings, DSPS is one of the most common complications of sleep-wake patterns.
Delayed sleep phase syndrome results when the patient's internal biological clock does not match his or her external environment (called desynchronization). Unlike jet lag, this desynchronization is not activated by travel or a change in external environment. Rather, the patient's propensity to fall asleep is simply "delayed" in relation to other people's. Subsequently, a patient with DSPS is desynchronized with the routine that governs most of his or her life.
Patients with delayed sleep phase syndrome typically are unable to fall asleep before 2 a.m. and have extreme difficulty waking early (e.g., by 7 a.m.). People who have DSPS are sometimes called "night owls" or are described as not being "morning people." If they are able to sleep a full 7 to 8 hours (e.g., until 10 a.m.), they feel rested and function normally. Unfortunately, this is usually not the case.
The main difficulty for patients with DSPS is functioning early in the morning for school or work. A person with DSPS often fails courses in school or loses jobs, which can compromise their health and well-being and can have social and financial implications.
Patients with DSPS may initially refer to their symptoms as insomnia. As soon as people deviate from a normal sleep pattern, they tend to assume that they are not capable of sleep at all, but this is not true. Patients with DSPS are able to get plentiful sleep; it just differs from traditional sleep-wake patterns. DSPS makes it hard to wake up in the morning when simultaneously indulging in a late night sleep routine.
Incidence and Prevalence Incidence of delayed sleep phase syndrome is unknown. In a recent study involving 5000 participants, DSPS accounted for about 40% of disorders involving sleep-wake schedules. DSPS may surface in childhood and it occurs most often in young men. It is estimated that the disorder affects approximately 7% of teenagers.