Circadian Rhythm Sleep-Wake Disorders 393
Advanced Sleep Phase Type
Specifiers 
Advanced sleep phase type may be document ed with the specified “familial.” Although
the prevalence of familial adva nced sleep phase type has no t been established, a family
history of advanced sleep phase is present in individuals with advanced sleep phase type.
In this type, specific mutations demonstrate an autosomal dominant mode of inheritance.
In the familial form, onset of symptoms ma y occur earlier (during childhood and early
adulthood), the course is persistent, and the se verity of symptoms may increase with age.
Diagnostic Features
Advanced sleep phase type is characterized by sleep-wake times that are several hours
earlier than desired or conventional times. Di agnosis is based primarily on a history of an
advance in the timing of the major sleep period  (usually more than 2 hours) in relation to
the desired sleep and wake-up time, with sy mptoms of early morning insomnia and ex-
cessive daytime sleepiness. When allowed to  set their schedule, individuals with ad-
vanced sleep phase type will exhibit norm al sleep quality and duration for age. 
Associated Features Supporting Diagnosis
Individuals with advanced sleep phase type are “morning types,” having earlier sleep-
wake times, with the timing of circadian biom arkers such as melatonin and core body tem-
perature rhythms occurring 2–4 hours earlier th an normal. When required to keep a con-
ventional schedule requiring a delay of bedtim e, these individuals will continue to have an
early rise time, leading to persistent sleep de privation and daytime sleepiness. Use of hyp-
notics or alcohol to combat sleep-maintenance insomnia and stimulants to reduce daytime
sleepiness may lead to substance abuse in these individuals. 
Prevalence