The prevalence of shift work type is unclear, but the disorder is estimated to affect 5%—10% of the night worker population (16%—20% of the workforce). Prevalence rises with advance- ment into middle-age and beyond (Drake et a1. 2004).
Shift work type can appear in individuals of any age but is more prevalent in individuals older than 50 years and typically worsens with the passage of time if the disruptive work hours persist. Although older adults may show similar rates of circadian phase adjust- ment to a change in routine as do younger adults, they appear to experience significantly more sleep disruption as a consequence of the circadian phase shift.
Temperamental. Predisposing factors include a morning-type disposition, a need for long (i.e., more than 8 hours) sleep durations in order to feel well rested, and strong com- peting social and domestic needs (e.g., parents of young children). Individuals who are able to commit to a nocturnal lifestyle, with few competing day-oriented demands, appear at lower risk for shift work type.
Genetic and physiological. Because shift workers are more likely than day workers to be obese, obstructive sleep apnea may be present and may exacerbate the symptoms.
A history and sleep diary or actigraphy may be useful in diagnosis, as discussed earlier for delayed sleep phase type.
Functional Consequences of Shift Work Type
Individuals with shift work type not only may perform poorly at work but also appear to be at risk for accidents both at work and on the drive home. They may also be at risk for poor mental health (e.g., alcohol use disorder, substance use disorder, depression) and physical health (e.g., gastrointestinal disorders, cardiovascular disease, diabetes, cancer).
Individuals with a history of bipolar disorder are particularly Vulnerable to shift work typebrelated episodes of mania resulting from missed nights of sleep. Shift work type of- ten results in interpersonal problems.
Normative variations in sleep with shift work. The diagnosis of shift work type, as op- posed to the ”normal” difficulties of shift work, must depend to some extent on the sever- ity of symptoms and / or level of distress experienced by the individual. Presence of shift work type symptoms even when the individual is able to live on a day-oriented routine for several weeks at a time may suggest the presence of other sleep disorders, such as sleep ap- nea, insomnia, and narcolepsy, which should be ruled out.
Shift work type has been associated with increased alcohol use disorder, other substance use disorders, and depression. A variety of physical health disorders (e.g., gastrointestinal disorders, cardiovascular disease, diabetes, cancer) have been found to be associated with prolonged exposure to shift work.
Relationship to International Classification of
The International Classification of Sleep Disorders, 2nd Edition (ICSD-Z), differentiates nine circadian rhythm sleep disorders, including jet lag type.
. Parasomnias
Parasomnias are disorders characterized by abnormal behavioral, experiential, or physio- logical events occurring in association with sleep, specific sleep stages, or sleep-wake tran— sitions. The most common parasomnias—non—rapid eye movement (NREM) sleep mixtures of wakefulness and NREM sleep and wakefulness and REM sleep, respectively.
These conditions serve as a reminder that sleep and wakefulness are not mutually exclu- sive and that sleep is not necessarily a global, whole-brain phenomenon.
A. Recurrent episodes of incomplete awakening from sleep, usually occurring during the first third of the major sleep episode, accompanied by either one of the following: 1. Sleepwalking: Repeated episodes of rising from bed during sleep and walking about. While sleepwalking, the individual has a blank, staring face; is relatively un- responsive to the efforts of others to communicate with him or her; and can be awakened only with great difficulty.