Shift Work Type
Prevalence
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 advancement into middle-age and beyond (Drake et al. 2004).
Risk Factors
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 competing 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.
Diagnostic Features
Presence of both sets of symptoms are usually required for a diagnosis of shift work type:
Diagnosis is primarily based on a history of the individual working outside of the normal 8:00 A.M. to 6:00 P.M. daytime window (particularly at night) on a regularly scheduled (i.e., non-overtime) basis.
Symptoms of excessive sleepiness at work, and impaired sleep at home, on a persistent basis are prominent.
Typically, when the individual reverts to a daywork routine, symptoms resolve.
Although the etiology is slightly different, individuals who travel across many time zones on a very frequent basis may experience effects similar to those experienced by individuals with shift work type who work rotating shifts.