Circadian Rhythm Sleep Disorders A subset of patients presenting with either insomnia or hypersomnia may have a disorder of sleep timing rather than sleep generation. Disorders of sleep timing can be either organic (., due to an intrinsic defect in the circadian pacemaker or its input from entraining stimuli) or environmental (., due to a disruption of exposure to entraining stimuli from the environment). Regardless of etiology, the symptoms reflect the influence of the underlying circadian pacemaker on sleep-wake function. Thus, effective therapeutic approaches should aim to entrain the oscillator at an appropriate phase. Jet Lag Disorder More than 60 million persons. | Chapter 028. Sleep Disorders Part 13 Circadian Rhythm Sleep Disorders A subset of patients presenting with either insomnia or hypersomnia may have a disorder of sleep timing rather than sleep generation. Disorders of sleep timing can be either organic . due to an intrinsic defect in the circadian pacemaker or its input from entraining stimuli or environmental . due to a disruption of exposure to entraining stimuli from the environment . Regardless of etiology the symptoms reflect the influence of the underlying circadian pacemaker on sleep-wake function. Thus effective therapeutic approaches should aim to entrain the oscillator at an appropriate phase. Jet Lag Disorder More than 60 million persons experience transmeridian air travel annually which is often associated with excessive daytime sleepiness sleep onset insomnia and frequent arousals from sleep particularly in the latter half of the night. Gastrointestinal discomfort is common. The syndrome is transient typically lasting 2-14 d depending on the number of time zones crossed the direction of travel and the traveler s age and phase-shifting capacity. Travelers who spend more time outdoors reportedly adapt more quickly than those who remain in hotel rooms presumably due to bright outdoor light exposure. Avoidance of antecedent sleep loss and obtaining nap sleep on the afternoon prior to overnight travel greatly reduces the difficulty of extended wakefulness. Laboratory studies suggest that sub-milligram doses of the pineal hormone melatonin can enhance sleep efficiency but only if taken when endogenous melatonin concentrations are low . during biologic daytime and that melatonin may induce phase shifts in human rhythms. A large-scale clinical trial evaluating the safety and efficacy of melatonin as a treatment for jet lag disorder and other circadian sleep disorders is needed. Shift-Work Disorder More than 7 million workers in the United States regularly work at night either on a permanent or rotating
