Study objectives: To determine whether appropriately timed administration of a short-acting benzodiazepine hypnotic, which has proven effective in an animal model of jet lag, also facilitates adaptation of circadian rhythmicity and sleep-wake homeostasis in a human model of jet lag.
Design: Subjects participated in two double-blind, placebo-controlled studies of adaptation to an 8-hr delay shift of sleep-wake and dark-light cycles simulating westward travel. Each 9-day laboratory study began with a 3-day habituation period followed by a 24-hr study to obtain basal hormonal and sleep profiles (23:00-07:00). Subjects were then kept awake until 07:00 the next day and slept in darkness 07:00-15:00 for the next five 24-hr spans post-shift.
Participants: 6 normal, healthy men 24-31 years of age.
Interventions: Oral Triazolam (0.5 mg) or placebo given at 04:00 before the first shifted sleep/dark period (3 hours before bedtime) and at 07:00 (at bedtime) on days 2-5 post-shift.
Measurements and results: Sleep recordings and 24-hr cortisol and growth hormone profiles were obtained at baseline and on the first, third, and fifth days post-shift. Global measures of treatment efficacy were calculated for multiple endpoints representing circadian rhythmicity and sleep-wake homeostasis. With placebo, the shift induced disturbances of sleep and hormonal secretion, and a gradual re-entrainment of circadian rhythmicity. Triazolam significantly facilitated adaptation by accelerating re-entrainment of circadian rhythms (chronobiotic effect) and normalizing markers of sleep/wake homeostasis (hypnotic effect).
Conclusions: Appropriately timed administration of a benzodiazepine hypnotic appears to facilitate the adaptation of both circadian rhythmicity and sleep-wake homeostasis to a shifted dark/sleep cycle. Compounds with combined chronobiotic/hypnotic properties may be useful in conditions of jet lag or night work.