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Phase-Dependent Effect of Room Light Exposure in a 5-h Advance of the Sleep-Wake Cycle: Implications for Jet LagCenter for Study and Treatment of Circadian Rhythms, Douglas Hospital, Department of Psychiatry, McGill University, Montreal, Quebec, Canada; 6875 LaSalle Boulevard, Verdun, Quebec H4H 1R3, Canada; e-mail: boidia{at}douglas.mcgill.ca
Center for Study and Treatment of Circadian Rhythms, Douglas Hospital, Department of Psychiatry, McGill University, Montreal, Quebec, Canada The acute disruption in sleep quality, vigilance levels, and cognitive and athletic performance observed after transmeridian flights is presumed to be the result of a transient misalignment between the endogenous circadian pacemaker and the shifted sleep schedule. Several laboratory and field experiments have demonstrated that exposure to bright artificial light can accelerate circadian entrainment to a shifted sleep-wake schedule. In the present study, the authors investigated whether the schedule of exposure to indoor room light, to which urban dwellers are typically exposed, can substantially affect circadian adaptation to a simulated eastward voyage. We enrolled 15 healthy young men in a laboratory simulation of a Montreal-to-London voyage. Subjects were exposed to 6 h of room light (mean ± SD: 379 ± 10) prior to bedtime (n = 7) or when on a progressively advancing schedule (n = 8) early in the day. The remaining 10 hours of wakefulness were spent in dim light (4 ± 1 lux). Circadian assessments, performed via the constant routine procedure, evaluated the phase of the endogenous circadian rhythms of core body temperature and plasma melatonin before and after 1 week on the shifted schedule. At the end of the study, only subjects exposed to room light on the advancing schedule expressed oscillations of the endogenous circadian pacemaker in phase with the new sleep-wake cycle. In this group, a mean advance shift of the nadir of core body temperature of +5:22 ± 0:15 h was observed, with parallel shifts in plasma melatonin concentration and subjective alertness. The circadian rhythms of subjects exposed to room light later in the day remained much more adjusted to the departure than to the destination time zone. These results demonstrate that the schedule of exposure to room light can substantially affect circadian adaptation to a shifted sleep-wake schedule.
Key Words: human circadian rhythms • circadian reentrainment • phototherapy • indoor room light • subjective alertness • plasma melatonin • jet lag • transmeridian travel
Journal of Biological Rhythms, Vol. 17, No. 3,
266-276 (2002) This article has been cited by other articles:
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