DENVER – With the right combination of morning bright light exposure, low-dose melatonin, and gradually advancing bedtimes in the days prior to flying eastward, travelers can avoid the hassles of jet lag, Victoria L. Revell, Ph.D., said at the annual meeting of the Associated Professional Sleep Societies.
“With a little bit of preparation you can arrive with no jet lag, and not waste any days, and be more productive at your meeting, and enjoy your trip,” added her coinvestigator, Charmane I. Eastman, Ph.D., professor of psychology and director of the Biological Rhythms Research Laboratory at Rush University Medical Center, Chicago.
The investigators explained that jet lag is the result of misalignment between circadian rhythms and the destination time zone. It is worse after flights eastward because people find it more difficult to phase advance than phase delay. The purpose of pretrip re-entrainment is to help travelers, once they arrive at their destination, keep their circadian temperature drop where it belongs: during the night, when they're sleeping.
“People think, 'Oh, if only I could sleep at night; I'll just take a sleeping pill.' But that only solves half the problem because if you do that to sleep, you'll still feel bad during the day walking around out of phase with your temperature minimum,” Dr. Eastman added.
The program developed by the Chicago investigators involves four 30-minute light-box sessions in the morning, alternating with 30 minutes of ordinary room light. The first session begins upon awakening. The single light box emits about 5,000 lux using cool white fluorescent lamps. A light box is used because it's convenient; bright morning sunlight isn't available every day. The alternating 30-minute bright-light/room-light sessions are, once again, a matter of convenience.
It's possible, for example, to fit in one light box session while reading the morning paper, then go take a shower, then return to the light box while eating breakfast, then go get dressed before having another light session while working at the computer.
Bedtime is moved 1 hour earlier each evening for the same number of days as time zones to be crossed. Melatonin at a dose of 0.5 mg is taken roughly 5 hours before bedtime, which prior sleep lab work has established as the optimal time to take the hormone in order to induce phase advances. The melatonin enhances the size of the daily phase advance, thereby cutting down on the number of days a traveler needs to follow the program.
The investigators reported on 44 healthy volunteers who participated in a blinded three-night sleep lab study that established 0.5 mg as the optimal melatonin dose. Each morning the participants received four intermittent 30-minute sessions of bright light. Each night they went to bed 1 hour earlier than the night before. And each afternoon they took 0.5 or 3.0 mg of melatonin or placebo.
The mean phase advance was determined by dim-light melatonin onset measured via saliva samples. (See box.)
To ensure that the phase advancement wasn't causing jet lag-type symptoms, participants completed the Columbia Jet Lag Scale daily and the Stanford Sleepiness Scale five times per day.
The results were reassuring except that subjects on 3.0 mg/day of melatonin reported a slight increase in daytime sleepiness. It wasn't enough to pose a safety hazard, but since the efficacy wasn't significantly greater than with 0.5 mg/day, the investigators decided low-dose therapy was the way to go, Dr. Revell explained.
Outside of the controlled laboratory setting, Dr. Eastman said she and numerous friends and colleagues have employed the phase-shift travel preparation method with great success.
The study was supported by the National Institutes of Health. Melatonin and matching placebos were provided by Ecological Formulas.
