Melatonin helps travelers prepare for long-haul
for several days before crossing time zones can help travelers
avoid jet lag by resetting their Circadian rhythms, and may also be
of use to sufferers of delayed sleep phase syndrome.
Melatonin is a natural, soporific hormone secreted by the pineal gland during the hours of darkness. Melatonin supplements are widely available in the United States and are reported to induce sleep and ameliorate disturbed sleep patterns - both intrinsic and due to extraneous circumstances such as shift work or jet-lag.
The researchers from Rush University Medical Center in Chicago previously showed that advancing the sleep schedule by one hour a day and administering bright light upon waking could advance the human Circadian clock (24-hour sleep cycle) by about 30 minutes per day.
In the current study, published in the advance online edition of the Journal of Clincal Endocrinology and Metabolism, they set out to see whether taking melatonin in the afternoon could increase the effect.
The study involved 44 healthy adults aged between 19 and 45 years. For the first six days they were assigned a strict eight-hour sleep schedule, during which time they had to remain in the dark, trying to sleep.
On the seventh day, their Circadian phases were assessed, starting seven hours before their bedtime and ending three hours after the start of their bedtime. They continued on this schedule until day ten, when intervention began.
Over the next three days, the participants slept in the lab in individual dark, temperature-controlled rooms, and their sleep/dark schedule was advanced by one hour a day. In the afternoons they received either 0.5 mg or 3.0 mg of melatonin, or a placebo, timed so as to produce the maximal possible phase advance (seven hours prior to bedtime for 3.0mg and five hours for 0.5mg).
On the 14th day, the researchers found that the phase advances were larger in those receiving melatonin - 2.6 hours for the 3.0mg group and 2.5 hours for the 0.5 mg, compared to 1.7 for the placebo group. The participants experienced no jet lag-type symptoms.
The effect of taking the melatonin in combination with the light box therefore advanced Circadian rhythms by about 50 minutes per day.
Since those taking the 3.0 of melatonin reported feeling sleepy in the evenings, and the phase advancement was not significantly greater with this dose, the researchers recommend 0.5 mg of melatonin as the optimum dose.
Interestingly, a study published in the Journal of Clinical Endocrinology and Metabolism in October 2001, showed that only around 0.3mg of melatonin is needed to help adults fall asleep and return to sleep after waking up during the night.
Lead author Richard Wurtman of the Massachusetts Institute of Technology maintains that a higher dose taken over several days can actually block the beneficial effects, as the brain's melatonin receptors become unresponsive when exposed to excess quantities, and cause some people to experience hangover-like symptoms during the day.
According to lead researcher of the Rush study Dr Charmane Eastman, director of the biological rhythms research lab and professor of the behavioral sciences department, the new findings provide business travelers with a method to avoid jet lag prior to flight, since melatonin can be purchased over-the-counter in the United States and light boxes for home use are relatively easily rented or purchased.
"If they did this for the number of days equivalent to the number of time zones crossed, then they should be completely adjusted to the new time zone before they fly," she said.
"However, even following the schedule for a few days before flying would reduce the jet lag experienced upon arrival at the destination. The more days a person follows this procedure the less jet lag they will have on landing and the sooner they will adjust and feel no jet lag."
Melatonin is not presently available as a supplement in Europe, Australia and a number of other countries, where it is regulated as a medicine.
