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New findings bring mixed blessings to those looking to combat jet lag


Jet lag occurs when we travel across multiple time zones by air. Anyone who has experienced jet lag knows that it causes sleep disturbances and daytime sleepiness, and can impair performance after landing. A team of researchers has investigated the effects of slow release caffeine (SRC) and melatonin (Mlt) on recovery sleep and daytime sleepiness after a seven-time zone eastbound flight and found that both drugs have positive effects on some jet lag symptoms after an eastbound flight. They found that SRC alleviates daytime sleepiness but exerts some unwanted effects on sleep. By contrast, Mlt was found to improve sleep but did not objectively mitigate sleepiness.

This study is part of a large, real-world French-American study called "Operation Pegasus" in which some 140 physiological, psychological, and biological parameters are measured. These results may be part of a larger plan for travelers looking to fine-tune for freshness after a long-haul flight.

A New Study

The new study is entitled "Caffeine Or Melatonin Effects On Sleep and Sleepiness After Rapid Eastward Transmeridian Travel." The authors of the study are M. Beaumont, D. Bate´jat, C. Pie´rard, P. Van Beers, and O. Coste, of the Department of Physiology, Institut de Me´decine Ae´rospatiale du Service de Sante´ des Arme´es, Bre´tigny sur Orge, France; J. B. Denis, and P. Doireau, from the Centre Principal d’Expertise Me´dicale du Personnel Navigant, Clamart, France; F. Chauffard of Nestec SA, Nestle´ Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland; J. French, Air Force Research Laboratory, Brooks Air Force Base, San Antonio, TX; and D. Lagarde, Direction Centrale du Service de Sante´ des Arme´es, Arme´es, France. Their findings appear in the January 2004 edition of the Journal of Applied Physiology, one of 14 scientific journals published monthly by the American Physiological Society (APS) (


The researchers used the following methodology:

The double-blind, randomized, placebo (Pbo)-controlled study was conducted on 27 health volunteers from a US Air Force Reserve Unit that was representative of the US population. Questionnaires showed that the volunteers were neither morning nor evening types, habitually went to bed between 2300 and 2400 h, and had a sleep duration of 6.5-7.5 hours. They were nonsmokers who did not consume large amounts of xanthine-based beverages on a regular basis (coffee, tea, and cola: equivalent to <3 cups/day).

Experimental Protocol:
The subjects were housed and trained at Brooks Air Force Base in San Antonio, TX over 6 days and their routines were identical. During the first 5 days, they were familiarized with the procedures, tests and measurements. Baseline data were obtained during the last night (N-1) and day (D-1). The flight was scheduled on Day 0 (D0) at 1500 (US time) for a seven-time-zone eastbound flight to France. Subjects were prohibited from sleeping during the flight so that they were awake 33 h from last awakening in Texas to first sleep in France. The arrival was on D1 and recovery lasted 10 days (D1-D10) and 9 nights (N1-N9). During the days the subjects followed a rigorous course of activities involving cognitive and physical performance testing. The subjects were randomly assigned into three parallel groups, each containing 3 women and 6 men to be administered either 300 mg of SRC, 5 mg Mlt, or Pbo. SRC (300 mg) was administered from D1 to D5 at 800 mg; 5 mg synthetic Mlt on D-1, D0, and from D1 to D3; and Pbo in the same schedule. The Mlt intake schedule corresponded before, during, and after the flight, to bedtime in France.

Baseline and recovery sleep patterns ("architecture") were assessed from electroencephalography (EEG) and other standard methods. Qualitative and quantitative aspects of sleep were evaluated from sleep logs completed after wake-up from D1 to D10. Sleepiness was assessed from EEG recordings over baseline and recovery periods.

Statistical Analysis:
Sleep and sleepiness data were analyzed separately and compared by two-way ANOVA (drug: SRC, Mlt, Pbo; period of time: recovery vs. baseline) with repeated measurements over time. The level of significance (P) was set at 0.05.


The following observations were made:

In recovery sleep, the researchers observed only a few significant differences between drug conditions with each night. Sleep logs also identified few differences between the drug groups on any given night.

For daytime sleepiness, SRC subject were not sleepy during the period that the drug was given (D1-D5) except on D1 and D2 PM, when sleep latencies were reduced. However, sleep latencies were higher under SRC than under Pbo on D1 PM and D2 AM. This stimulating effect, compared with Pbo, tended to be maintained until D6. Thereafter, compared with baseline, SRC subjects were sleepier from D6, i.e., at the end of the treatment. Under Mlt, the subjects were sleepier than in the baseline condition over the entire recovery period during which the drug was taken. Subsequently, sleep latencies did not differ from baseline on D4-D5, decreased again until D8 AM, and returned to baseline level until D10 AM.

For subjective measures of sleepiness, there was no significant difference among the three drug groups regarding awake/sleep except on D1 AM, when SRC subjects were sleepier than the Mlt group. No significant differences were observed among the three drug groups within each day of the study, except for the Mlt subjects, who felt less sleepy during the flight than did the two other groups who had not taken any active drug. Mlt subjects were also less sleepy than SRC subjects on D1 AM.


Accordingly, the researchers conclude:
  • that SRC and Mlt may be of value in alleviating some symptoms related to eastbound jet lag combined with sleep deprivation;

  • Mlt decreased sleepiness subjectively but not objectively, and improved recovery sleep; and

  • SRC’s most notable effect was to reduce sleepiness for a few days with some unwanted effects on recovery sleep.

Additional studies are required to evaluate fully the effects of these SRC and Mlt on recovery sleep and sleepiness after an eastbound flight.

The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

Donna Krupa | EurekAlert!
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