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. 2009 Jun 1;4(2):241-255.
doi: 10.1016/j.jsmc.2009.02.006.

How To Travel the World Without Jet lag

Charmane I Eastman  1 , Helen J Burgess
Affiliations

How To Travel the World Without Jet lag

Charmane I Eastman et al. Sleep Med Clin. .
No abstract available

PubMed Disclaimer

Figures

Figure 1
Figure 1
Diagram showing a round trip flight from San Francisco to Beijing, China across 9 time zones. The rectangle on days 0–1 shows the time of the flight from San Francisco to Beijing (westward flight) and the rectangle on day 9 shows the return flight (eastward). The time lines on the top show the time in San Francisco (in daylight savings time) and the time lines on the bottom show the equivalent time in Beijing. The yellow horizontal bars show the maximum duration of the photoperiod (at the summer solstice) and the vertical lines within the bars show the minimum duration of the photoperiod (at the winter solstice). In bed times (dark) are represented by the 2 dots connected by a line. This schedule shows what might happen to a traveler, who we’ll call Henry, who usually sleeps from 11:30 pm to 7:00 am and maintains that schedule while in Beijing. The triangle represents the temperature minimum (Tmin), a marker for the phase of the circadian clock, the sleepiest circadian time, and a rough marker for the crossover point from phase delays to phase advances in the light PRC. The Tmin phase delays by 1.5 h/day after landing in Beijing until the original phase position of 4:00 am is reached on day 6. After the return flight east (a phase advance of zeitgebers) two possibilities for re-entrainment are shown, a phase delay of 1.5 h/day (antidromic re-entrainment shown by the open triangles) and a phase advance of 1 h/day (orthodromic re-entrainment shown by the filled triangles). These are the classic averages for phase shifts after flights by Aschoff et al [22] but will be altered by the actual pattern of light and dark to which Henry is exposed. The Tmin quickly reaches the time for sleep after the trip west, so Henry should have very few days of jet lag. In contrast, after the return trip east it takes a long time for the Tmin to reach sleep regardless of the direction of re-entrainment. The day of the week listed on the left and right sides change at midnight, which is 9 h later in the bottom time lines compared to the top. On the days of the flights, it appears that Henry “gains” or “loses” a day (compare the day of the week on the left to that on the right), because he crosses the International Date Line twice. In reality there are still 24 h in a day. For the purposes of our descriptions, day numbers refer to the rows shown and do not change at midnight.
Figure 2
Figure 2
Phase response curves (PRCs) generated from subjects free-running through an ultradian LD cycle (LD 2.5:1.5) for three 24 h days. Melatonin pills (3.0 mg) or bright light pulses (2 h of ~ 3500 lux) were given each day, with different subjects receiving the zeitgeber at different times of day. Phase shifts were derived from circadian phase assessments conducted before and after the 3 days of free-running. The x-axis shows the time the pill was given or the time the bright light pulse began relative to each subject’s DLMO, represented by zero on the bottom time line and the upward arrow. For convenience we added a clock time axis for a subject with a DLMO of 21:00, a rectangle showing a typical entrained sleep time (starting 2.5 h after the DLMO and lasting for 7.5 h) and a triangle 7 h after the DLMO showing the typical time of the temperature minimum (Tmin). The melatonin PRC is a curve fit to 27 points (27 subjects), and the data points can be seen in Burgess et al [82]. The bright light PRC should be considered preliminary because there were only 7 points (7 subjects). The dashed sections correspond to times with no data points. This preliminary light PRC can also be seen in Revell & Eastman [1]. The 2.5 h interval from the DLMO to sleep onset was based on averages from our laboratory studies [83, 84].
Figure 3
Figure 3
The melatonin PRC to 3.0 mg from Figure 2 and a melatonin PRC to 0.5 mg. The curve for 0.5 mg was fit to the data of Lewy et al. The human phase response curve (PRC) to melatonin is about 12 hours out of phase with the PRC to light. Chronobiol Int 1998; 15: 71–83. Note the different y-axes for the different doses. This is probably not due to the difference in dose, but rather to the difference in protocols, i.e., free-running subjects for 3.0 mg and entrained subjects for 0.5 mg. These PRCs show that the 3.0 mg dose needs to be taken earlier than the 0.5 mg dose to produce the maximum phase advance.
Figure 4
Figure 4
The same flight schedule as in Figure 1, but in this case Henry gradually changes the time of his sleep episodes (dark), controls light exposure and takes melatonin to phase shift his circadian clock and avoid circadian misalignment and jet lag. Bright light can be obtained by going outside (S indicates sunlight exposure) or from a light box (L), but S is always preferable to L. Intermittent bright light exposure should be sufficient during the times indicated. A light box is needed for days -1 and 0, but Henry can just seek brightly lit places for the Ls during the next few days in Beijing. The Ms on days 8–15 indicate 0.5 mg melatonin, timed to coincide with the maximum phase advance portion of the 0.5 mg melatonin PRC. This low dose should not make Henry sleepy. Ds indicate times to stay indoors and avoid bright light or, if necessary to go out, to wear very dark sunglasses. Note that Henry stays on a slightly earlier sleep schedule while in Beijing compared to when home. This makes it quicker and easier to phase advance back to San Francisco time after the return flight home. The sleep line within the rectangle on day 1 shows that it is OK to sleep on the plane and the best time for a nap (siesta time in the middle of the day) is indicated. It is good to nap whenever the sleep episodes are gradually delaying. The sleep line within the return flight rectangle on day 9 starts with an arrow indicating it is OK to go to sleep earlier, which is true whenever a schedule has gradually advancing sleep episodes.
Figure 5
Figure 5
Diagram showing a flight from Chicago to Paris, 7 time zones east, with both time lines in daylight savings time. Other symbols as in Figures 1 and 4, with green Ms for 0.5 mg melatonin and red Ms for 3.0 mg melatonin. This schedule shows what might happen to a traveler, Susan, who usually sleeps from 12:30 am to 8:00 am, and does not do any preparation to avoid jet lag until after landing in Paris. On arrival however she is careful to get the ideal light exposure pattern to help phase advance her circadian clock to Paris time according to the light PRC. However, regardless of how much sleep she obtains at night, she will be sleepy during the day, especially in the hours around her Tmin (the triangles). Susan takes melatonin before bedtime on days 1–3, a large dose of 3.0 mg, to make her slightly sleepy and help her fall asleep so early (relative to home time). It will also help phase advance her clock according to the 3.0 mg melatonin PRC. On day 4 she switches to the smaller dose of melatonin, 0.5 mg, because her circadian clock has phase advanced so far that the 3.0 mg dose would no longer coincide with the times for maximum phase advances in the 3.0 mg PRC. She takes the 0.5 mg dose at the ideal times for maximum phase advances according to the 0.5 mg melatonin PRC. Susan’s circadian clock phase advances by 1 h/day. Her Tmin reaches the sleep episode by day 4, and then her circadian misalignment and jet lag symptoms should start to subside. We do not think that this schedule is the best solution, because circadian misalignment is pronounced during the first few days after landing.
Figure 6
Figure 6
Same flight schedule as in Figure 5, but in this case Susan uses melatonin and light exposure to phase advance her circadian clock towards the destination time zone before the flight and avoids circadian misalignment and jet lag. She advances her sleep schedule by 1 h/day. She exposes herself to bright light in the morning either by going outside (S), which is best, or by using a light box (L) when it is before sunrise or otherwise impractical. She takes 0.5 mg melatonin in the afternoon timed to produce the maximum phase advance according to the 0.5 mg melatonin PRC. This low dose should not make her sleepy. The arrow within the flight indicates that this is a good time to sleep and that going to sleep earlier is encouraged, as it is whenever the sleep schedule is gradually advanced.
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References

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