How To Travel the World Without Jet lag
▻http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2829880
Now that we know when to apply bright light or give melatonin pills to get the largest phase shifts, how can we help Henry minimize or avoid jet lag? Figure 4 shows one possibility. Henry uses a bright light box in the 2 h before sleep the 2 nights before the flight to China. Note that commercially available light boxes are usually advertised for the treatment of winter depression or seasonal affective disorder (SAD), but these boxes are also useful for helping to phase shift the circadian clock, and therefore for minimizing or avoiding jet lag. In addition to using the light box, Henry also goes to bed 2.5 h later on day -1 which helps place the bright light exposure closer to the Tmin and into a higher amplitude part of the phase delay portion of the light PRC (see Fig. 2). He delays bedtime by 2 h for the next 2 nights to keep up with the phase delaying circadian clock and its PRC, which is also phase delaying, so that the bright light will continue to coincide with the delay portion of the light PRC. The bright light on day -1 helps push the Tmin 2 h later, from 4:00 to 6:00 am, and the bright light on day 0 helps phase delay the Tmin another 2 h to 8:00 am. Bright light is avoided after waking (indicated by the Ds) because it could coincide with the phase advance portion of the light PRC. Thus during this time Henry would do well to wear very dark sunglasses if he needed to go outside. For the same reason, it is necessary to sleep in a dark bedroom, or if that is not possible to use an eye mask while in bed. An early study in which the sleep schedule was delayed 2 h/day and bright light from light boxes (about 2000–4000 lux) was used in the 2 h before bed showed that the Tmin of most subjects entrained to the 26 h day, i.e., they phase delayed by 2 h/day [57], so a phase delay of 2 h/day is a reasonable estimate when a light box is used. After landing, the light exposure that Henry receives (days 1–3) is unpredictable and dependent on his activities, the weather and temperature in Beijing. So we show his Tmin phase delaying by only 1 h/day. A study of subjects kept in room light (70 lux) showed that the circadian clock phase delayed by about 1 h/day with a sleep schedule delay of 2 h/day [58], so we think that 1 h/day is a reasonable estimate for how Henry’s circadian clock will phase delay after landing. If Henry happens to be exposed to enough bright light before bed, his circadian clock might phase delay even faster. The phase delays stop when complete re-entrainment is reached.