What is jet lag?
The earth is divided into multiple time zones (Eastern, Pacific, European, Asian) based on the timing of sunrise and sunset when you travel around the planet. For example, when you travel westward, sunrise and sunset are delayed as compared to your point of origin. When you awaken at your usual time, it will be earlier in the daytime and by the same token when you feel sleepy, it will be earlier at night. It is generally easier for people to adjust to westward travel as it is easier to get up on time.
By contrast, traveling eastward leads to an advance of sunrise and sunset as compared to your point of origin. This means that the clock time will be ahead of your normal body’s wakeup time. It will be very difficult to wake up earlier than usual.
Both changes lead to a desynchrony between when your body desires wake and sleep, and the light-dark cycle (sunrise or sunset). This can lead not only to impairment in attention and fatigue, but can also cause changes in mood, stomach upset and fatigue.
In addition to time differences, differences in altitude at your destination can also lead to sleep problems. Higher altitudes can cause “altitude sickness” which includes shortness of breath, stomach upset, headaches and insomnia. This is usually caused by a rapid ascent to a higher altitude without giving the body enough time to acclimate to the lower oxygen level and increased barometric pressure. When this is severe, this can cause life-threatening congestion in the lungs which requires immediate descent to a lower altitude.
What can I do to feel better while traveling?
If you are traveling, it is a good idea to be well-rested (and not sleep deprived) prior to travel. The rule of thumb is that it takes about one day to adjust your sleep-wake schedule for each 1-to 2- hour time zone change. If your travel schedule permits, you can maintain your usual wake time and bedtime and control the light in your environment to stay on your original schedule. If you want or need to adjust to the new time zone, you can start advancing or delaying your wake time either prior to travel or upon arrival to correspond to your new anticipated schedule. You would do the reverse preparation for returning to your original time zone.
Changing your wake time may be difficult, and you may want to use assistance to make this adjustment. Different combinations of treatments have been successfully used to assist this process. Light therapy has been used, and the timing of light exposure can promote either an earlier awakening or a later bedtime. Sleeping aids (including sedative hypnotic medications or melatonin-type medications) can also be used to facilitate sleep onset. Finally, strategic napping and stimulants can be used to maintain daytime alertness. For people who routinely travel and experience frequent time changes and jet lag, consultation with a sleep medicine physician is recommended to assist in the best combination of the above medications.
Altitude sickness is also preventable. Acclimatization, or a slow ascent to altitude, can prevent altitude sickness. If this cannot be accomplished, then there are several medications that can help speed up the body’s adjustment to a higher elevation, including acetazolamide and dexamethasone (or prednisone).
If you are traveling in the westward direction, you may benefit from having increased light exposure in the early evening hours at your destination. This will delay your bedtime and wake time to better fit the local schedule, especially if most of your planned events are in the late evening. If you have early morning and afternoon events planned, you will be feeling great. Coming home will be more difficult (see eastward travel).
On the other side, if you are traveling eastward, you will have the most difficult time adjusting when you arrive and will feel much better returning home. You will benefit from increased light exposure in the morning at your destination to try to help you awaken, and a quiet dark room at night to help you fall asleep. If you are planning to fly east and need to be able to attend morning events, you may want to start adjusting your sleep prior to departure. The rule of thumb, take the hour of your bedtime, subtract the number of time zones you cross, and calculate what your new bedtime will need to be. For example, if your bedtime is 10 pm (2200 hrs.) and you cross seven time zones, your bedtime in the new time zone will be 3 pm (1500 hrs.) when you arrive. In simple terms, the more time zones you cross, the earlier and earlier you want to make your bedtime before you leave. If more than 2-3 time zones are being crossed, the more likely you will benefit from one week of advancing your bedtime, increasing morning light, and possibly add a melatonin-type medication. You may also require a stimulant in the morning if a high vigilance activity is required (i.e., long drive) and you are feeling sleepy.
As you can see, the saying about travel “West is best, east the least,” describes fairly well how easily people can delay their bedtime and how poorly we are able to go to bed earlier. As described in earlier chapters, the pressure to fall asleep is a combination of light or dark exposure and activity (sleep debt or tiredness). It is hard to tell our body to go to sleep when we do not feel tired.