You may have seen the recent Saturday Night Live skit about ‘Muammar al-Gaddafi' attributing his rambling UN speech to jet lag. While the skit was funny, jet lag is not.
Consider the possible impact of jet lag on real life political leaders as they travel half way around the world to engage in sensitive negotiations. They need to be at the top of their game, not groggy with brain fog. What about the effects that jet lag may have on the complex business schemes that are transacted daily by fatigued, time pressured and jet lagged executives? "Deal or no deal" can be a difficult decision in the best of times - let alone when red-eyed and raw with jet-lag. And what about those of us with simpler goals? We want to enjoy our fun in the sun, but many vacationers may find it difficult to enjoy a significant part of their vacation because they have a slow recovery from their lengthy flight.
Jet lag is a type of circadian rhythm disorder that is new to the modern world. Circadian rhythms evolved to allow organisms to benefit from preparing for predictable changes in the environment before they occur. As an example, for a creature that has to find food during the day, having a mechanism to wake up as the sun is rising, even on cloudy days, is very beneficial. The circadian or 24 hour system can slowly adapt to changes in the environment, say for example, as the period of daylight shortens in northern latitudes in the fall and winter. Jet lag is a disorder unknown before the 20th century as no one before the invention of the airplane could travel fast enough to cross enough time zones to affect the circadian system. With older forms of transportation, the circadian system has a chance to slowly shift to keep up with changes in the difference between the internal and external clocks - as when sailing ships slowly made their way around the world. Jet lag affects east-west travel rather than north-south travel as there is no change in time zone with north-south travel. Being very far north or south can, of course, lead to other circadian problems, such as those experienced by Antarctic scientists who spend months in the dark.
Jet lag occurs when there is a temporary mismatch between the internal timing of the sleep wake cycle and the external time demands for the sleep wake schedule of the changed time zone. Symptoms are usually experienced if three or more time zones are crossed and appear within a day or two of being in the new time zone. Generally, the more time zones crossed the worse the symptoms and the longer they persist. With travel of seven time zones or more the internal clock may shift opposite of the direction of travel. This results in severe and prolonged jet lag. A significant problem is exposure to light at inappropriate times as this can shift the internal clock in the wrong direction. Symptoms typically include disturbed sleep, impaired functioning and decreased alertness. Traveling eastward is usually more difficult to adjust for than westward travel. This is the case, at least in part, because you can generally force yourself to stay up later but cannot make yourself fall asleep.
To see how this works, imagine a transcontinental round trip from New York to Los Angeles. On the first night of the trip there is a three hour time change so that when the clock in Los Angeles says is it 11 pm, your usual bed time, your internal clock, set to New York time, feels that it is 2 am. This is disruptive to sleep but generally less so than the reverse trip. After several days in Los Angeles the internal clock shifts to match the external demands of the west coast time zone. In west to east coast travel, the clock in New York says it is 11 pm, your usual bed time, while your internal clock feels that it is 8 pm - an hour when it is usually very difficult to go to sleep. Generally, it takes about one day in the new time zone to acclimate to each time zone shift. Symptoms of jet lag are further complicated by the often stressful conditions of long distance travel - long flights spent in an uncomfortable sitting position, unfamiliar environments, poor quality food, excessive use of caffeine and alcohol and so on.
For most people, jet lag can be endured and will gradually correct itself with enough time in the new time zone. For people working in the airline industry, serving in the military or who have business or government work that requires frequent travel, jet lag may be a greater concern. For example, some female airline personnel have been reported to experience menstrual symptoms associated with frequent travel. And we can only imagine what damage has been done to international relations and what poor business deals have been worked out by overly stressed, jet lagged people. In the next post I will discuss ways of speeding up the process of coping with jet lag. In the meantime, Bon Voyage!