Jet Lag
Medical Author: John P. Cunha, DO
Medical Editor: Melissa Conrad Stöppler, MD
What is jet lag?
Jet lag, also called desynchronosis, is a temporary disorder that causes fatigue, insomnia, and
other symptoms as a result of air travel across time zones.
What are other symptoms of jet lag?
Besides fatigue and insomnia, a jet lag sufferer may experience
anxiety, constipation, diarrhea, confusion, dehydration, headache,
irritability, nausea, sweating, coordination problems, and even memory loss. Some
individuals report additional symptoms, such as heartbeat
irregularities and increased susceptibility to illness.
What is a time zone?
A time zone is a geographical region which has the same time everywhere within
it. The world has 24 time zones, one for each hour in the day. Each zone runs
from north to south in strips that are approximately 1,000 miles (1,600 kilometers) wide. (The actual width of each zone varies to accommodate political and geographical boundaries.) As the earth rotates, dawn occurs at a set hour in one time zone, then an hour later in the time zone immediately to the west and so on through the 24-hour cycle. Thus, in the U.S., when it is 6 a.m. in the Eastern Time Zone, it is 5 a.m. in the Central Zone, 4 a.m. in the Mountain Zone, and 3 a.m. in the Pacific Zone.
Why does jet lag occur?
The cause of jet lag is the inability of the body of a traveler to immediately adjust to the time in a different zone. Thus, when a New Yorker arrives in Paris at midnight Paris time, his or her body continues to operate on New York time. As the body struggles to cope with the new schedule, temporary insomnia, fatigue, irritability, and an impaired ability to concentrate may set in. The changed bathroom schedule may cause constipation or diarrhea, and the brain may become confused and disoriented as it attempts to juggle schedules.
How does the body keep time?
A tiny part of the brain called the hypothalamus acts like an alarm
clock to activate various body functions such as hunger, thirst, and
sleep.
It also regulates body temperature, blood pressure, and the level of
hormones and glucose in the bloodstream. To help the body tell the
time of day, fibers in the optic nerve of the eye transmit
perceptions of
light and darkness to a timekeeping center within the hypothalamus.
Thus,
when the eye of an air traveler perceives dawn or dusk many hours
earlier
or later than usual, the hypothalamus may trigger activities that the
rest
of the body is not ready for, and jet lag occurs.
Next: What is the role of melatonin in jet lag ? »
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