- Causes of Fatigue Slideshow Pictures
- Take the Sleep Quiz
- Foods That Help or Harm Your Sleep Slideshow Pictures
- Patient Comments: Jet Lag - Remedies
- Patient Comments: Jet Lag - Symptoms
- Patient Comments: Jet Lag - Coping
- Patient Comments: Jet Lag - Direction of Travel
- What is jet lag?
- What are other symptoms and signs of jet lag?
- What is a time zone?
- What causes jet lag?
- How does the body keep time?
- What is the role of melatonin in jet lag?
- Does the direction of travel matter?
- Do the symptoms of jet lag vary in intensity?
- What are risk factors for jet lag?
- How long does jet lag last?
- Should people take melatonin for jet lag?
- Are there any remedies for jet lag? Is it possible to prevent jet lag?
How does the body keep time?
Our bodies have a sort of internal biological clock that follows a 24-hour cycle, called a circadian rhythm. 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. So, 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.
What is the role of melatonin in jet lag?
Melatonin is a hormone that plays a key role in body rhythms and jet lag. After the sun sets, the eyes perceive darkness and alert the hypothalamus to begin releasing melatonin, which promotes sleep. Conversely, when the eyes perceive sunlight, they tell the hypothalamus to withhold melatonin production. However, the hypothalamus cannot readjust its schedule instantly; it takes several days.
Does the direction of travel matter?
Yes. Travelers flying north or south in the same time zone typically experience the fewest problems because the time of day always remains the same as in the place where the flight originated. These travelers may experience discomfort, but this usually results from confinement in an airplane for a long time or from differences in climate, culture, and diet at the destination location. Time differences do not play a role.
Travelers flying east, on the other hand, typically experience the most problems because they "lose" time. For example, on an international flight from Washington, D.C., to Mecca, Saudi Arabia, a traveler loses eight hours. Meals, sleep, bowel habits, and other daily routines are all pushed ahead eight hours.
Travelers flying west "gain" time and usually have an easier time adjusting than eastward travelers. However, they too experience symptoms of jet lag after landing because they still must adjust to a different schedule.
Do the symptoms of jet lag vary in intensity?
Yes. People flying across only one or two time zones may be able to adjust without noticeable effects of the time change. Those flying across three or more time zones will likely develop noticeable symptoms of jet lag. Generally, the intensity of symptoms varies in relation to the number of time zones crossed and the direction of travel. People also vary in their susceptibility to jet lag symptoms and the severity of the symptoms.