VOA慢速英语2015 时差是如何产生及如何避免时差（在线收听）

What Causes Jet Lag and How to Avoid It 时差是如何产生及如何避免时差

From VOA Learning English, this is the Health & Lifestyle Report.

Our bodies react to daylight. In fact, light is the most powerful environmental signal for re-setting our biological clock. Part of the job of the biological clock is to control when we sleep and when we wake.

Light has a similar effect on a common insect: the fruit fly. So says Logan Roberts, a PhD student at the University of California, Irvine. He was the lead writer of a report on the subject.

A long flight can affect one’s biological block, sometimes for days. Air travelers can get very tired and develop unpleasant feelings when they fly great distances across time zones. The natural order of things can become unbalanced on long, overseas trips from east to west or from west to east.

In experiments, Logan Roberts and other researchers removed the brains of genetically-engineered flies. The insects’ genes were changed for the purpose of this study. The researchers kept the brains alive in a laboratory. They used bursts of light to change their circadian rhythm by two hours.

A circadian rhythm is a 24-hour cycle, a series of events or actions that happen in the same order, over and over again.

This natural system tells our bodies when to sleep and helps to control many other processes. This internal body clock is affected by environmental signals, like sunlight and temperature.

The researchers studied how the brains of the fruit flies reacted. Mr. Roberts says that by using a low-light-sensitive camera, they could see activity in individual neurons.

"The activity is measured by the amount of light these single neurons emit. They have a firefly gene engineered into these flies, so that when these cells are active, they actually, literally light up in the brain and we can measure that activity."

The new report was published in the journal Current Biology. The study is the first to document in real-time how neurons react to changes in lighting like those affecting the jet-lagged traveler.

Logan Roberts uses the word desynchronized when talking about the study and jet lag. This means to cause a process that takes place at times or in cycles independent of another process. In unscientific terms, you might say “out of sync” or “out of whack.”

"And we can see that some of these cells change their activity when a light is shown directly on them. They actually become desynchronized amongst the groups and within the groups. So that sense of de-synchronization - or … when you feel out of whack with the environment after you experience jet lag - your nervous system actually reflects that same thing in becoming de-synchronized within itself."

In this state of de-synchronization, he adds, communication between some neurons weakens. He says using light to temporarily reset your biological clock before you travel could help to reduce symptoms when you arrive at your final stop.

"We believe that if we can harness that and actually use that to actually induce this de-synchronization, this weakening of communications between these cells before jet lag, before, say, you would travel rapidly across time zones, we believe that could actually accelerate recovery from jet lag."

Mr. Roberts says the model used to study jet lag in fruit flies can be used in the study of other human conditions. He says that when our body clock is out of sync, we can be at greater risk for diabetes, cancer and diseases of the nervous system.

Tips to avoid jet lag

Light therapy is not the only treatment for jet lag. There are other things you can do to feel less tired the next time you travel. Sleep experts at the medical website WebMD have these suggestions on how to fight jet lag.

1. Try changing your meal and sleep times before you go

Several days before you travel, start moving your bedtime and hours for meals closer to the times you plan to eat and sleep on your trip.

2. Start making small changes while in flight

Change your watch when you get on the airplane. This is playing a trick on the mind. But it can help you to start thinking of the time at the other end of the flight.

Try to sleep on the plane if it is nighttime in the place where you are going. Try to stay awake if it is daytime.

3. Arrive early

If you are traveling for work or for a personal reason, try to arrive a few days early, if possible. This will give your mind and body more time to correct to the new hours. 

4. Drink water

Drink lots of water before, during, and after your flight. Avoid drinking alcohol or caffeine a few hours before you plan to sleep. Alcohol and caffeine can interfere with sleep.

5. Move around

During your flight, get up and walk around or stretch every so often. But after you land, avoid heavy exercise near bedtime. Exercise near bedtime can delay sleep, whether on an overseas trip or at home.

And that’s the Health & Lifestyle Report, I’m Anna Matteo.

If you travel, what are some tips you use to make it more enjoyable?

Words in This Story

desynchronize – v. to cause a process to occur at times or in cycles independent of another process

neuron – n. a specialized cell transmitting nerve impulses; a nerve cell

circadian rhythm – n. a 24-hour cycle that tells our bodies when to sleep and regulates many other physiological processes