You’ve just flown into Boston from London, and you’re staying with friends. It’s time for happy hour and dinner. They’re talkative and lively, ready to party. But you, you’re a basket case. You haven’t slept much in the last 24 hours, nor eaten on a familiar schedule, and your body thinks it’s past midnight.

Hours later, they finally let you go to bed. You’re exhausted, but you can’t sleep well. When you finally arise the next morning, things are not much better. It’s possible you may feel anxiety, have some bowel disorder and be dehydrated, as well as have a headache and be irritable.

Nausea, sweating, coordination problems, dizziness and even some memory loss are possible symptoms of your condition. In some cases, there may be heartbeat irregularities, as well.

If you are otherwise healthy, then it’s most likely that you’re suffering from desynchronosis or, more commonly, jet lag. The severity of these symptoms vary from person to person, but are inevitably at least disorienting.

What is jet lag?

Jet lag means that you’ve traveled very fast, jet speed, from east to west, or vice versa, and crossed at least one time zone. One or two time zones is not usually very noticeable, but three or more usually has disturbing effects. Some feel that traveling west to east is more difficult than east to west.

Interestingly, traveling north to south or south to north at the same speed for the same distance does not incur jet lag. And traveling by bus or train is so slow that jet lag is seldom a problem.

What has happened is that your normal daily rhythms are out of sync, and your inner body clock has become disoriented. It’s not sure whether you should be awake or asleep or eating and, if so, what meal. And why is the sun up at this hour?

Jet lag is a temporary condition that goes away at different speeds for different people, but a common guideline is that it takes about a day for each time zone you cross. So you can imagine the constant psychological and emotional upheaval there must be for people who regularly travel cross country for a couple of days at a time.

In addition to rapid travel across time zones, a condition similar to jet lag is sometimes experienced by those who work a swing shift schedule: 9 a.m. to 5 p.m. some days, 4 p.m. to midnight on others, for example. There are also some sleep disorders that can produce effects like jet lag.

What is this clock, and where?

Your body actually has several different rhythms, cycles that may occur daily, weekly, monthly and more. The one that is most disrupted by jet-speed, east-west travel across time zones is the one that happens approximately daily, circadian.

A small part of your brain called the hypothalamus has several essential functions, including producing the hormones that control different cells and organs. Its primary function is keeping your body in balance, to which end it regulates temperature, thirst, hunger, sleep, mood, sex drive, breathing, blood pressure and more.

Your body clock resides in a small V-shaped cluster of cells in the hypothalamus. It’s like a brain pacemaker that regulates your circadian rhythm of sleeping and waking. It’s like an hour hand on your watch coordinating not only the timing of wakefulness and arousal, but also the stages of sleep.

How does it get off-schedule?

Your clock is largely selfregulating, but it relies on external cues to keep it consistent with a 24-hour schedule. Technically, these cues are called “zeitgebers,” which is German for “time givers.”

The most influential zeitgeber is the light that strikes your eyes, even with people who are blind. As the daylight changes slowly with the seasons, your clock unconsciously resets itself to accommodate to the changing light pattern. However, if the change in the zeitgebers is too fast, your clock can’t adjust itself to keep up, and you wind up with jet lag.

Time, although an imaginary concept created by us humans, has an effect on your body clock. As you read your watch, for example, or keep to work, train and other schedules, you are demanding that your body be aware of the timing for different tasks and social events. This awareness puts a cognitive pressure on your body clock to stay on schedule. So when the dinner hour at your travel destination differs significantly from your accustomed schedule, then your clock naturally gets confused about what you want to do.

In addition, in that small nucleus of your brain where your body clock resides, there are receptors for a hormone called melatonin. Melatonin is produced in a regular daily rhythm by a gland deep in your brain and between the two halves of it; this is the pineal gland. Research has shown that the melatonin level climbs after dark and ebbs after dawn. It causes drowsiness for some people, and its light-sensitive nature helps regulate your circadian cycle of sleep and wakefulness. In some sense, it is the lackadaisical regulation of this and other hormones that results in the jet lag experience.

What to do about jet lag

You can do a lot to minimize the effects of jet lag.

First, stay fit. This means getting daily exercise and plenty of rest, as well as eating a balanced diet.

Next, drink plenty of water during your trip. Avoid alcohol and caffeine, which may make the jet lag symptoms worse.

Move around on the airplane. At least once an hour, get up and walk the aisle.

If you are not on a tight schedule, consider breaking up your long trip into shorter segments. Of course, this may be a bit difficult if you’re flying across the Atlantic or Pacific oceans.

If you’re staying for several days at your destination, immediately change your schedule to the local one. You can also start changing your schedule over a period of days before you leave on your trip. For myself, if I’m staying for just a day or so in California, for example, I find it better to try to stay as close as possible to my eastern time schedule.

For some people, using over-the-counter melatonin has a beneficial effect. Do this only after consultation with your doctor, as melatonin can have side effects like daytime sleepiness, headaches and dizziness. It can also interact negatively with other medications you may be taking, including blood thinners and birth control pills.





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