It's the caged-mouse syndrome of air travel -- you feel crammed into your seat on a long-distance flight with little to munch on except a bag of pretzels.
But you better hope you beat jet lag better than a mouse.
A study at the University of Virginia released during the height of Thanksgiving and Christmas travel seasons showed that a majority of elderly mice died while being subjected to the equivalent of a Washington-to-Paris flight once a week for eight weeks. More intense forms of jet lag sped up the death rate in the elderly rodents, the study found.
For decades, flyers have stoically battled the modern-age problem of jet lag, viewing its accompanying grogginess, burning eyes, headaches, insomnia and fatigue as more of a nuisance than a potential health issue.
The study has focused new attention on the problem and raised questions about whether severe jet lag can be harmful to health. It also has drawn attention to work by other researchers looking into ways to help vacationing families and business travelers avoid jet lag. The study is one of the first hard scientific looks into the health effects of jet lag, experts said.
The condition has become such a common scourge of the jet age that an entire industry has emerged on the Internet, offering such solutions as acupressure kits, homeopathic pills and light-enhancing visors. Many travelers have invented their own treatments: slurping down gallons of coffee, dunking heads in ice-cold water, taking naps, jogging and popping sleeping pills and homeopathic remedies. But researchers say few of those remedies are backed by science.
In the study, younger mice seemed to rebound more quickly and were not immediately harmed by the jet lag. Simulated jet lag conditions were created by advancing and delaying the rodent's exposure to light.
Researchers aren't sure what conclusions to draw from the results.
Gene Block, the report's co-author, said older mice might be more susceptible to sudden light changes than younger mice. Or, he said, jet lag might be a health problem that builds up in younger subjects, causing future maladies.
To further explore the issue, his researchers have launched another set of tests to determine whether jet lag causes long-term health consequences in younger and middle-age rodents, Block said minutes before boarding a 14-hour flight to Japan from Washington.
"I feel like a subject in the experiment," said the 58-year-old, who recently returned from a conference in Italy. "Like many people, I am finding it more difficult to cope with jet lag as I get older. . . . I would like to know whether it's a phenomenon of old age or whether it is something I really have to worry about."
Block's study also hinted at what flyers have been saying for years: It is more difficult to adjust to time zone changes when flying east. The researchers found that 53 percent of elderly mice died when they were subjected to a simulated weekly flight from Washington to Paris over the eight-week study. The death rate dropped to 32 percent of elderly mice on a simulated Paris-to-Washington route, according to the study, which was published last month in the journal Current Biology. Seventeen percent of the mice in a control group died in the eight-week study.
Research has identified links between night-shift work and chronic health problems. And doctors and aviation experts have worked hard to help pilots and flight attendants mitigate the effects of jet lag to ensure they can function properly in the air.
Jet lag is caused when people fly across time zones. Many factors, including daylight, sleep cycles, hormones and other natural rhythms, play a role in how humans' complicated internal clocks handle it.
Researchers say the only way to truly avoid jet lag is for travelers to gradually prepare before leaving on their trips.
Charmane I. Eastman, a professor and director of the Biological Rhythms Research Lab at Rush University Medical Center in Chicago, believes that flyers can more easily cope with jet lag by adjusting their sleep schedules before traveling.
If headed east from the Washington area, for example, travelers should go to bed an hour earlier each night and wake up an hour earlier each morning for several days before leaving town.
When travelers wake up, they should get sunlight or use a "light box" to help trigger changes in their biological clocks. Travelers should also consider taking small amounts of melatonin, a hormone, five hours before going to sleep to help them adjust to their future time zone, Eastman said.
The only other way to avoid jet lag on overseas trips: "Take a boat," she said.
There are also ways to mitigate jet lag once you land. If heading to Europe from Washington, most people should wear dark sunglasses after landing until about 11 a.m. Exposure to too much light too early can delay adjustment to new time zones, Eastman said.
After 11 a.m., travelers should try to get as much sunlight as possible to help kick-start the body's clock, she said.
Several veteran travelers said they would have a difficult time switching schedules under Eastman's plan and said booking a cruise was an inefficient option.
They have found their own ways to cope.
Steve Solomon, 30, a consultant who lives in Gaithersburg, sets his watch to his destination's time zone before he takes off "to get your mind into the right mind-set." He also avoids alcohol and drinks a lot of water.
"I view it as more of a hassle than anything else," he said. "You have to run with the punches."
Carol Lane, a 42-year-old free-lance advertising and marketing writer, says she relies on homeopathic pills she buys at a health food store.
Even with the pills, though, she said she hadn't been able to adjust to jet lag as well as she did a few years ago.
"When you are in a particularly bad bout, you are just so walloped," she said. "I'm an old mouse, I guess."