The Hidden Impact Of Jet Lag On Your Body

Waking up at odd hours is the least of your worries.
Chronic jet lag may increase risk of cancer -- and speed up cognitive decline.
Eric Marsalla via Getty Images
Chronic jet lag may increase risk of cancer -- and speed up cognitive decline.

Waking up in the middle of the night, falling asleep in your dinner and general doziness are all classic signs of jet lag. But common hallmark symptoms aren't the only way crossing time zones affects your body.

“When you jet to a new time zone, your internal circadian body clock is still on home time. And like a stubborn turtle, only slowly resets to the new time,” sleep expert Charmane Eastman, a professor in the behavioral sciences department at Rush University Medical Center in Chicago, told The Huffington Post.

A growing field of research suggests that all of this body clock resetting can wreak havoc on your insides over time. To gain insight into the effects of jet lag, researchers have turned to airline professionals like pilots and flight attendants to learn more. Here are a couple of insights about how frequent, chronic jet lag might be affecting your health.

It Might Increase Cancer Risk

Rudyanto Wijaya

Population-based studies in flight attendants and flight crews have found those individuals have higher rates of breast cancer, melanoma and prostate cancer than the general populations of adults. One differentiator, researchers suspect, has to do with their chronic jet lag -- an occupational hazard for the group.

The researchers behind those studies all note that other factors like exposure to cosmic radiation may contribute to increased cancer incidence. But another recent study conducted in mice has shown similar findings -- that mice who experienced chronic jet lag were more likely to develop breast cancer than mice on regular (non-jet-lagged) sleep-wake schedules.

It Can Hurt Your Memory

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Research has also suggested chronic jet lag might actually speed up cognitive decline. Increased levels of the hormone cortisol have been shown to negatively affect cognitive functioning, and one study in flight crews found that individuals who worked international long-distance flights had higher cortisol levels on average compared with ground crews.

Within this group of international flight crew members, those who had been on the job longer tended to score lower on memory tests compared with members of the ground crew and the members of the flight crew with fewer years of experience.

The researchers of that study note the findings suggest that chronic international flying could increase how much cortisol the body produces -- and that the higher cortisol levels may actually be the cause of the poorer memory test results.

The sooner you re-sync the better

The good news when it comes to all the internal body clock shifting associated with jet lag is that getting your body back on track (and on time) after traveling is one of the best strategies to protect yourself against the long-term consequences of being on a shifted schedule, Eastman said.

Circadian misalignment -- sleeping, working, eating, and being awake at the wrong times according to your body's internal clock -- is the real problem, she explained.

It's known from other studies in night shift workers, who also have misaligned internal body clocks, that those individuals are also at increased risk for cardiovascular disease, diabetes, ulcers, obesity, and certain cancers, too -- which tells us that reducing misalignment as much as possible is probably best for your health, she said.

What to do if you have a trip coming up

Headed abroad next week?

First of all, it's important to note that the negative associations above have been found in airline pilots and crews who are jet lagged very frequently -- similar studies do not exist in travelers who take a vacation or two a year. And the study in mice mimicked flying from Amsterdam to Australia once a week and back the following week for an entire lifetime. Eastman added that she didn't know of any data to show exactly how much jet lag is enough to affect your long-term health.

But even if your cross-continental travels aren't upping your long-term chronic health risks, it still feels a whole lot better to feel well-rested when you reach your final destination, whether you're traveling for business or pleasure.

As a general rule, it takes about a day to adjust for each time zone you cross, with the adjustment being quicker when traveling west, Eastman said. To better keep your body clock on schedule, the best strategy is gradually shifting your clock BEFORE you travel by shifting both your sleep and light schedules, she added.

Here's what she suggests: For traveling six time zones (like New York City to Paris), try shifting your sleep an hour earlier each day for three days ahead of your trip. And on those days, avoid bright lights in the two to three hours before sleeping and take 3mg or less of melatonin about five to seven hours before heading to bed. Then be sure to get outside in some bright sunlight when you do wake up. If there's no natural sunlight one morning, use a light box intermittently for about two to three hours.

Don't drive after taking melatonin, Eastman warns. And other experts have agreed while it is safe to use to help avoid jet lag, melatonin should not be used regularly to treat insomnia or other sleep disorders.

You can also try coping with jet lag by starting out well-rested, exposing yourself to sun light when you arrive at your destination, and drinking plenty of water.

Sarah DiGiulio is The Huffington Post’s sleep reporter. You can contact her at

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