Why jetlag is worse flying east

As someone who has family in Sri Lanka and New Zealand, this necessitates periodic long flights. Fortunately for me, I do not suffer as much from jet lag as some others do. I am usually back to normal within a day of arrival at my destination whereas I have friends who take up to a week. My personal hypothesis is that the after-effects of jet lag are caused largely by tiredness due to lack of sleep. As a result, on these long flights, I ignore all the in-flight entertainment and instead spend as much of my time as possible sleeping, only waking up to eat or read. Fortunately I can sleep seated.

Nathaniel Scharping reviews a new study that looks at jet lag more closely.

When you step off a plane in another country, the first thing you usually want to do is hit the hay. It’s the sleepy side effect of travel known as jet lag.

Experienced travelers power through fatigue and wait until nighttime to get some shut-eye in an attempt to match the natural cycles of their new locale. While some people acclimate to time-zone jumping better than others, most agree that traveling eastward is a more daunting challenge to our sleep cycle, but it’s not clear why that is.

Because I sleep so much on the plane, I do not have strong feelings of fatigue on arrival nor do I find it hard to stay awake until the normal bedtime in the new time zone.

Now, researchers from the University of Maryland have posited a mathematical explanation for the west-to-east conundrum. Previous research has found that most people’s circadian cycle is slightly longer than the length of an actual day — around 24.5 hours, and other studies have shown that when forced to make an adjustment, our minds sometimes align our internal clock in the wrong direction — think moving the hands of the clock counterclockwise to move forward three hours.

The researchers found that traveling eastward across nine time zones was the most jarring to the circadian cycle. That’s because nine hours lies at the borderline between when our minds decide to set our clocks forward or backward, necessitating the largest readjustment. Nine hours east will cause our minds to shift the clock fifteen hours backward, while any more will flip the direction of the reset, shortening it.

The fact that our circadian rhythm is slightly longer than an Earth day exacerbates the problem, increasing the time it takes to adjust to a new time zone. Traveling three time zones east, for example, requires just over four days of readjustment, while three time zones west takes a bit less than four, researchers say. A trip spanning six time zones east or west could mean nine and six days of recalibration, respectively.

I too had noticed that jet lag is less pronounced going west than going east and I put that down to the fact that when you are going west, the daily cycle is longer and so you have longer periods of night and darkness, making sleep easier. Since Sri Lanka is about nine hours east of Cleveland and thus should produce the worst effects of jet lag, why is it that I take so much less than the usual time to recalibrate?

Some people find recovering after a long flight to be no more than an annoyance, while for others, it can be a heavy burden. The reasons for this can be explained by differences the systems that regulate and maintain our mental clocks, the researchers say. Some people respond more strongly to sunlight than others, and some people display better connectivity between the neurons that operate our circadian cycle.

The prescription for mitigating jet lag is the same for everyone though. Get as much sunlight as possible to saturate your mind with the correct temporal signals, wait to sleep until it gets dark, and try to pre-set your circadian rhythm by using artificial light to mimic the time zone you’re headed to.

That remedy sounds complicated. I will continue my own policy of simply sleeping as much as possible. I have recommended it to others and they say it has helped. The problem is that some people find it almost impossible to sleep seated on airplanes. As a result they get bored and watch a lot of films and this may cause a double-whammy, lack of sleep and over-stimulation of the mind.


  1. Reginald Selkirk says

    If you’re flying a couple hours, it might make a difference. But if you’re flying half way around the globe, I don’t see why it would matter if you went east or west.

  2. Kreator says

    I’m one of the lucky few: the time it takes for me to recover from jetlag is zero seconds, as I don’t experience it at all. And that despite being of those people who don’t get much sleep on a plane and watch films!

  3. chigau (ever-elliptical) says

    My trips are usually to an 8 hour difference location.
    I try to get extra sleep for a couple of days before the flight and once on the plane, I put myself on destination time.

  4. Mano Singham says


    It matters because it is not just the final time difference that matters. People tend to sleep and wake up with the ambient natural light. When traveling West, the ‘nights’ are longer. Of course, the days are longer too but a lot of my international flights tend to leave at night, so I have dinner on the plane and then go to sleep.

  5. Pierce R. Butler says

    What tricks do politicians, diplomats, & others required to zoom around, look chipper and perky immediately upon arrival, and sometimes even carry out complex negotiations with minimal delay, rely on?

  6. Mano Singham says


    According to my sleep theory, they fare better because they travel first or business class and have very comfortable seats that actually recline fully and thus they can sleep better.

  7. Crimson Clupeidae says

    I find 1-3 hours pretty hard to adjust to, regardless of which direction I’m flying. The odd thing is that when I travel to Europe (6-8 time difference), I usually adjust within a day.

  8. Pierce R. Butler says

    Mano Singham @ # 6: According to my sleep theory…

    Which seemingly works for you because you have a catlike ability to snooze at will.

    I can’t help but suspect Bill Gates & Barack Obama rely on much fancier and pricier techniques.

  9. Trickster Goddess says

    I’m a night person and when I travel east to visit my parents who are early morning people and expect me to be on their schedule, what should be a three-zone difference is actually more like a 6 or 7 time zone difference! Even if I were to stay there long term, it isn’t something my circadian rhythm will fully adapt to — I just don’t tick that way.

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