Why Jet Lag Is Worse Traveling From West to East

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Photo: Yiu Yu Hoi/Getty Images

In the 1966 column that coined the term, Los Angeles Times reporter Horace Sutton describes jet lag as “a debility not unakin to a hangover.” A peril of the jet-set lifestyle, he reasoned that it “derives from the simple fact that jets travel so fast they leave your body rhythms behind.” In a 2004 essay, travel writer Pico Ayer captured the way it defamiliarizes you with the experience of being alive, noting that you “get up for lunch, and then remember that you have eaten lunch six times already.” You want to do your morning jog at 10 p.m. You sleep all day. When Lil Wayne raps about how codeine has him “movin’ slower than a caterpillar race,” you nod with dim recognition. It’s a dark, disorienting experience. And, weirdly enough, jet lag appears to be directional.

As a new paper written up in the New York Times finds, jet lag gets worse when you’re traveling east — like from New York to Reykjavík, as all my friends seem to be doing — than it is west, like from the innocently intracontinental flight from New York to Los Angeles. “The body’s internal clock has a natural period of slightly longer than 24 hours,” says Michelle Girvan, co-author and a physicist at the University of Maryland, “which means that it has an easier time traveling west and lengthening the day than traveling east and shortening the day.” Doubly strange, traveling through more time zones can be easier on you than fewer, at least according to Girvan’s model. Flying westward across nine time zones would lead to eight groggy days of recovery, but if you did the same distance going east, it would take 13 days.

As Joanna Klein notes at the Times, scientists think that jet lag is governed by the “suprachiasmatic nucleus,” a cute little clump of 20,000 nerves inside your hypothalamus. Those cells get light from your eyeballs, which helps tell the brain when it’s time for rest. But if you take a long-haul flight, your suprachiasmatic nucleus, despite its best efforts, can’t find the signals that it needs to operate. Most people’s bodies are more primed to handling longer days — presumably that’s why you could pull an all-nighter in college and still drink the following evening — and that’s why you have trouble with the “shorter day” jet lag.

The “solutions” to jet lag include subjecting yourself to “brief flashes of bright light delivered at specific intervals” during and after travel, following the fasting and sleep schedules dictated by the StopJetLag app, and according to one Serbian tennis star, staying up until 9 p.m. wherever it is you are, and getting onto a regular, local meal schedule (eat breakfast at breakfast). That’s the sadly fitting truth about chronological discombobulation: The only cure is time.