Outliers: Running the numbers on jet lag

Recovering from jet lag is just a numbers game. That's the word from researchers at the University of Michigan who've calculated the optimal way to help passengers adjust as they journey across time zones. Naturally, they've also created a related smartphone app to aid weary travelers.

Using an intricate set of equations—including individuals' normal circadian rhythms and body temperatures, the distance traveled and the time changes from point A to point B—researchers were able to ascertain how much daylight individuals should expose themselves to before, during and after their trip, what time they should wake up and go to bed, and how many days it will likely take them to fully adjust to a new time zone.

“Light is the biggest driver to your circadian clock. When you travel to a new time zone, light is what's steering your body's clock to adjust to the new schedule,” said Olivia Walch, a U-M graduate student who worked on the project.

The new study, which details the “ideal adjustment schedules” for more than 1,000 possible travel scenarios—as, for example, an overnight trip between Detroit to London, or a morning flight from London to Tokyo—was published this month in the journal PLOS Computational Biology.

U-M mathematicians, along with a former student now working on his doctorate at Yale, also launched a free related iPhone app that helps realign an individual's circadian rhythms with the time of day, a tool especially useful for long-distance frequent flyers and late-night shift workers. The app is called Entrain—the scientific term for the synchronization of a person's circadian rhythm with local time.

“This is almost like a body hack, to get yourself entrained faster,” Walch said.