The jet-lag mobile app developed by University of Michigan mathematicians reveals previously unknown shortcuts that can help travellers snap their internal clocks to new time zones as efficiently as possible.
"Our predictions show the best and quickest ways to adjust across time zones," said Danny Forger, a professor at the U-M College of Literature, Science, and the Arts.
The new app, called Entrain, is believed to be the first to take a numbers-based approach to "entrainment," the scientific term for synchronising circadian rhythms with the outside hour.
Entrain is built around the premise that light, particularly from the Sun and in wavelengths that appear to our eyes as the colour blue, is the strongest signal to regulate circadian rhythms.
These fluctuations in behaviours and bodily functions, tied to the planet's 24-hour day, do more than guide us to eat and sleep. They govern processes in each one of our cells.
Short disruptions such as jet lag and its symptoms of fatigue and insomnia can affect mood and performance.
Scientists have linked regular disturbances and disorders of the system to depression, certain cancers, heart disease and diabetes.
The shortcuts the app offers are custom schedules of light and darkness depending on the itinerary.
The schedules boil down to one block of time each day when you should seek the brightest light possible and another when you should put yourself in the dark, or at least in dim light, researchers said.
If the app prescribes "bright outdoor light" in the middle of the night, a therapeutic light-box can do the job, its shortcuts sometimes require odd hours.
The study, published in the journal Public Library of Science Computational Biology, relies on two leading mathematical models, or sets of equations, that have been shown to accurately describe human circadian rhythms.
The researchers used these equations and a technique called optimal control theory to calculate ideal adjustment schedules for more than 1,000 possible trips.
People can enter their typical hours of light and darkness in current time zone, then choose the time zone they are travelling to and when, as well as the brightest light they expect to spend the most time in during the trip.
The app offers a specialised plan and predicts how long it will take to adjust.