University of Michigan (UM) mathematicians say the app uses previously unknown shortcuts to restore a person’s internal clock as efficiency as possible.
“Overcoming jet lag is fundamentally a math problem, and we’ve calculated the optimal way of doing it,” said Danny Forger, Ph.D., math professor at UM.
“We’re certainly not the first people to offer advice about this, but our predictions show the best and quickest ways to adjust across time zones.”
Traditional guidelines recommend allocating one day of recovery for each time zone crossed.
The new iPhone app, called Entrain, is believed to be the first to take a numbers-based approach to “entrainment,” the scientific term for synchronizing 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 color blue, is the strongest signal to regulate circadian rhythms.
These fluctuations in behaviors 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.
Pilots, flight attendants, and shift workers, which make up more than 10 percent of the American workforce, are particularly susceptible.
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. You don’t even have to be asleep.
“If you must go outside, you can wear pink-tinted glasses to block blue wavelength light,” the researchers said.
And if the app prescribes “bright outdoor light” in the middle of the night, a therapeutic lightbox can do the job — yes, its shortcuts sometimes require odd hours.
The study, published in 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.
The app gives users access to these schedules.
How the App Works
Start by entering your typical hours of light and darkness in your current time zone, then choose the time zone you’re traveling to and when, as well as the brightest light you expect to spend the most time in during your trip (indoor or outdoor.) The app then offers a specialized plan and predicts how long it will you take to adjust.
For example, say you’re traveling from Detroit to London, five hours ahead. Your flight leaves at 10 p.m. Eastern Time and arrives at 11:05 a.m. London time the next day. It’s a work trip and you’ll have to spend most of your time in indoor lighting.
Under those circumstances, the app says it can adjust you in about three days. That’s less than the rule-of-thumb one day per hour outside the starting time zone.
The entrainment clock for any trip starts at the beginning of the first light cycle in the new time zone.
So for the London trip, on the day after your arrival, you’d want to get light from 7:40 a.m until around 9 p.m., and not after. Rise earlier on the second day, at 6:20 a.m. Lights out at 7:40 p.m.
You may feel like going for an evening walk, but being in the light at a time when the app prescribes darkness would lengthen the adjustment period, the researchers say.
To get over jet lag most efficiently, researchers recommend:
- Experience one block of light and one block of darkness each day;
- During the light phase, be in the brightest light possible;
- During the dark phase, be in the dimmest light possible. Even a short burst of bright light at the wrong time can extend the time it takes to adjust;
- Dark phases don’t have to be sleep phases;
- If you must be outside during dark phases, block blue light with rose-tinted glasses or a visor. Follow the customized, mathematically optimal schedule offered by the free app, Entrain.
On the third day, get up before sunrise, around 5 a.m. Stay in light until 7:20 p.m. Your body will be synched the following morning. If you veer from the schedule, you can tell the app and it will recalculate going forward.
To show how this new method is different, the researchers illustrate circadian rhythms as a clock with a point at the hour when your body temperature is lowest. This usually occurs about two hours before you wake up.
If the point is usually at 5 a.m. and you travel overseas, it could abruptly swing over to, say, 3 p.m. in your destination. You’re likely to experience jet lag until your system adjusts and your body is once again at its lowest temperature just a few hours before your alarm goes off.
“The way other approaches get these points to line up again is by inching along on the outside of the circle, sometimes pushing you towards and sometimes pulling you away from the target.
“But our schedules can just cut through the middle,” said Olivia Walch, a mathematics doctoral student who built the app. “This is almost like a body hack to get yourself entrained faster.”
Source: University of Michigan