Those of you who have ever been on long-haul flights will understand the frustration of jet lag. Now, investigators from the University of Michigan have created an iPhone app that they say offers "shortcuts" to help travelers adapt to different time zones efficiently and quickly.
The researchers of this study, Kirill Serkh and Daniel B. Forger of the Department of Mathematics at the University of Michigan, recently published the details of their creation in the journal PLOS Computational Biology.
Jet lag is a feeling of tiredness and confusion following an aircraft journey. Since our internal body clock is set to a regular rhythm of daylight and darkness exposure, it can be difficult to adapt to differences in such exposure, and our sleep-wake patterns become disrupted.
Such disruption to sleep patterns has been associated with numerous health conditions. Earlier this year, Medical News Today reported on a study suggesting disrupted sleep can speed up cancer, while more recent research found that onset of Alzheimer's could be triggered by sleep disturbances.
The more time zones a person crosses, the more severe jet lag can become. The condition can affect mood, physical and mental performance, the feeling of hunger, digestion, bowel habits, urine production, body temperature and blood pressure.
To help overcome jet lag, medical professionals recommend taking short naps after arriving at a destination and drinking plenty of water. But according to the University of Michigan researchers, jet lag is a "mathematical problem" that can be solved with their new iPhone app, called Entrain.
How does Entrain work?
Entrain works by helping to regulate the internal body clock through custom schedules of light and dark. The app lets a person know when they should be exposed to the brightest light possible and when they need to be exposed to a dark environment.
The new Entrain iPhone app could help travelers adapt to new time zones much quicker.
It calculates light adjustment schedules by using two mathematical models that have been shown to accurately describe circadian rhythms in humans. These equations, in combination with a method called optimal control theory, can work out schedules for over 1,000 flight paths.
To work out a light schedule when traveling, the user must input their usual hours of exposure to light and dark in their current time zones. They then choose the time zone they are traveling to and the time of travel.
Additionally, the user must enter the brightest light they expect to spend most of their time in throughout their trip - indoor or outdoor.
The app will then offer the user a personalized light adjustment schedule and inform them of how long it will take to get used to the new time zone.
The researchers use an example to explain how the app works: the user is traveling from Detroit in the US to London in the UK - a time zone that is 5 hours ahead. Their flight departs at 10 pm Eastern Time and arrives at 11:05 am London time. The user is in London for work, so they will be spending the majority of their time in indoor lighting.
In this situation, the app will inform the user that they will adjust to the new time zone in around 3 days. The researchers say the usual "rule-of-thumb" for the time it takes to recover from jet lag is one day for every hour outside of the original time zone. Therefore, the team says the app can significantly reduce jet lag recovery time.
Commenting on the new app, Forger says:
"Overcoming jet lag is fundamentally a math problem and we've calculated the optimal way of doing it.
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."
Is it easy to stick to the light adjustment schedule?
According to the researchers, adjustment of the internal body clock will begin at the start of the first light cycle in the new time zone.
Using the example of the Detroit to London trip, the investigators say that on the day after arrival, a person would need to be exposed to daylight from around 7:40 am until 9 pm. The day after that, they would need to expose themselves to daylight earlier, at 6:20 am, and venture into darkness at 7:40 pm. On the third day, they would need to rise at 5 am and remain in daylight until 7:20pm.
Sticking to this schedule means the internal body clock would be readjusted by the following morning, and veering off this regime will extend adjustment times.
But how realistic is it to stick to such schedules?
The researchers admit that at times, the app will recommend a person to expose themselves to daylight and darkness at odd hours. But they say if a user needs to go outside when they are meant to be in the dark, wearing pink-tinted glasses will block the "blue wavelength light" that is likely to disrupt their body clock. And for the reverse - if a user is required to be exposed to daylight in the middle of the night - they say a lightbox will do the job.
Not only could the app help those of us who endure long-haul flights for business and pleasure, the researchers say it could help improve the health and quality of life for pilots and flight attendants, as well as shift workers.
"We also hope that methods similar to the ones presented here could be used to study other problems of optimal perturbation of biological oscillators, including those that regulate breathing or heart rhythms, or potentially to ecological or environmental problems on larger scales," they conclude.
The Entrain app is now available to download free for iPhones from the Apple Store.
Medical News Today recently reported on a smartphone app that the creators say can reduce stress for people who have anxiety.