Feeling groggy after that long-distance flight? Hold the coffee and reach for your mobile phone.
A mathematical tool promises a full recovery in just a few days, even for extreme time zone shifts. While the model has not yet been proven in the real world, a recently released app will let people try it out for themselves.
Your daily activity is usually aligned with your circadian rhythm, a roughly 24-hour cycle controlled by exposure to light and darkness. But a sudden change in schedule caused by travelling to a different time zone can throw off this internal clock.
Timed exposure to bright lights can trigger biological markers associated with sleep patterns, such as levels of the sleep-related hormone melatonin and body temperature. That can help get the body in sync with a new schedule. Previous work on adjusting to jet lag showed that people who experience a 12-hour time shift but forgo light therapy will still be off-schedule after 12 days.
Mathematical models that recommend exposure patterns already exist, and the best current versions require more than a week of carefully adjusting your light exposure to get you over a 12-hour shift.
With help from Kirill Serkh at Yale University, Daniel Forger at the University of Michigan in Ann Arbor used techniques from a branch of maths called optimal control theory to reengineer a model that Forger designed in 1999. "The equations are very hard to solve numerically, that's what has taken so long," he says.
The pair produced more than 1000 schedules for different scenarios, which they say are mathematically proven to beat alternative methods. The updated model prescribes alternating between complete darkness and full daylight, which can be simulated as needed with specialised lamps. The hardest part may be staying in total darkness longer than you might like.
If you have travelled 12 hours from your original time zone and want to start your day at 7 am local time, the model says you must stay in the dark until 1.10 pm on your first day, and then stay in the light until 9.50 pm. The schedule shifts each subsequent day until you are synchronised to your new time zone, which should happen by the fourth day.
The team has just released a free iPhone app called Entrain (http://www.entrain.org) that can do the number-crunching on behalf of a weary traveller. The app recommends optimal schedules and will track how well you are doing, adjusting the pattern if you make a mistake.
"Let's face it, everyone will deviate from the schedules somewhat, no matter how hard they try," says Forger. "We can show you how to adapt."
How well travellers can stick to this kind of schedule in real life depends on the person, says Elizabeth Klerman, a sleep researcher at Harvard Medical School who has designed similar models for adjusting to jet lag. But she says Forger does gorgeous work, and he has built this tool on one of the better, more physiologically accurate models available.
"It becomes a choice: Do you do something inconvenient on the first day to adjust, or do you have jet lag for longer," says Klerman. "At least now you will have the information to decide whether to follow the recommendations and then live with the consequences."
Journal reference: PLoS Computational Biology, DOI: 10.1371/journal.pcbi.1003523
Bonus: sleepyti.me - http://hojja-nusreddin.livejournal.com/3870879.html