Switch the lights on

Published: Monday 31 August 2009

-- (Credit: SURYA SEN) Exposure for a specific duration cures jet-lag

PEOPLE who fly across time zones spend the first few days on ground in a daze, uncertain whether they should sleep or keep awake. Known as jet-lag, this disturbance in the pattern of sleep can lead to digestive problems, fatigue, disorientation and even mild depression.

Some common remedies suggested include walking barefoot or swimming in the ocean. Standing under the sun is an accepted method but there are variables such as timing, intensity and duration of light, to be considered.

Sleep experts at Brigham and Women's Hospital and the University of Michigan developed a mathematical model which determines the specific duration of light to which a person suffering from jet-lag should be exposed. For the model, the team considered parameters like the background light the person is exposed to while flying, the number of time zones travelled and the person's body temperature.

The team's calculations showed that exposure to light of high intensity (10,000-lux) for a short duration (two hours) or low intensity (3,000-lux) for a longer period (five hours) can help bring a person's body clock back to normal. "This work shows how interventions can cut the number of days needed to adjust to a new time zone by half," said Daniel Forger, from the Center for Computational Medicine and Biology, University of Michigan, usa. He is also an author of the paper published on June 19 in PLoS Computational Biology.

"This model has implications in designing schedules for shift workers or people exposed to environments as in space, under the sea or in the polar regions," said lead author Dennis Dean, from the Division of Sleep Medicine, Brigham and Women's Hospital.

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