How new therapy sheds light on jet lag



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Air travel is an increasing part of everyone's life but the effects of a long journey can really mess things up for the first day or two. Now, a new study at Stanford University School of Medicine suggests exposure to short flashes of light while sleeping could provide a fast and efficient method of preventing jet lag.


Clocking in

A team of researchers at Stanford, including Drs. Jamie Zeitzer and Raymond Najjar, have been working on a way of using light to help people adjust more quickly and easily to changes in their sleep cycles. Currently, light-therapy for disruptions in sleep patterns means sitting in front of bright lights for prolonged periods during the day. Though this allows travelers to adjust their body clocks to a new time zone in small steps prior to taking a trip, it's not always the best fit for a busy schedule.

In the new study, Zeitzer and Najjar found that exposing participants to short flashes of light at night is more effective than continuous light exposure and could speed up the process of adjustment."This could be a new way of adjusting much more quickly to time changes than other methods in use today," said Zeitzer, assistant professor of psychiatry and behavioral sciences and senior author of the study — published online in the Journal of Clinical Investigation.


Zoning out

When light hits the eyes, it does more than allow us to see — the changing patterns of night and day also control the body's biological clock. Scientists found the brain can be tricked into adjusting to disturbances in sleep cycles by increasing how much light it is exposed to before traveling to a new time zone. In addition, an earlier study has shown that light therapy is more effective at night because the body's circadian rhythms — which control patterns of wakefulness and sleep — are more sensitive to light at night, even through closed eyelids.

The body can adjust to a new time zone by itself but it's a slow process: about one hour a day. This "lag" as your body catches up is familiar to many who take long journeys by air over different time zones. With your body still tied to the original time zone, the patterns of the body are out of sync, at odds with the light patterns at his or her destination, and the traveler can experience fatigue, dulled senses and even gastrointestinal problems.


Trick cycle

The researchers took 39 participants, aged between 19 and 36, who had had regular, stable sleep routines — waking and retiring at regular times every day — for two weeks. After this, they were invited into the controlled environment of a sleep lab. Here, some were exposed to continuous light for an hour and others were exposed to a sequence of flashes of various frequencies for an hour.

The new light therapy is designed to speed up the brain's adjustment to time changes. By conducting light therapy at night, the brain's biological clock gets tricked into adjusting to an "awake cycle" even when asleep. This "biological hacking," Zeitner says, fools the brain into thinking the day is longer while you get to sleep. The team found that those exposed to the light flashes — a sequence of 2-millisecond flashes of light, similar to camera flashes, 10 seconds apart experienced a delay in the onset of sleepiness of almost two hours. Participants exposed to the continuous light only gained a 36-minute delay.


News flash

There are two reasons flashing lights are more effective than continuous ones, says Zeitner. "The first is that the cells in the retina that transmit the light information to the circadian system continue to fire for several minutes after the stimulus is no longer there. The second is that the gaps of darkness between the light flashes allow the pigments in the eye that respond to the light to regenerate — that is, go from an inactive form that cannot respond to light to an active form that is able to respond to light."

Zeitzer sees potential for long-distance passengers like those on the haul over to the east from California: "If you are flying to New York tomorrow, tonight you use the light therapy," he says. "If you normally wake up at 8 a.m., you set the flashing light to go off at 5 a.m. When you get to New York, your biological system is already in the process of shifting to East Coast time." The research shows most people have no problem sleeping through flashing lights, Zeitner says, and could also prove useful for those with irregular or shifting sleep patterns, like shift workers and medical students.