Jet lag treatment helps clear the fog

For many travelers, the hardest part of crossing time zones is getting over jet lag. According to a new study, a promising kind of treatment could leave you rested and refreshed in the time it takes to turn on a light.

The treatment is a machine that emits an extremely brief flash of light. Researchers from Stanford University Medical Center in the U.S. recruited 39 volunteers who were placed on a strict two-week schedule in which they went to bed at the same time each night and set their alarm to wake up at the same time each morning. Then, the volunteers moved into a sleep lab. At the bed time the volunteers established during the preceding two weeks, the researchers exposed half the volunteers to continuous light for an hour, and exposedthe other half to a sequence of flashes of light at various frequencies also for an hour. Those treated with continuous light were able to stay awake foran extra 36 minutes past their bedtime.

The study is published today in the Journal of Clinical Investigation.

However, if instead they got two x two millisecond flashes of light 10 seconds apart, they could stay up two hours past their bedtime. Two extremely brief pulses of light had that profound an effect. Best of all, no medications were needed.

Researchers have long known that light does more than enable us to see; it resets the body's biological clock. Light that reaches the cells in the retina send signals along nerve pathways to the part of the brainthat control our circadian rhythm. In effect, the light tricks the brain into adjusting more quickly to the disturbance in sleep-wake cycles when you cross time zones during a long-haul flight.

The flashing lights are thought to be mosteffective for two reasons. First, though the flash of light is only two milliseconds in duration, the cells in the retina that are activated by the flash continue to fire for several minutes afterwards. In other words, you don't need longer duration light to activate the system. Second, during the darkness following the first flash, other cells in the retina are recruited; by the time the second flash occurs, these additional cells also fire, thusamplifying the response and giving the brain a bigger time shifting jolt.

Best of all, the flashes of light do not seem to wake patients up. The pulse of light is so brief that it's not long enough to disturb sleep. The researchers found that most of the subjects theyevaluatedin this and other studies were able to sleep through the flashing lights without waking up. And there's little risk that the light itself will wake the patient up. That's becauselight blue spectrumpulsed flashescan penetratethe retina through closed eyelids. Patients use a sleep mask that provides narrowband blue light pulses.

In a study not connected to researchers at Stanford, participants said the sleep mask woke them up on the first night of light treatment, but that by the third night, they had become used to it. Some subjects continued to wake up at the first pulse of light, but would immediately fall back asleep, while others slept soundly through the light pulses. Rapid Eye Movement or REM sleep was not affected.

Here's how you might use it. Say I'm flying east across five time zones from Ontario and Quebec to London or Paris. The time there would be five hours ahead. So, if I usually wake up at 7 am Eastern Time, to adjust to being London or Paris, I have to adjust my wake up time to 7 am GMT or 2 am ET. The night before I fly out, I would set the light flashingmachine to emittwo flashes ten seconds apartat exactly 2 am or five hours before my usual wake time. By the time I have my first sleep in London or Paris, I wouldn't be completely adjusted, but I'd be well on the road.

Assuming the technique is validated in more studies, flashing light therapy could also help anyone who does shift work and has trouble adjusting to a string of night shifts. That would include paramedics, police, firefighters,air traffic controllers, and ER physicians like me. Researchers also say the therapy should also help anyone whose duties mean they have to be awake for long stretches. That would include long haul truck drivers. It would also include doctors on call. I could imagine obstetricians and midwives using it to stay awake at night when they have a woman in labor. It would help astronauts on long space missions. And most of all, it would help commercial pilots, flight attendants and anyone whose job forces them to fly each week across time zones.

A commercially available version of the light emitter should be on the market in a year or two.

Safe and wakeful travels.

House doctor Brian Goldman isthe host of CBC Radio's White Coat Black Art.