Shining Light on Jet Lag

Light therapy prevents jet lag with sequence of flashes, Stanford Medicine study suggests


Many travelers know the frustration of jet lag—the prickly feelings of fatigue and discomfort that often accompany shifting time zones, but new research suggests that light therapy could help prevent jet lag before you ever leave the runway.  

According to a press release issued by Stanford University of Medicine, a new study found that exposing people to short flashes of light at nighttime might prevent jetlag by tricking the brain into thinking it’s a different time than it actually is.

When traveling to new times zones, people’s circadian rhythms are slow to adjust, and they transition only about an hour a day on their own.

The National Institute of General Medical Sciences (NIGMS) says that circadian rhythm is the “physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment.” Jet lag happens when someone disrupts his or her circadian rhythm.

Researchers at Stanford University of Medicine, led by senior author Jamie Zeitzer, PhD, wanted to see if light therapy could trick the brain into thinking it was daytime, even if it was actually night. Dr. Zeitzer is an assistant professor of psychiatry and behavioral sciences at Stanford University.

According to the study, the research team enlisted 39 participants between the ages of 19 and 39, and had them get on regular sleep-wake cycles, waking and going to bed at the same time every day. After two weeks of the same sleep-wake cycles, researchers asked participants to sleep in the lab. The researchers exposed some to an hour of continuous light and others to a sequence of flashes for about an hour.

The study found that the best way to adjust the internal clock was to expose participants to a series of 2-millisecond light flashes, similar to a camera flash, 10 seconds apart. Participants exposed to the flashing method experienced a nearly two-hour delay in experiencing sleepiness. Those who were exposed to constant light only experienced a 36-minute delay in sleepiness.

"This could be a new way of adjusting much more quickly to time changes than other methods in use today," says Zeitzer in the press release.

Current light therapy treatments involve sitting in front of bright lights for several hours during the day to allow the body’s internal clock to transition to a new time zone.

Zeitzer says the reason that the flashing light worked better is partially because the cells in the retina, which transmit light to the circadian system, continue to fire several minutes after the stimulus. Also, the dark breaks in between flashes allow the eye pigments that respond to light to regenerate.

"If you are flying to New York tomorrow, tonight you use the light therapy,” explains Zeitzer in the press release. “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 full study was published February 8 in the Journal of Clinical Investigation. It was funded by the National Heart, Lung and Blood Institute and the Department of Veterans Affairs Sierra Pacific Mental Illness Research, Education and Clinical Center.

The authors disclosed no conflicts of interest.