Flashing light during sleep staves off jet lag & may not wake you – study

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Although seeing the world can be a hugely rewarding experience, it often comes with an unwanted consequence: jet lag. But a new study says there may be a way to combat tiredness – by exposing yourself to flashes of light as you sleep.

The research, led by Dr. Jamie Zeitzer of Stanford University Medical Center, studied 39 volunteers aged 19 to 36 who were given a routine sleep-wake cycle for two weeks. That is, they had to go to bed and wake up at the same time every day.

As they slept, the participants were exposed to light therapy. Some were given various frequencies of flashing light for an hour, while others were given continuous light for the same amount of time.

Described by Zeiter as a sort of “biological hacking," light therapy triggers signals from the retina to the circadian system in the brain, which alters the body's biological clock. This results in the body clock being tricked into adjusting to an awake cycle, even when it's asleep.

The researchers found that bursts of light lasting two milliseconds – similar to a camera flash – set off at 10-second intervals delayed the onset of sleepiness the next day by nearly two hours. The delay for those exposed to continuous light was just 36 minutes.

The flashing light is believed to work better for two reasons. Firstly, “the cells in the retina that transmit the light information to the circadian system continue to fire for several minutes after the stimulus — in this case, flashing light — is no longer there,” according to Zeitzer, an assistant professor of psychiatry and behavioral sciences.

Secondly, the gaps of darkness between flashes allow the pigments in the eye that respond to light to regenerate. In other words, they are able to “go from an inactive form that cannot respond to light to an active form that is able to respond to light,” Zeitzer said.

The therapy “could be a new way of adjusting much more quickly to time changes than other methods in use today,” Zeitzer said, adding that the team has “found that most people can sleep through the flashing light just fine.”

The researchers believe light therapy could also be used for reasons other than jet lag – including for night-shift workers and people whose sleep schedules are constantly changing.

Zeitzer and his colleagues are now testing the technique for longer periods of time and multiple nights. They are also conducting a trial with around 50 teenagers to determine whether light therapy can help students get more sleep at night. This is because teenagers' circadian clocks typically get delayed around puberty, making them feel sleepy later at night.

“We’re basically looking to intentionally jet lag teens so that they can go to bed at a reasonable time,” The Wall Street Journal quoted Zeitzer as saying.

They are also working with the company LumosTech to develop a device resembling a sleep mask which would allow customers to use flashing light therapy through a smartphone app.