Flashes of light against jet lag

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It happens again and again when the time changes, but also on long-haul flights - the internal clock gets mixed up. Fatigue or exhaustion are just two possible side effects. But “biological hacking” of the biological clock could be possible with short flashes of light.

Jet lag can vary in severity from person to person: You cannot fall asleep in the evening, you cannot get out of your feathers in the morning, and your digestion gets mixed up. Some are also unfocused or react more slowly. This is a constant nuisance for those who have to fly often or work in shifts. Scientist Raymond Najjar from the Singapore Eye Research Institute has found a new starting point to remedy this: the retina. It has long been known that the photoreceptors on the retina are not only there to see, but also influence the internal clock.

Unnoticed thunderstorm

To do this, he had 39 subjects spend one night in the sleep laboratory. The test subjects had previously paid attention to a very regular sleep-wake cycle for two weeks. In the laboratory, Najjar exposed the study participants to light stimuli for one hour shortly after they fell asleep. Group one was irradiated with a bright continuous light, group two with short flashes of light of two milliseconds each. In between there was ten milliseconds of darkness. The test subjects were not aware of the effects of light - they continued to sleep quite normally. The next day, the level of the sleep hormone melatonin in the saliva of the test subjects was determined, and Najjar also determined when the test subjects became tired in the evening.

The flashes of light proved to be effective: the test subjects who were flashed on became tired an average of two hours later than on the previous days. Their melatonin concentration also rose more slowly and later. The continuous light, on the other hand, had no measurable effect on the bio-clock.

Tricked brain

"The flashes of light could open up a new way to quickly adapt to time differences," says senior author Jamie Zeitzer of Stanford University. It is a simple and risk-free way to prepare for a long-haul flight. Because normally our internal clock can only change around an hour a day. There are still no drugs against jet lag. Melatonin has been tested in various studies, but the results have been inconsistent - it helped some and not others.

Behind the "biological hacking", as Zeitzer calls it, is apparently that you can trick the brain with the flashes of light.Because light is the most important clock for the internal clock. It is registered by the photoreceptors on the retina - even when the eyes are closed. The receptors get used to the continuous light very quickly and then no longer send any signals to the thinking organ. The fast, bright flashes, on the other hand, always provide new stimuli. In this way, the brain can be led to believe that it is still daytime, even when one is asleep.

The light flash therapy could not only help people with jet lag, but also be useful for shift workers, according to the researchers. This would allow them to get used to the shift in their wake-sleep rhythm more quickly.

Source: Raymond P. Najjar and Jamie M. Zeitzer: Temporal integration of light flashes by the human circadian system, J Clin Invest. 2016. doi: 10.1172 / JCI82306.

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