Very brief exposure to light flashes while sleeping can help reset the body’s circadian clock and may prove to be an effective strategy for managing phase shift sleeping disorders.
Light flashes at levels of just 50 lux for 10 μsec every 15 sec induced phase shifts reaching 90% of maximum, reported Jamie Zeitzer, PhD, of Stanford University in California, from a study of 56 healthy young men and women.
The effect was not increased when the flash duration was lengthened to as much as 10 sec, Zeitzer said at SLEEP 2019, the annual joint meeting of the American Academy of Sleep Medicine (AASM) and the Sleep Research Society (SRS).
Previously, Zeitzer’s lab had found similar results with flashing light therapy, with a greater magnitude of effect than with continuous light. The current study was aimed at determining how low the flash brightness and duration could go while maintaining the effect.
During the first 14 days of two 16-day parallel studies, participants were asked to maintain a regular sleep/wake cycle — confirmed through actigraphy and sleep logs — to establish circadian phase stabilization.
Then, for the last 2 days, participants slept in specialized time-isolation labs, and circadian pacemaker phase was determined via salivary melatonin onset.
Light exposure occurred the first night in the sleep lab. Participants were forced awake 2 hours after their pre-established regular bedtime and exposed to 1 hour of flashes, delivered at 15-sec intervals.
Flashes of only 8 lux were enough to induce half the maximum phase shift, Zeitzer reported. For context, bright sunlight is about 100,000 lux; outdoor light dips to about 10 lux at twilight. Elevators are typically illuminated at roughly 100 lux.
In an interview with MedPage Today, Zeitzer said the flash light technique has the potential to be an effective therapeutic strategy for any sleep problems related to disruptions in circadian rhythm.
Common phase shift disorders include delayed sleep phase syndrome, characterized by the inability to get to sleep until very late at night; and advanced sleep phase syndrome, characterized by going to sleep very early in the evening and waking earlier than desired.
Current therapeutic strategies for these and other sleep phase disorders are often not terribly effective, Zeitzer said, because they rely on changing patient behavior.
“Anytime you require people to change behaviors there are going to be issues with compliance,” he said. “If we can deliver therapy during sleep, you take behavior out of the equation.”
Zeitzer and colleagues recently completed a preliminary study of the light flash stimulus in teenagers.
He explained that since teens have a biological drive to go to bed later, even a slight phase shift may have a big impact.
The teens in the study received the light flash stimulus nightly, two hours before they were scheduled to wake up. The goal of the stimulus was to reset to teens’ body clocks so that they would naturally feel sleepy about an hour earlier than normal.
“You can get bigger phase shifts, but we didn’t think it was realistic to think that a teen who normally goes to bed at 1 [a.m.] would go to bed at 10:30 [p.m.],” he said.
Funding for this research was provided by the Department of Defense.
Zeitzer reported no relevant relationships with industry related to this study.
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