Combining an experimental light treatment with cognitive behavior therapy has resulted in a sample of teenagers increasing their total sleep time by around 45 minutes a night. The Stanford University study found subtle light flashes in the last few hours of sleep can help adjust an adolescent’s circadian rhythm.
“We have a biological drive to stay awake in the hours before we normally go to sleep,” says Jamie Zeitzer, senior author on the new study. “So our team wondered if we could adjust the circadian timing, having the teens essentially move their brains to Denver while they’re living in California.”
The research team focused on a compelling technique called bright light phototherapy. The idea is that a person’s circadian rhythm can be reset through exposure to extreme bright light in the morning. Even more interesting, however, is the research suggesting this effect can be generated through exposure to millisecond flashes of light in the hours before waking up. These strobe-like flashes are brief, imperceptible and are designed to not wake a sleeping subject.
The first phase of the new Stanford research explored the effect of this kind of flash therapy, without any other behavioral therapy. A number of teenagers were subjected to a four-week experiment involving three-millisecond pulses of light being flashed every 20 seconds across the final three hours of sleep. Half the subjects acted as a control group receiving only three flashes of light every hour, a volume not considered enough to alter circadian rhythms.
This first phase was only mildly successful. The light therapy was found to not significantly cause any sleep disruptions and the subjects reported feeling tired earlier in the evenings. However, the teenage subjects still persisted in staying up later into the night.
“We had to convince teens to try to go to sleep earlier,” says Zeitzer.
So in phase two of the study, the researchers lowered the duration of the light therapy from three hours to two hours, and incorporated several cognitive behavioral therapy sessions, designed to guide the subjects into going to sleep earlier in the evening. The results in this second phase were incredibly positive. Compared to a control group receiving sham light treatment and just the cognitive behavioral therapy, the active treatment group went to bed around 50 minutes earlier, and slept on average 43 minutes longer. The active treatment group was also six times more likely to keep consistent evening bedtimes compared to the control group.
“The cool part, for an intervention teens would potentially have to live with for years, is that it is completely passive,” says Zeitzer. “We set up the flashing light in the person’s bedroom and put it on a timer; they don’t have to wear a device, remember to turn it on, or do anything else.”
The research is undeniably fascinating, suggesting circadian rhythms can be passively reset through light pulses while we sleep. The trial used a custom xenon flash bulb to deliver the pulses, each flicker consisting of 4,000 lux of broad-spectrum white light. It has been hypothesized the flash sequence could be further optimized and the researchers note more recent evidence suggesting flashes every eight seconds instead of every 20 may be more effective.
The underlying mechanism at play is still unknown but the researchers suspect the light flashes are processed by the retina even behind closed eyelids, resulting in subtle manipulations of a person’s circadian system. More research is certainly needed to better understand this mechanism of action, and to further optimize the technique for future therapeutic outcomes, so don't go setting up a night time strobe light in your teenager's room just yet.
The new research was published in the journal JAMA Network Open.
Source: Stanford University