Last month, I went to a conference back East. It was a short trip, four days, and I was jet lagged the whole time. I spent my mornings gulping down hot coffee to help shake off the sleepy haze; in the evenings, when I should have been making up the lost sleep, I was wired, tossing and turning in bed. I could have tried adjusting to East Coast time in the days before I left by getting to bed a few hours earlier and getting up around 4 AM, but that would have required a level of coordination and planning that I'm unlikely to muster in the days before an out-of-town trip.
So I was curious when I learned that a team of Stanford researchers, led by neurobiologist Jamie Zeitzer, PhD, were working on a technique that helps people shift their sleep cycles by flashing light briefly at their eyes while they sleep. They recently published their findings in the Journal of Biological Rhythms.
Beyond the obvious job of vision, our eyes and brain are constantly processing information about the light around us. Light affects our moods and the daily ebb and flow of our biological clocks. It influences when we are sleepiest and most alert. Our brains do a lot of this work behind the scenes and because it happens unconsciously, we are rarely aware of these circadian rhythms - unless something disturbs them, like flying across several time zones.
Zeitzer and his team recruited volunteers and had them get on a routine sleep-wake cycle, going to bed and waking up at the same time every day for about two weeks. The researchers then had the volunteers come sleep in the lab, where the experimental group was given a series brief flashes of light about two millisconds long - about as long as a camera flash - aimed at their eyes. A control group slept in complete darkness, and the volunteers didn’t know which group they were assigned to. The team then measured whether the subjects’ sleep cycle had been affected by measuring the amount of melatonin in their blood. The brain floods the body with melatonin a couple of hours before bedtime and continues releasing the hormone until about an hour after wake time.
The researchers found that the volunteers who got the light flashes were able to shift the sleep phase of their circadian systems. What was surprising was that the intervention did not noticeably disturb the subjects’ sleep. The volunteers in the experimental group didn’t report any less restful sleep than the controls. “This kind of treatment can help people adjust even before they leave for a trip,” says Zeitzer. “Leaving for Australia, the night before you leave, you can adjust a couple of hours. On the plane, you can adjust a couple more. By the time you arrive, you’re already half-way adjusted.”
Besides jet-lagged travelers, this technique could also help teenagers who have a hard time getting up at the right time (a clinical condition for many that goes beyond adolescent laziness) and shift workers. Current treatments for sleep disturbances include sitting in front of bright lights for sometimes hours at a time, which often means it’s only used in extreme cases.
The team is working on shrinking the device, the lab version of which is large and bulky. For a current study with teens who have sleep problems, they've gotten it down to about the size of an outdoor bridge beacon which flashes light in the teens’ rooms at night. Zeitzer is working with a group of post-doctoral scholars and graduate students who hope to commercialize the device once they can get it small enough to fit into an eye mask.
Zeitzer says the team is also juggling with the intervals between the light flashes - shorter intervals of 10 seconds instead of 30 seconds seem to have a bigger effect - and the colors of the light flashes. One ambitious goal he has is to shorten the duration of the flashes a thousand-fold, from milliseconds to microseconds, so short they are imperceptible. “The flashes are so fast, we couldn’t see them at a conscious level, but they would still have an effect on the brain,” he says. “We could use them any time of day, not just when people are asleep.”
For now, his immediate goals are to improve the current system to the point that it can be widely used. He says that it could have a big effect on how we treat sleep disturbances related to light and circadian rhythms. “We can really change how light is used in a therapeutic way,” he says. “How it’s done now is really cumbersome. Because of that, people don’t really do the therapies in the way that they’re supposed to… so [the therapies] aren’t very effective. This kind of technology makes it possible for people to use therapies more effectively.”
Photo by Maarten Visser