Jetlag, that feeling of disorientation and fatigue that occurs when person’s sleep patterns are interrupted, either by shifting time zones or changing from a day-shift to a night-shift, can take days to shake off.
The body eventually readjusts to the new schedule, but this happens slowly, at a rate of around one hour per day.
So-called remedies, ranging from fasting to chamomile tablets, have shown mixed results at best.
But researchers at the Stanford University School of Medicine have shown the use of light therapy can help prepare our biological clocks for the shift.
The body’s sleep cycles are controlled by circadian rhythms, our in-built awareness of day and night, or awake-time versus sleep-time. This biological awareness can be impacted by external factors, one of which is exposure to light.
Jamie Zeitzer, assistant professor of behavioural sciences at Stanford and lead researcher on the paper, has shown that exposure to light during sleep effectively tricks the brain into day-mode, even while a person’s eyes remain closed.
In this small study, published in the Journal of Clinical Investigation, Zeitzer led a team of researchers to reveal the most effective time and frequency of light exposure to recalibrate circadian rhythms.
The study merged 39 adults into a regular sleeping pattern, ensuring the group went to bed and awoke at the same time for two weeks straight. Next, the participants, divided into groups, were exposed to light for an hour before waking – some to continuous light, and some to sequences of flashes at various intervals.
The study showed that two-millisecond flashes of light, every 10 seconds over the course of an hour, was the most effective method to trick the brain into day-mode.
After experiencing this sequence of flashes during sleep, volunteers experienced a two-hour delay in the onset of fatigue.
In theory, light therapy would be applied at the beginning of the hypothetical “morning” of the new schedule. For example, if a traveller is flying to a city where the sun rises two hours earlier that the city they departed from, they would begin their light therapy two hours before sunrise on the day before their flight.
The flashing light is thought to be most effective because periods of darkness between light flashes allow the receivers in the eye to regenerate, and become active again before each light shines.