Light is important for our sense of well-being. In fact,light influences brain function, impacts circadian rhythm, as well as sleep and sleep and arousal. We have evolved to have our physiology and behaviour rhythms consistent with our light dark cycles.The way in which we do this is that we actually synchronize with our retina photoreceptors in our retina. If our circadian rhythm -- our so called day-to-night clock -- is off, it can impact the following:

  • thermoregulation
  • cardiovascular function
  • immunity
  • sleep
  • vigilance
  • memory
  • cognition

We know that light resets melatonin production,which is critical for our circadian rhythm. The researchers in this study sought to find out if exposure to night light and different kinds of exposure could influence our clocks.Light therapy works best at night because the body's circadian rhythms, which control sleep cycles, are more sensitive to light at night-- even through closed eyelids.The researchers found that short flashes of light at night are more effective than continuous light exposure and this could further speed up the process of adjusting to a different time zone before a trip.

The transfer of light through the eyes to the brain does more than provide sight. It also changes the biological clock and a person's brain can be tricked into adjusting more quickly to disturbances in sleep cycles by increasing how long he or she is exposed to light prior to travellingto a new time zone.

We do know that after arriving in a new time zone, the body will eventually adjust on its own but at a slow pace of about one hour a day.Meanwhile, jet lag, which occurs because your body's clock is still synced to your original time zone, can cause fatigue, lack of alertness, a general feeling of malaise and sometimes gastrointestinal problems.

The authors point out that light therapy is designed to speed up the brain's adjustment to time changes. By conducting light therapy at night, the brain's biological clock gets tricked into adjusting to an awake cycle even when asleep. The authors called it a kind of "biological hacking" that fools the brain into thinking the day is longer while you get to sleep

The study found that a sequence of 2-millisecond flashes of light, similar to a camera flash, 10 seconds apart elicited a nearly two-hour delay in the onset of sleepiness. It was the most efficient and fastest method of adjusting the internal clock rather than participants exposed to continuous light, the delay was only 36 minutes.

Two bits of physiology explain why flashing lights work better than a continuous light:

1.    The cells in the retina that transmit the light information to the circadian system continue to fire for several minutes after the stimulus -- in this case, flashing light -- is no longer there

2.    The gaps of darkness between the light flashes allow the pigments in the eye that respond to the light to regenerate -- that is, go from an inactive form that cannot respond to light to an active form that is able to respond to light

We will have to wait and see where the research takes us and if such units will come to market but flashing-light therapy used at night could be a great method of helping to adjust the internal biological clock for all kinds of sleep cycle disruptions -- from medical residents whose sleeping schedules are constantly changing, to night-shift workers who want to be awake during daylight hours on the weekends, to sleepy truck drivers whose sleep schedules are constantly changing.