BBC News Online: Sci/Tech

Kneesy answer to jet lag

A wide range of behavioural and physiological functions are governed by circadian rhythms.

Essentially, this is the body's internal clock which roughly follows a 24-hour cycle and relies on light and dark to keep time or to "set".

Because the cycle is not exactly 24 hours long, a daily adjustment has to be made to synchronise to the natural environment.

This is usually achieved through the natural light and dark cycle of day and night.

Many animals have multiple photoreceptors in addition to their visual senses which they use to respond to light in this way.

But in humans and other mammals it has been generally assumed that these non-visual light detectors reside in the eye.

However, scientists at Cornell University at White Plains, New York, say humans have a circadian rhythm photoreceptor on the backs of their knees.

The findings, which have been published by the journal Science, could lead to effective new treatments for sleep disorders and jet lag.

Cornell University's Scott Campbell and colleagues tested the theory on 15 healthy individuals, putting forward or turning back their body clocks in the lab.

Three-hour long pulses of light were shone on the area directly behind the knee.

Shining the light before a certain point in the circadian cycle resulted in a delay.

Light stimulus after this point produced an advance.

The largest shifts, both advances and delays, occurred at times during which people were normally asleep.

"Timed bright light exposure is an effective treatment for sleep and circadian rhythm disorders including jet lag, shift work sleep disturbance, age-related insomnia and advanced and delayed-sleep phase syndromes," the researchers write.

"The finding that the endogenous clock can be manipulated through an extraocular (outside the eyes) route could lead to the development of delivery systems and treatment regimens that may increase the effectiveness of this promising non drug treatment."

Internet Links

Cornell University
Science Online

The BBC is not responsible for the content of external internet sites.

Summaries

In this section

Pollution causing sex change
New alert on millennium computer problem
BBC chief defends online expense
Meet Rama the cama ...
Born to lose
Inquiry into oldest mum birth
Cloned calves could signal major drug development
Boars bothered by bears with sore heads
Test-tube baby is half-boy half-girl
It came from the skies ...
Bat-tening down the hatches
Early retirement for today's PCs
Rift Valley fever: the background