Three US geneticists - Jeffrey Hall, Michael Rosbash and Michael Young - have been awarded the Nobel Prize for medicine for shedding light on the biological clock that governs the sleep-wake cycles of most living things.



The team's work revealed the role of genes in setting the "circadian clock" which regulates sleep and eating patterns, hormones and body temperature, the Nobel committee said in announcing the prize on Monday.

"Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronised with the Earth's revolutions."

All life on Earth is tuned to the rotation of our planet. Scientists have long known that living organisms, including humans, have an internal timekeeper that helps them anticipate and adapt to the rhythm of the day.

Hall, 72, Rosbash, 73, and Young, 68, "were able to peek inside our biological clock and elucidate its inner workings", the jury said.

The three scientists will share the prize of nine million Swedish kronor (about $1.1m or 937,000 euros)

They identified genes that regulate the clock, and the mechanism by which light can synchronise it.

Circadian dysfunction

A disrupted circadian clock is what causes jetlag - which happens when the internal clock and external environment move out of sync as people rapidly change time zones.

The clock also regulates sleep, which is critical for normal brain function.

Circadian dysfunction has been linked to depression, bipolar disorder, cognitive function, poor memory formation and some neurological diseases.

Studies have indicated that a chronic misalignment between a person's lifestyle and the circadian clock - when doing irregular shift work, for example - might be associated with an increased risk for neurodegenerative diseases, metabolic disorders and inflammation.

Disruptions to the circadian clock can have serious consequences ranging from impulsive behaviour to life-threatening conditions such as obesity and cancer, the experts say.



One need only to look at the poor health records of shift workers such as nurses or factory labourers.



The World Health Organization has already raised the red flag, with a 2007 report noting that "circadian disruption" is "probably carcinogenic" - which means cancer-causing.

Scientists are working hard on methods to alter the rhythm of errant clocks as a means to "improve human health", the Nobel jury said.

The period gene

Using the fruit fly as a model organism, this year's laureates isolated a gene that controls the daily biological rhythm, called the period gene.

"They showed that this gene encodes a protein that accumulates in the cell during the night and is then degraded during the day," the Nobel statement said.

"Subsequently they identified additional protein components of this machinery, exposing the mechanism governing the self-sustaining clockwork inside the cell."

When workers force themselves to stay awake, it triggers the release of stress hormones such as cortisol - the same one that rushes into your blood in a life-or-death situation.

The chemicals may keep a person awake, but there are significant side effects.

For example, cortisol works to suppress the immune system and, in the long run, can make a person more susceptible to a range of illnesses.

Such a lifestyle also opens one up to eating outside of normal times, when the body's metabolism might be lower and the calories are more likely to be converted into fat instead of being burned up.

Even short-term disruptions of the circadian clock can wreak havoc on the human body, such as jetlag.

Flying from Paris to Los Angeles deposits travellers nine hours earlier in time, upending eating and sleeping patterns.

The results can be blunted interaction with the world and a lack of empathy, complex thinking, or even clear memories.

In such a state, people can do "overly impulsive things - jump the red traffic light and fail to see the consequences of actions".

Curiosity for medicine

Rosbash, born in 1944 in Kansas City, Missouri, to parents who had fled Nazi Germany, received his doctoral degree in 1970 at the Massachusetts Institute of Technology, and has since 1974 been on faculty at Brandeis University, where he worked closely with Hall on his prize-winning research.

Hall had originally planned to attend medical school when he entered Amherst College in Massachusetts in 1963, but halfway through his bachelor's degree, his curiosity for medicine was replaced by one for basic science.

He went on to earn his doctoral degree in 1971 at the University of Washington, before joining Brandeis University in 1974. He is now retired.

Young received his doctoral degree from the University of Texas in Austin in 1975 and has been on the faculty at Rockefeller University in New York since 1978.