These help explain how people experience jet lag when their internal circadian rhythms get out of sync, while also having wider implications for disorders ranging from insomnia to depression to heart disease.
Chronobiology, or the study of biological clocks, is now a growing field of research thanks to the pioneering work of the three scientists, who explained the role of specific genes in keeping animal bodies in step with light and darkness.
Today scientists are exploring novel approaches to new treatments based on such circadian cycles, including establishing the best times to take medicines, and there is an increased focus on the importance of healthy sleeping patterns.
"This ability to prepare for the regular daily fluctuations is crucial for all life forms," Thomas Perlmann, secretary of the Karolinska Institute Nobel Committee, told reporters.
"This year's Nobel prize laureates have been studying this fundamental problem and solved the mystery of how an inner clock in our bodies can anticipate daily fluctuations between night and day to optimise our behaviour and physiology."
Rosbash said the news that the trio had won the Nobel prize, which is worth 9 million Swedish crowns ($1.1 million), was "a little overwhelming".
"It took my breath away, literally. I was woken up out of deep sleep and it was shocking," he told Reuters.
Scientists were already pondering the concept of body clock genes in the 1960s and 1970s.
Then in the mid-1980s the three laureates used fruit flies to isolate a gene that controls the normal daily biological rhythm and showed how it encodes a protein that accumulates in the cell during the night and degrades during the day.
Further research revealed the role of other genes in the complex system. Now doctors are paying increased attention to the implications of this daily cycle in people who have erratic sleeping and working patterns or in children who stay up late.
"We are learning more and more what impact it has to not follow your clock," Nobel committee member Christer Hoog told Reuters. "If you constantly disobey your clock, what will happen? Medical research is going on with regards to that."
Medicine is the first of the Nobel Prizes awarded each year. The prizes for achievements in science, literature and peace were created in accordance with the will of dynamite inventor and businessman Alfred Nobel and have been awarded since 1901.
Nobel medicine laureates have included scientific greats such as Alexander Fleming, the discoverer of penicillin, and Karl Landsteiner, whose identification of separate blood types opened the way to carrying out safe transfusions.
The prize has not been without controversy, especially with the benefit of hindsight, such as the 1948 award for the discovery of DDT, a chemical that helped battle epidemics but was later banned due to its harmful environmental impact.
(Additional reporting by Scott Malone, Anna Ringstrom, Simon Johnson, Daniel Dickson, Helena Soderpalm and Johannes Hellstrom; Editing by Gareth Jones)
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