Jet Lag

In today?s world, catching a flight to Tokyo or Delhi to do business has become commonplace. But frequent air travel through many time zones may not be healthy. A new study in Current Biology relates frequent shifts in the light-cycle to increased mortality in mice. A circadian rhythm is regular internal clock in the body that controls many of our functions. In humans, the cycle is roughly a 24-hour one. While circadian rhythms are set internally, they can be influenced by external cues such as sunlight and temperature. Circadian rhythms are important in determining the sleeping and feeding patterns of all animals, including human beings. At different part of the cycle, differences in brain wave activity, hormone production, cell regeneration and other biological activities have been noted. Researchers studied the response of 3 groups of genetically engineered old and young mice to changes in their circadian rhythms. The old mice were the equivalent of a 70-90 years old human. Each group contained both old and your mice. Through changes in light, the first group had their internal clocks moved forward by six hours each week- simulating flying from New York City to Western Europe. The second group had their clocks put back by six hours each week. And the third group did not face any time changes. The effect of light-shifting was striking in terms of the lifespan of older mice. Only 47% of older mice survived regular forward shifts, and only 68% of older mice survived regular backward shifts. This compared to 83% of older mice surviving if no changes were made in their clocks. The effect of shifting light cycles had no effect on the young mice. While it is important to remember that these results are in mice and not humans, previous research has linked heart disease and breast cancer to shift work that throws off ones sleep patterns.