Narrator: This is Science Today. According to the U.S. Department of Labor Studies, about 15 million American workers regularly work a night shift. Aside from problems with insomnia or trouble staying awake, some studies suggest that working the night shift is associated with other problems, including cancer, heart disease and depression. Researchers say the reason may be the disruption of our precisely-timed internal clock, or Circadian Rhythm.
Kriegsfeld: They're synchronized to exactly twenty-four hours and this is important for normal functioning because every physiological or biochemical process in your body is best carried out of the particular time of day or night and if your internal clock is not synchronized with the external environment, then your body will be performing these tasks at the incorrect time of day.
Narrator: Lance Kriegsfeld of the University of California, Berkeley says women's health can be particularly affected.
Kriegfeld: Often night shift workers have reported difficulty becoming pregnant and when they do become pregnant, it's often difficult to maintain the pregnancy. If these hormones aren't secreted at the proper time of day, then the reproductive axis doesn't work properly.
Narrator: For Science Today, I'm Larissa Branin.