It's estimated that 15 percent of the U.S. work force are shift workers—such as nurses, doctors and other medical professionals, drivers, and police officers—who do not keep a regular 9 to 5 schedule. Shift workers are at significantly increased risk for sleepiness, as well as the common health risks that come with insufficient sleep, such as high blood pressure and heart problems.
Shift work is challenging because it requires people to wake and sleep in a pattern that is out of sync with the body's biological clock. Our internal clock or "circadian rhythm," influences many chemical changes in the body on a 24 hour cycle, naturally telling our bodies to become drowsy in the evening and more alert in the morning, as well as influencing things like appetite and mood. When you have to sleep on an irregular schedule, you're working against your body's clock and you may find it difficult to sleep a full 7-9 hours. You also might find it difficult to be alert and productive if you're working at night, because this is when your circadian rhythm produces sleep-promoting chemicals like melatonin.
Despite the challenges, shift workers need just as much sleep as people who work traditional hours, and even a small amount of sleep loss over time can damage your health or make you unsafe to drive or to carry out work or family responsibilities.