Light therapy with a high-intensity light box can help night-shift workers reset their internal clock. That means increasing exposure to morning light if you need to advance your clock, and getting extra evening light if you need to delay it. This type of treatment also helps those with certain other types of sleep disorders. (You can find light-box manufacturers listed on the Web site for the Society for Light Treatment and Biological Rhythms.)

Unfortunately, the process is more difficult, and the effect is less complete for shift work than for sleep disorders. That's because shift work often requires a complete inversion of normal time, and sleep disorders just require a correction of a couple of hours. Meanwhile, as far as the body is concerned, waking up at dusk and going to bed at dawn is entirely unnatural. Even the drive home in daylight at the end of a night shift may be enough to set the body clock back. Some people are never able to fully retrain their rhythms, and the older you are, the more difficult it is to adjust.

Many physicians recommend a combination of light therapy and careful planning to help maximize sleep patterns. For example, shift workers often find it difficult to sleep in the morning when they get off work because the body's natural rhythm fights back, no matter how tired they are. Some physicians recommend that nightshift workers schedule two smaller sleep periods — one in the morning after work, and another longer nap in the afternoon, closer to when the body would be naturally inclined to sleep. It's also helpful to ask friends and family to cooperate by avoiding visits and phone calls during sleep periods, and to take advantage of 24-hour online services as much as possible to complete chores when it won't conflict with sleep.