If you don't sleep well at home, it's usually worse when you travel. And the more time zones a person crosses, the greater the interference with sleep. The natural sleep-wake cycle is actually longer than 24 hours. Studies have shown that a person in a windowless room with no way to know the time gradually lengthens his "day" to 26 or 27 hours, going to bed and getting up later and later. To conform with society's 24-hour day, the biological clock that regulates the sleep-wake cycle has to be reset every day. Changing time zones and going to bed or getting up at irregular times interfere with that process.

If you travel from east to west the "jet lag" effect isn't as great, because the day is lengthened in conformity with the natural tendency of your body clock. Although it takes about a day to get back to normal for each time zone you cross while flying east to west, it takes about twice as long when you fly in the opposite direction. Regestein advises travelers who don't sleep well to begin adjusting to the time at their destination before they take off. The greater the number of time zones you're going to cross, the sooner you should begin shifting your sleep-wake cycle.

One East Coast patient enjoyed making business trips to the San Francisco Bay area and to Dallas, but he was also upset because he "never got a good night's sleep and always felt out of it." When he returned home, he had even more trouble than usual sleeping. Regestein's suggestion helped: Instead of going to Dallas first, reverse the order so that the longest leg of the trip is made with, rather than against, the biological clock. Also, start going to bed later and getting up later a few days before leaving for the West Coast, which is easier if the trip is scheduled for a Monday.

The doctor also got him to break his habit of watching television or reading late into the night while lying in bed, especially in hotel rooms. Insomniacs should associate bed only with sleeping. That requires excluding from bed anything that increases your wakefulness.