Most people need eight hours' sleep every night. Scientists have found that people who sleep for less than six 小题1:            a half hours a night are more often ill than people who sleep for eight hours. People who sleep for less than five hours often die young, and do less well 小题2:            work. Sleep is really important to people's lives. Good 小题3:            needs good sleep.

"But not too much of it," says Professor Jim Home of Loughborough University. "Sleep is like 小题4:            and drink. You would always like to have a little bit more,  but that doesn't mean you need it." He found that people who sleep for more than 小题5:            hours a night die younger than people who usually sleep for seven or eight!