How the Body Works: Sleep Requirements

According to their sleep requirements, a group of people, between the ages of twenty and thirty-four, were classified as short-period and long-period sleepers. The average time each group spent asleep, and the type of sleep it was, is shown by the length of the tube. The percentage of total time per night spent in each type of sleep is indicated in the segmented circles. Both types had the same amount of slow-wave sleep, but the long sleepers had almost twice as much dreaming sleep.