Current perspectives on the function of sleep.

Genuine answers to these questions require some understanding of the function of sleep. How can one say which sleep is most efficient or how much sleep we need unless we know what sleep is supposed to accomplish? Sleep researchers and clinicians can retain some posture of expertise with answers like, "Get enough sleep to keep from feeling sleepy during the day." But this temporizing answer addresses the issue of relieving discomfort, not the issue of need fulfillment. Would we feel comfortable advising patients to "Eat enough to keep from feeling hungry"?