What does Harvard Medical School say?
While sleeping well is no guarantee of good health, it does help to maintain many vital functions. One of the most important of these functions may be to provide cells and tissues with the opportunity to recover from the wear and tear of daily life. Major restorative functions in the body such as tissue repair, muscle growth, and protein synthesis occur almost exclusively during sleep.
Many other conclusions about the role sleep plays in maintaining health have come from studying what happens when humans and other animals are deprived of the sleep they need. For example, scientists have discovered that insufficient sleep may cause health problems by altering levels of the hormones involved in such processes as metabolism, appetite regulation, and stress response. Studies such as these may one day lead to a better understanding of how insufficient sleep increases disease risk.
In the meantime, sleep experts say there is ample evidence that shows that when people get the sleep they need, they will not only feel better, but will also increase their odds of living healthier, more productive lives.