A group of British and Italian researchers suggest that getting the right amount of sleep each day is vital for a long and healthy life.

While babies need up to 16 hours of sleep a day, teenagers require around 8 hours while adults should get at least six hours of sleep time.
When an adult fails to get the required amount of sleep, the risk of contracting minor and major illnesses increase since the level of immunity goes down. “Sleep debt can be cleared by catch-up naps; people often do that over the weekends. But sleep should be a consolidated episode during the night”, Dr. Himanshu Garg of Medicity, Gurgaon said.
It is also thought that either excess or negligible amount of sleep signals ill health
Source-Medindia