There’s no definite answer to how many hours people should sleep. Although children and teenagers are recommended with certain hours of sleep. Infants need about 16 hours, teenagers need about 9 hours. For most adults, 7 to 8 hours a night appears to be the best amount of sleep. However, many people can get by while others need 10 or more. It all depends on individuals. Also the quality of sleep really matters. How often do you feel still tired and un-rested even though you just got up.
Aging comes with a big problem in sleeping patterns. Many older people get insomnia. They’re unable to fall asleep or stay asleep. However troublesome, it is part of natural aging. Unless it was caused by complications from other health issues, or as a result of medications, there’s no need to worry. As many as half of all people over 65 have frequent sleeping problems. Elderly can’t stay in deep sleep for very long. Sometimes it stops completely.
Source: NINDS