We spend a great deal of our lives sleeping. Infants sleep practically 24 hours a day.
Small children take frequent naps.
Youngsters and teenagers sleep about eight or nine hours each night, while most adults can make do with seven to eight hours, sometimes less. Many elderly people need fewer hours still, perhaps five to six, and also tend to be lighter sleepers. Elderly people may not need to, or be able to sleep as much as younger people. This could be because they lead a relatively inactive lifestyle, or they may also be getting more sleep during the day. The term insomnia refers to an inability to fall asleep or to remain asleep for an adequate length of time.