Children until their midteens need more than eight hours of sleep a night, according to new guidelines for healthy sleep released by a health ministry study group.

The optimum number of hours of shuteye drops off as people age, decreasing to about seven hours at 25, about 6½ hours at 45, and about six hours at 65, according to the guidelines put together by 13 experts.

They note that sleep requirements vary by individual and less is generally needed as the hours of daylight lengthen. Still, they advise: "Try to get as much sleep as you need to avoid becoming sleepy during the daytime."