The need for sleep varies considerably, both from person to person and from one stage of life to another-from an average of 16 hours a day as a baby, to six hours a night in old age.
「睡眠需求」也因人而異，隨著年齡的增加而遞減，從嬰兒時期的每天睡十六個小時，到老年人平均睡六小時，相差甚大。