A newborn baby may sleep as much as 18 hours a day, while a middle-aged executive may manage on as few as 5 hours. But how much is healthy and how much do we need? The short answer is that there is no answer: your needs depend on your age and gender, and it varies between individuals.Young animals generally sleep more than adults and humans are no exception. The structure and intensity of sleep is different too. In young people there is a preponderance of REM sleep, and non-REM sleep is very deep, probably to aid brain maturation.
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