The need for sleep varies considerably from person to person.

不同的人对睡眠的需要差异相当大。

《牛津词典》

If you are going to sleep, you need yo put on your pajamas.

如果你要睡觉的话，那就把睡衣穿上。

youdao

I find that I need very little sleep these days.

我觉得我现在需要的睡眠很少。

《柯林斯英汉双解大词典》

Yet sleep scientist Ying-Hui Fu at the University of California, San Francisco,says little is known about the basic need for sleep.

VOA: special.2009.08.26

Studies have shown that over time, most humans need eight to eight and a half hours of sleep for the best health.

VOA: special.2009.08.26

But here is something that scientists now know: A team led by Professor Fu has reported the first genetic link to how much sleep we need.

VOA: special.2009.08.26

After many years of study, no one knows how much sleep we need to function normally.

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He adds the app can't be used to cut back on the sleep you need just to wake you up at the right time when you are already rested.

WSJ: Smart Alarms Decide When You Should Really Wake Up

The important thing, says Scharf, is that people who need sleep aids can take them.

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