美国国家睡眠基金会称，你的睡眠时间长短很大部分取决于你的年龄。

The National Sleep Foundation suggests that the amount of sleep you need very much depends on your age.

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据美国国家睡眠基金会的一项调查显示，约有三分之二的被研究者在工作日晚上睡眠不足。

According to a survey from the National sleep Foundation, roughly two-thirds of people studied do not get enough sleep on weeknights.

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根据美国国家睡眠基金会，其它症状是：醒得过早、醒来以后难以再次入睡、经常中途醒来、醒来之后疲惫无力。

The others, according to the National Sleep Foundation are waking up early and not being able to fall back asleep, waking often, and waking up feeling unrefreshed.

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