Seven hours sleep enough for teenagers: study

 　　BEIJING, Feb. 21 (Xinhuanet) -- How much sleep do teenagers need? The more, the better? Not really.

　　Researchers from Brigham Young University found that seven-hour sleepers¹ do better academically than their 9-hour counterparts, even though guidelines recommend nine.

　　This study was published in The Eastern Economics Journal.

　　Eric Eide and economics professor Mark Showalter aim to determine what impact sleep duration and quality might have on people's education and health. This study report is the first in a series.

　　They gathered data on 1,724 primary and secondary pupils across the United States. They believed that theirs was a nationally representative sample of schoolchildren.

　　"We're not talking about sleep deprivation². The data simply says that seven hours is optimal³ at that age," said Eric Eide.

　　Apparently⁴, test performance results depend on several factors, but as far as sleep is concerned, more does not necessarily mean better.

　　The study found that sleep schoolchildren require drops with age:

　　· 10-year olds. The optimal amount is 9-9.5 hours each night

　　· 12-year-olds. The optimal amount is 8-8.5 hours each night

　　· 16-year-olds. The optimal amount is 7 hours each night

1 sleepers   

n.卧铺（通常以复数形式出现）；卧车( sleeper的名词复数 )；轨枕；睡觉（呈某种状态）的人；小耳环

参考例句：

• He trod quietly so as not to disturb the sleepers. 他轻移脚步，以免吵醒睡着的人。 来自辞典例句
• The nurse was out, and we two sleepers were alone. 保姆出去了，只剩下我们两个瞌睡虫。 来自辞典例句

2 deprivation   

n.匮乏；丧失；夺去，贫困

参考例句：

• Many studies make it clear that sleep deprivation is dangerous.多实验都证实了睡眠被剥夺是危险的。
• Missing the holiday was a great deprivation.错过假日是极大的损失。

3 optimal   

adj.最适宜的；最理想的；最令人满意的

参考例句：

• What is the optimal mix of private and public property rights in natural resources?私人和国家的自然资源产权的最适宜的组合是什么？
• Optimal path planning is a key link for the sailing contest.帆船最优行驶路径规划是帆船比赛取胜的关键环节。

4 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。