A genetic mutation that allows people to feel fully rested with fewer than six hours sleep anight has been identified by studying a family who get by on less than average. It is thesecond such finding in recent months.

　　科学家通过对一个家庭的研究，发现了一种可以使人在每晚睡眠不足6小时的情况下得到充分休息的基因突变。这个家庭的成员每日睡眠时长低于平均水平。这是近几个月来第二个针对这一问题的同类发现。

　　Ying-Hui Fu at the University of California, San Francisco, and her colleagues have been seekingout and studying families in which some people seem to need less sleep than normal. Theyhave been looking for the gene variants that might be responsible, and geneticallyengineering these variants into mice to confirm their effect.

　　加州大学旧金山分校的傅嫈惠和她的同事们一直在寻找和研究那些所需睡眠少于平均水平的家庭。他们一直在寻找可能起作用的基因变异，并通过基因技术将这些变异的基因植入老鼠体内以证实其作用。

　　Her team has found several mutations make people need less sleep. In August, Fu's teamreported that a mutation in a gene called ADRB1 allows 12 members of a family to sleep aslittle as 4.5 hours per night without feeling tired. This gene codes for a receptor proteincommon in a brain region called the dorsal pons, known to regulate sleep.

　　她的团队已经发现了几种基因突变会使人们需要更少的睡眠。今年8月，傅嫈惠的研究小组报告称，ADRB1基因突变使一个家庭的12名成员每晚只睡4.5小时而不会感到疲劳。这种基因为一种受体蛋白编码，这种蛋白在大脑中的脑桥背侧区域很常见，这一区域负责调节睡眠。

　　Now the team has found a mutation in a gene called NPSR1 in another family in which somepeople report feeling fully rested after much less sleep than average. Of the two members ofthis family whose sleep habits they studied, one averaged 5.5 hours a night and the other just4.3 hours.

　　现在，研究小组在另一个家庭中发现了NPSR1基因突变，一些家庭成员报告说，他们在睡眠时间远远少于平均水平的情况下，仍然感到精力充沛。他们研究了其中两名家庭成员的睡眠习惯，一人平均每晚睡5.5小时，另一人仅睡4.3小时。

　　NPSR1 codes for a protein receptor in the brain known to be involved in arousal and sleepbehaviour. When the team engineered the mutation into mice, they slept less without anyobvious effect on health or memory.

　　NPSR1基因为大脑中一种参与觉醒和睡眠行为的蛋白质受体编码。当研究小组把这种突变基因植入老鼠体内时，它们的睡眠时间减少了，但对健康和记忆力没有明显影响。

　　Another variation in NPSR1 has previously been linked to people requiring 20 minutes lesssleep than average, based on studies of tens of thousands of people.

　　此前针对上万人的研究发现，NPSR1基因的另一种变异与所需睡眠时间比平均少20分钟的人有关。

　　On average, people need 8 hours sleep a night. In most people, sleeping less than 6 hours anight results in a marked decline in cognitive abilities within days. Over long periods, sleepdeprivation can contribute to many disorders, including obesity, heart disease, high bloodpressure, diabetes and depression.

　　平均而言，人们每晚需要8小时的睡眠。对大多数人来说，每晚睡眠不足6小时会导致认知能力在几天内显著下降。长时间缺乏睡眠会导致许多疾病，包括肥胖、心脏病、高血压、糖尿病和抑郁症。

　　As far as Fu's team has been able to tell, however, people who sleep less because they haveone of these gene variants are healthy and don't appear to suffer any ill effects. However, to beabsolutely sure would require long-term studies involving large numbers of people, which isn'tfeasible.

　　然而，就傅嫈惠的研究小组所知，那些因为拥有这些基因变异而睡眠较少的人是健康的，而且似乎没有任何不良影响。但要想完全确定，就需要进行涉及大量人群的长期研究，这是不可行的。

　　"Right now, we cannot say for sure," says Fu.

　　傅嫈惠说：“现在，我们还不太肯定。”

　　In theory, if these gene variants provided a big advantage, evolution should have madethem common – yet they appear to be rare. It might be, say, that sleeping less only becamean advantage after the development of lights. But other advantageous gene variants thatappeared only recently in human history, such as those allowing adults to digest milk, becamewidespread very rapidly.

　　从理论上讲，如果这些基因变异提供了一个巨大的优势，进化应该会使它们变得普遍，但目前看来还很罕见。这可能是因为，少睡觉只是在灯光发明之后才成为一种优势。但是其他有利的基因变异，比如那些允许成年人消化牛奶的基因变异，在人类历史上只是最近才出现的，却迅速传播开来。

　　It might be possible to develop drugs that mimic the effects of these mutations. However, asNPSR1 is also involved in processes such as stress, anxiety and fear, there is a risk of nastyside effects.

　　研究人员能够开发模仿这些基因突变的药物，但由于NPSR1基因也与压力、焦虑和恐惧等情绪有关，因此有可能导致严重的副作用。

　　Expect more reports soon. Fu say her team has already discovered more sleep-shorteningmutations.

　　我们期待不久之后能有更多的报道。傅嫈惠说，她的团队已经发现了更多与睡眠时间短有关的基因突变。