白天時間不夠用，晚上睡眠不好?但現實生活中，確實有些人每天睡眠時間很短，卻精神飽滿。為什麼有些人每天只需要睡4、5個小時?這其實是由基因決定的。
A genetic mutation that allows people to feel fully rested with fewer than six hours sleep a night has been identified by studying a family who get by on less than average. It is the second such finding in recent months.
科學家通過對一個家庭的研究，發現了一種可以使人在每晚睡眠不足6小時的情況下得到充分休息的基因突變。這個家庭的成員每日睡眠時長低於平均水平。這是近幾個月來第二個針對這一問題的同類發現。
Ying-Hui Fu at the University of California, San Francisco, and her colleagues have been seeking out and studying families in which some people seem to need less sleep than normal. They have been looking for the gene variants that might be responsible, and genetically engineering these variants into mice to confirm their effect.
加州大學舊金山分校的傅嫈惠和她的同事們一直在尋找和研究那些所需睡眠少於平均水平的家庭。他們一直在尋找可能起作用的基因變異，並通過基因技術將這些變異的基因植入老鼠體內以證實其作用。
Her team has found several mutations make people need less sleep. In August, Fu’s team reported that a mutation in a gene called ADRB1 allows 12 members of a family to sleep as little as 4.5 hours per night without feeling tired. This gene codes for a receptor protein common in a brain region called the dorsal pons, known to regulate sleep.
她的團隊已經發現了幾種基因突變會使人們需要更少的睡眠。今年8月，傅嫈惠的研究小組報告稱，ADRB1基因突變使一個家庭的12名成員每晚只睡4.5小時而不會感到疲勞。這種基因為一種受體蛋白編碼，這種蛋白在大腦中的腦橋背側區域很常見，這一區域負責調節睡眠。
mutation [mjuːˈteɪʃn]：n. 突變;變化
Now the team has found a mutation in a gene called NPSR1 in another family in which some people report feeling fully rested after much less sleep than average. Of the two members of this family whose sleep habits they studied, one averaged 5.5 hours a night and the other just 4.3 hours.
現在，研究小組在另一個家庭中發現了NPSR1基因突變，一些家庭成員報告說，他們在睡眠時間遠遠少於平均水平的情況下，仍然感到精力充沛。他們研究了其中兩名家庭成員的睡眠習慣，一人平均每晚睡5.5小時，另一人僅睡4.3小時。
NPSR1 codes for a protein receptor in the brain known to be involved in arousal and sleep behaviour. When the team engineered the mutation into mice, they slept less without any obvious effect on health or memory.
NPSR1基因為大腦中一種參與覺醒和睡眠行為的蛋白質受體編碼。當研究小組把這種突變基因植入老鼠體內時，它們的睡眠時間減少了，但對健康和記憶力沒有明顯影響。
Another variation in NPSR1 has previously been linked to people requiring 20 minutes less sleep than average, based on studies of tens of thousands of people.
此前針對上萬人的研究發現，NPSR1基因的另一種變異與所需睡眠時間比平均少20分鐘的人有關。
On average, people need 8 hours sleep a night. In most people, sleeping less than 6 hours a night results in a marked decline in cognitive abilities within days. Over long periods, sleep deprivation can contribute to many disorders, including obesity, heart disease, high blood pressure, diabetes and depression.
平均而言，人們每晚需要8小時的睡眠。對大多數人來說，每晚睡眠不足6小時會導致認知能力在幾天內顯著下降。長時間缺乏睡眠會導致許多疾病，包括肥胖、心臟病、高血壓、糖尿病和抑鬱症。
sleep deprivation：睡眠不足
As far as Fu’s team has been able to tell, however, people who sleep less because they have one of these gene variants are healthy and don’t appear to suffer any ill effects. However, to be absolutely sure would require long-term studies involving large numbers of people, which isn’t feasible.
然而，就傅嫈惠的研究小組所知，那些因為擁有這些基因變異而睡眠較少的人是健康的，而且似乎沒有任何不良影響。但要想完全確定，就需要進行涉及大量人群的長期研究，這是不可行的。
「Right now, we cannot say for sure,」 says Fu.
傅嫈惠說：「現在，我們還不太肯定。」
In theory, if these gene variants provided a big advantage, evolution should have made them common – yet they appear to be rare. It might be, say, that sleeping less only became an advantage after the development of lights. But other advantageous gene variants that appeared only recently in human history, such as those allowing adults to digest milk, became widespread very rapidly.
從理論上講，如果這些基因變異提供了一個巨大的優勢，進化應該會使它們變得普遍，但目前看來還很罕見。這可能是因為，少睡覺只是在燈光發明之後才成為一種優勢。但是其他有利的基因變異，比如那些允許成年人消化牛奶的基因變異，在人類歷史上只是最近才出現的，卻迅速傳播開來。
It might be possible to develop drugs that mimic the effects of these mutations. However, as NPSR1 is also involved in processes such as stress, anxiety and fear, there is a risk of nasty side effects.
研究人員能夠開發模仿這些基因突變的藥物，但由於NPSR1基因也與壓力、焦慮和恐懼等情緒有關，因此有可能導致嚴重的副作用。
Expect more reports soon. Fu say her team has already discovered more sleep-shortening mutations.
我們期待不久之後能有更多的報導。傅嫈惠說，她的團隊已經發現了更多與睡眠時間短有關的基因突變。