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As anyone who has unwittingly drifted off at their desk will know-tiredness can really creep up on you when you least need it. But a new study is offering some good news： it claims to prove that we can bank sleep-and store it up in advance of a tiring event.

曾不知不覺在書桌旁打瞌睡的人都會知道，疲倦真的會在你最不需要它的時候悄悄地上身。但是一項新研究帶來些許好消息：它宣稱已證實我們可以儲存睡眠—在疲倦時刻來臨前先儲存睡眠。

Researchers in the US invited a group of volunteers to adjust their sleep patterns so the effect could be monitored.

美國的研究人員邀請一組志願者調整睡眠模式，好監控效果。

For a week, one half of the group were allowed extra sleep, while the others were told to keep their sleeping patterns the same. Then, the following week, they were all sleep-deprived.

一半的人在一周內可以多睡一點，另一半的人則維持原來的睡眠模式。隔週，全部的人都被剝奪睡眠。

"After this week of either extended or habitual sleep per night, all the volunteers came to the lab and they were given three hours of sleep, per night, for a week," explained Tracy Rupp from the Walter Reed Army Institute of Research.

華特里德陸軍研究院的路普解釋：「經過這個不管是多睡或是延續睡眠習慣的一周，所有志願者來到實驗室，度過每晚睡三小時的一周。」

They were then given tasks of varying complication, and tests showed that those who had banked the sleep were "more resilient during the sleep restriction".

接著分派志願者來做不同複雜度的工作，測試顯示，儲存睡眠的人，「在睡眠限制時較能迅速恢復精力。」

"They showed less performance deterioration with regards to reaction time and alertness than the group that had been given the habitual prior sleep," said Ms Rupp.

路普說：「就反應時間與警覺性而言，和延續睡眠習慣組的人相比，他們的表現都比較未受影響。」

新聞辭典

bank：動詞，儲存。

drift off：片語，漸漸睡著。例句：I couldn’t help drifting off in the middle of that lecture-it was so boring!（那堂課實在太無聊，我忍不住就睡著了！）

creep：動詞，緩慢前進，匍匐前進。例句：Over the last year, the rate of inflation has crept up to almost 7%.（過去一年，通膨率緩緩上升到近7%。）