Sleeping in on Saturday after a few weeks of too little shuteye may feel refreshing, but it can give a false sense of security.

    New research shows chronic sleep loss cannot be cured that easily. Scientists teased apart the effects of short- and long-term sleep loss and found that the chronically sleep-deprived may function normally soon after waking up,but experience steadily slower reaction times as the day wears on, even if they had tried to catch up the previous night.

    It is work with important safety implications in an increasingly busy society, not just for shift-workers but for the roughly one in six Americans who regularly get six hours or less of sleep a night.

    "We know that staying awake 24 hours in a row impairs performance to alevel comparable to a blood-alcohol content beyond the legal limit todrive," said lead researcher Dr. Daniel Cohen of Boston's Brigham andWomen's Hospital.

    But when the chronically sleep-deprived pull an all-nighter, "the deterioration is increased tenfold," Cohen said.

    The National Institutes of Health says adults need seven hours to ninehours of sleep for good health. Regularly getting too little increasesthe risk of health problems, including memory impairment and a weakenedimmune system. More immediately, too little sleep affects reactiontimes; sleepiness is to blame for car crashes and other accidents.

    The new work shows how two different sleep drives impact the brain, oneduring the normal waking hours and the other over days and weeks ofsleep loss.

    It has critically important ramifications for anyone who works "crazy hours" and thinks they are performing fine with a few hours of weeknight

    sleep, said Shelby Freedman Harris, behavioral sleep-medicine directorat New York's Montefiore Medical Center, who was not involved with thenew research.

    "Don't think you can just bank up your sleep on the weekend, because it doesn't work that way," Harris warned.

    在一連幾個(gè)星期睡眠不足的情況下，到了周六睡個(gè)懶覺可能會(huì)讓你感到神清氣爽，但這會(huì)給你一種錯(cuò)誤的安全感。

    最新研究表明，長(zhǎng)期缺覺沒那么容易補(bǔ)回來�？茖W(xué)家分別對(duì)短期和長(zhǎng)期缺覺的影響進(jìn)行了研究，發(fā)現(xiàn)長(zhǎng)期缺覺的人在醒來后可能可以很快進(jìn)入正常狀態(tài)，但在當(dāng)天之后，反應(yīng)速度會(huì)逐漸變慢，即便他們?cè)噲D補(bǔ)回前一夜缺的睡眠。

    在如今日益繁忙的社會(huì)，這項(xiàng)研究具有重要的安全警示意義，不僅對(duì)于那些需要倒班的人來說如此，對(duì)于那些每晚睡眠不足六小時(shí)的六分之一美國(guó)人來說也一樣。

    該研究負(fù)責(zé)人、波士頓布萊根女子醫(yī)院的丹尼爾？科恩博士說："我們知道，一連24小時(shí)不睡覺會(huì)影響你做各種事情的表現(xiàn)，這種影響相當(dāng)于在飲酒過量時(shí)駕車。"

    但如果長(zhǎng)期缺覺的人徹夜不眠，"這種影響會(huì)增加十倍".

    美國(guó)國(guó)立衛(wèi)生研究院說，成年人每天需要七至九個(gè)小時(shí)的睡眠才可保持身體健康。長(zhǎng)期缺覺會(huì)增加患病風(fēng)險(xiǎn)，包括對(duì)記憶力的損害和免疫能力下降。更直接的影響是，睡眠不足會(huì)影響反應(yīng)速度，開車時(shí)打瞌睡是導(dǎo)致撞車等事故的主要原因。

    這項(xiàng)新的研究揭示了兩種不同的睡眠驅(qū)力是如何對(duì)大腦產(chǎn)生影響的，一種是在正常清醒的狀態(tài)下，另一種是在連續(xù)幾天或幾個(gè)星期缺覺的情況下。

    紐約蒙特費(fèi)爾醫(yī)療中心的行為睡眠醫(yī)學(xué)主任謝爾比？弗里德曼？哈里斯說，這項(xiàng)研究對(duì)于那些玩命工作，卻還認(rèn)為每天睡幾個(gè)小時(shí)也能應(yīng)付的人來說具有極其重要的警示作用。哈里斯沒有參與這項(xiàng)新研究。

    哈里斯警告說："不要以為周末睡個(gè)懶覺就能把睡眠補(bǔ)回來，因?yàn)楦�本不是那么回事�?quot;