許多人的睡眠時間比他們該睡的要少。而后果就是他們的大腦在為此付出代價。

Nothing feels worse than hearing your alarm clock ring in the morning when your body is screaming for a few extra hours of rest. Given the opportunity, who wouldn’t get more sleep? If I had a choice between a year of unlimited Easter candy and a year of unlimited sleep, I’d say “Bye-bye Cadbury” and “Hello, bed!”

Many people don’t get as much sleep as they should. Since the invention of the light bulb, people sleep about 500 hours per year less than they used to. Whether we’re kept awake by our partner’s snoring or we stay up too late watching TV, we wake up tired, groggy, and cranky. No wonder the coffee industry does so well. Unfortunately, sleep deprivation has some side effects and they can’t all be remedied with a little extra caffeine.

This Is Your Brain on Sleep

While the mechanism of sleep isn’t fully understood yet, doctors and scientists do know that it’s one of our body’s most important processes. Studies show that sleep is important for cellular renewal, helping to replace muscle tissue and dead cells throughout the body. Studies have also shown that sleep is a key time for the brain to process and archive information, including memories. Deep, restorative REM sleep, the kind associated with dreaming, seems to stimulate regions of the brain used in learning.

Every night without adequate rest is like adding to a sleep debt—eventually it will have to be repaid. Even after one sleepless night, we can feel the first effects of sleep deprivation—irritability, memory loss, and drowsiness. Continued sleep deprivation can result in trouble concentrating, blurry vision, impaired judgment, and even more severe mental effects. After just a few days without any sleep, people can begin to experience hallucinations, mania, and nausea. Luckily, if you repay your sleep debt right away, those effects vanish immediately.

Short-Term Side Effects

Sleep deprivation doesn’t just cause mental deficits; our physical abilities are diminished too. Studies have demonstrated that not sleeping can reduce glucose metabolism by as much as 40 percent. We use stored glucose for energy and sleep deprivation can interfere with how the body stores and processes it. Sleep-deprived athletes also experience high levels of cortisol, a stress hormone, as well as lower levels of human growth hormone, which is important for muscle repair. The immune system is also thought to be maintained while asleep; people who don’t get enough sleep tend to be more susceptible to infections and have slower healing times.

Sleep deprivation also has an effect on how the brain stores information. A study at the University of Pennsylvania showed that mice who were taught a task and allowed to sleep afterward remembered what they had learned better than mice that didn’t sleep. Among school-aged children, those who get even one less hour of sleep than their peers have shown to perform more poorly on tests of memory and attention.

Some of the effects of short-term sleep deprivation can be very similar to the effects of being drunk. In 2000, researchers in New Zealand and Australia found that people who drive after being awake for seventeen to nineteen hours performed worse on tests than people with a blood alcohol level of 0.05 percent, almost the legal limit for drunk driving. In fact, the U.S. Department of Transportation reports that as many as 100,000 sleep-related auto accidents occur every year.

One study found that sleep-deprived medical interns working on the night shift were twice as likely to misinterpret patients’ test results. There is even evidence that sleep deprivation may have played a part in some major disasters, including the Exxon Valdez oil spill.

Long-Term Consequences

It’s easy to erase the short-term effects of sleep deprivation—get more sleep. However, when people don’t sleep well for weeks, months, or even years, it can have cumulative effects on their health. Sleep has shown to be important in regulating blood sugar levels and people who don’t sleep can become increasingly resistant to insulin. Long-term insulin resistance puts extra burdens on the pancreas to produce more, and eventually can result in type 2 diabetes.

Recent studies have also linked chronic sleep deprivation to obesity. Sleep has an important effect on the hormones ghrelin and leptin, which control hunger and appetite. When we don’t sleep, these hormones can go out of balance, causing us to eat more than we need. Heart disease, high blood pressure, and depression are other diseases that can result from long-term sleep deprivation.

Get Forty Winks … At Least

It’s common to feel a bit tired in the morning, but how do you know if you’re truly sleep-deprived? Sleep experts say that if you feel groggy or tired during the day, feel the urge to nap, or if you fall asleep within five minutes of lying down, you could possibly be sleep-deprived. Another symptom of severe sleep debt is the occurrence of “microsleeps,” short bursts of sleep that can happen without a person even realizing it.

Although most people think they need to sleep for eight hours a night, the amount actually varies from person to person; some are fine with five, others would do better with ten. If you feel like you need more sleep, simple lifestyle changes can help you get more. Missing a few hours of sleep on occasion isn’t the end of the world, because it’s easy to make up the sleep with no lasting side effects. Many people are psychologically adjusted to constantly feeling tired, and in the short-term, their bodies may be able to adjust too. But the long-term consequences of sleep deprivation should be enough to convince anyone to hit the sack.

沒有比早晨你的起床鬧鐘鈴響了而你的身體卻還在渴求再多幾個鐘頭休息更讓人感覺糟糕的了。只要有機會，誰不會想再多睡會兒呢？如果能讓我在一年內(nèi)無限制地享用復(fù)活節(jié)糖果和一年內(nèi)能享受無限制的睡眠之間做選擇的話，我會說“再見，吉百利糖果”和“你好，床榻！”的。

許多人沒有得到他們應(yīng)該得到的足夠的睡眠。自從燈泡發(fā)明之后，人們比沒有燈泡的時代平均一年少睡500個小時的覺。不管原因是我們被伴侶的鼾聲折磨得睡不著還是因為看電視看得太晚，我們醒來后感覺疲憊不堪、昏昏沉沉、脾氣暴躁。無怪乎咖啡行業(yè)生意如此興隆。不幸的是，睡眠的被剝奪有一些副作用不是單靠一點額外的咖啡因就能矯治的。

這是你的大腦在休息

雖然迄今為止關(guān)于睡眠的機制還沒有完全被了解，醫(yī)生們和科學(xué)家們已經(jīng)確知它是我們身體最重要的生理過程之一。研究表明睡眠對細(xì)胞更新至關(guān)重要，幫助在全身范圍內(nèi)替換老的肌肉纖維和死細(xì)胞。研究也表明睡眠時間是大腦處理和存儲信息包括記憶的重要時段。深層的,恢復(fù)性的眼球快速運動（REM）睡眠,也就是與做夢相關(guān)的那種睡眠，似乎能刺激大腦中用于學(xué)習(xí)的那些部分。

每個晚上沒有足夠的休息就像讓睡眠欠上了債--而債最終是得還的。哪怕只是一夜不眠，我們都能感到睡眠被剝奪的最初的癥狀—易怒、記憶喪失和昏昏欲睡。持續(xù)的睡眠剝奪能導(dǎo)致注意力難以集中、視野模糊、缺乏判斷力，甚至是更嚴(yán)重的腦部癥狀。只要一連幾天不睡覺，人會開始出現(xiàn)幻覺、躁狂癥和惡心。幸運的是，如果你馬上償還睡眠欠賬，這些癥狀馬上就會消失。

短期副作用

睡眠剝奪不僅僅導(dǎo)致腦部功能缺失，它也會減弱我們的身體行動能力。研究顯示不睡覺會降低葡萄糖代謝達(dá)40%之多。我們的身體儲存葡萄糖為備用能源而睡眠剝奪干擾了身體儲存和處理葡萄糖的過程。被剝奪睡眠的運動員體內(nèi)會經(jīng)歷高水平的氫化可的松--這是一種造成緊張的荷爾蒙，也會出現(xiàn)低水平的人類生長荷爾蒙—該荷爾蒙對肌肉的修復(fù)很重要。人的免疫系統(tǒng)也被認(rèn)為是在睡眠時進(jìn)行維護(hù)的；睡眠不足的人傾向于更易感染疾病而且治愈需更長時間。

睡眠剝奪對大腦存儲信息也有影響。一項在賓夕法尼亞大學(xué)進(jìn)行的研究顯示那些被教會一項任務(wù)并在事后被允許休息的老鼠比那些事后不睡的老鼠對所學(xué)任務(wù)要記得牢。在學(xué)齡兒童中，那些僅僅比他們的同儕少睡一小時的兒童在記憶力和注意力測試中表現(xiàn)得要更差。

短期睡眠剝奪的某些影響與醉酒的后果類似。2000年新西蘭和澳大利亞的研究者們對連續(xù)17到19小時不睡后的人的汽車駕駛測試結(jié)果表明他們比那些血液中酒精濃度達(dá)到0.05%的人表現(xiàn)更差，而后者血液中酒精水平幾乎就是醉酒駕駛的法律界限。事實上美國交通部報告每年都有多達(dá)10萬起與睡眠有關(guān)的汽車事故發(fā)生。

一項研究發(fā)現(xiàn)睡眠被剝奪的上晚班的醫(yī)療實習(xí)生他們誤判病人病情測試結(jié)果的幾率要多一倍。甚至有證據(jù)顯示對于某些重大災(zāi)難的發(fā)生睡眠剝奪也在其中扮演了一定的角色，比如埃克森瓦爾德茲號油輪原油泄漏事故。

長期后果

短期睡眠剝奪的副作用是比較容易消除的--補點兒覺就成。然而當(dāng)人們連著幾周，幾個月甚至經(jīng)年睡不好時，這對他們的健康起的副作用就是累積的。睡眠已被證實對規(guī)范血糖水平至關(guān)重要，而那些不睡覺的人會變得越來越對胰島素抗拒。長期的對胰島素抗拒會對胰腺造成額外的負(fù)擔(dān)以迫使它產(chǎn)生更多的胰島素，而這最終會導(dǎo)致形成II型糖尿病。

最近的研究也把慢性睡眠剝奪與肥胖癥聯(lián)系起來。睡眠對腦腸肽和瘦素這兩種荷爾蒙有重要影響，而該兩種荷爾蒙控制人的饑餓感和食欲。當(dāng)我們不睡覺時這些荷爾蒙將會失衡，導(dǎo)致我們吃得比需要的多。心臟病、高血壓和憂郁癥是其它一些長期的睡眠剝奪可以導(dǎo)致的疾病。

至少閉目養(yǎng)養(yǎng)神吧

早晨起來感到有點疲倦很正常，但是你怎么才能知道你是真的處于睡眠被剝奪的狀態(tài)呢？睡眠專家們說如果你整天都感覺昏昏沉沉或疲憊不堪，很想要打個盹兒，或者是你躺下來五分鐘內(nèi)就去見了周公，你很可能已經(jīng)處于睡眠剝奪的狀態(tài)了。另外一個嚴(yán)重睡眠欠賬的并發(fā)癥現(xiàn)象是“（多次）微睡（microsleeps）”那是多次的短促的睡眠狀態(tài)，它發(fā)生時甚至你都意識不到。

盡管大部分人覺得他們一晚上應(yīng)該睡八個小時，實際上該睡多久卻因人而異；有些人睡五個小時就成，而另一些人就得睡十個小時才夠。如果你覺得你得多睡點兒，簡單的生活方式的改變能幫你得到它。偶爾缺幾個小時覺沒什么大不了的，因為很容易事后及時補覺而不會有長期的副作用。許多人對連續(xù)感到疲勞在心理上已經(jīng)做了調(diào)適，而在短期內(nèi)他們的身體也能做出調(diào)適。但如果是長期的睡眠剝奪其所帶來的后果應(yīng)該足夠能說服任何人趕緊上床睡覺。