睡眠的藝術

By+James+Hamblin

你是否也有睡“假覺”的經歷？整夜輾轉反側，身體極度疲勞，腦中卻上演著金戈鐵馬；好不容易睡著了，一早醒來，還是精神萎靡，總有一種說不出的疲憊感。究竟是什么在影響著你的睡眠質量？人究竟需要多少睡眠？我們能夠訓練自己睡得更少嗎？怎樣才能睡得更好？這是一篇由醫生和專家提供的科學睡眠指南。

During residency， I worked hospital shifts that could last 36 hours，1 without sleep， often without breaks of more than a few minutes. Even writing this now， it sounds to me like Im bragging or laying claim to some fortitude of character.2 I cant think of another type of selfinjury that might be similarly lauded， except maybe binge drinking.3 Technically4 the shifts were 30 hours， but we stayed longer because people kept getting sick. Being a doctor is supposed to be about putting other peoples needs before your own. Our job was to power through5.

No matter what happened to my body， I never felt like it was dangerous for me to keep working. I knew I was irritable and sometimes terse，6 and I didnt smell the best， but I didnt think anything I did was unsafe. Sleep experts often liken sleepdeprived people to drunk drivers： They dont get behind the wheel thinking theyre probably going to kill someone.7 But as with drunkenness， one of the first things we lose in sleep deprivation is self-awareness.

Its this way of thinking—that you can power through， that sleep is the easiest corner to cut—that makes sleep disturbance among the most common sources of health problems in many countries.8 Insufficient sleep causes many chronic and acute medical conditions that have an enormous impact on quality of life，9 not to mention the economy. While no one knows why we sleep， it is a universal biological imperative10； no animal with a brain can survive without it. Dolphins are said to sleep with only half their brain at a time， keeping partially alert for predators.11 Many of us spend much of our lives in a similar state.

How much sleep do I actually need？

The American Academy of Sleep Medicine and the Sleep Research Society convened a body of scientists from around the world to answer this question through a review of known researches.12 They looked at the effects of sleep on cardiovascular disease， cancer， obesity， cognitive failure， and human performance， vetting each paper based on its scientific strength.13

The consensus14： Most adults function best after seven to nine hours of sleep a night. Going to sleep and waking up at consistent15 times each day is valuable too. When we get fewer than seven hours， were impaired16 （to degrees that vary from person to person）. When sleep persistently falls below six hours per 24， we are at an increased risk of health problems.

Can I train myself to need less sleep？

As an experiment for his high-school science fair in 1964， a 17-year-old San Diego boy named Randy Gardner stayed awake for 264 hours. That is 11 days. The project attracted the attention of the Stanford sleep researcher William Dement， among others. Dement and other researchers took turns watching and assessing the young mans consciousness. By all accounts， he took no stimulant medications.17 Nor did he seem to suffer any permanent deficits.18

How many people could do anything close to that without dying？ David Dinges， the chief of the division of sleep and chronobiology19 at the University of Pennsylvania， said that“when animals are sleep-deprived constantly， they will suffer serious biological consequences. Death is one of those consequences.”

Around the time of Gardners historic science project， the U.S. military got interested in sleep-deprivation research： Could soldiers be trained to function in sustained warfare20 with very little sleep？ The original studies seemed to say yes. But when the military put soldiers in a lab to make certain they stayed awake， performance suffered. Cumulative deficits accrued with each night of suboptimal sleep.21 The less sleep the soldiers got， the more deficits they suffered the next day. But as with my own residency experience， they couldnt tell that they had a deficit.

“They would insist that they were fine，”said Dinges， “but werent performing well at all.”

I drink coffee instead of sleeping， so Im fine.

Caffeine is the most consumed stimulant in the world. The chemical induces reactions throughout the body that normally occur in intense situations.22 When we sense danger， for example， our body releases adrenaline23 into our blood.

Adrenaline is the hormone thats meant to be released when we are under stress and need to muster energy to， say， outrun a bear.24 Caffeine increases adrenaline levels in the blood. It has been shown to improve athletic performance in the short term， from how high a person can jump to how fast a person can swim.

Thanks to caffeine， many of us stimulate fight-or-flight response not just occasionally， under dire circumstances，25 but daily， in our offices. Eighty-five percent of U.S. adults consume some form of caffeine most days， with an average daily dose of 300 milligrams （roughly 790ml of coffee）. Strategic use of small amounts of caffeine can be cognitively advantageous， but at such a high dose， caffeine is likely to throw off our sleep and energy cycles in the long term， altering the bodys internal clock.26 At that point， many people go in search of products to help them sleep.

I cant sleep. Is my phone really keeping me up？

The United Nations declared 2015 to be the International Year of Light and Light-Based Technologies27. It was trying to reckon with28 the invasion of all this new light into our lives.

Of all the things to have health concerns about， light？ Well， yes. When light enters your eye， it hits your retina， which relays signals directly to the core of your brain， the hypothalamus.29 The size of an almond， the hypothalamus has more importance per volume than any other part of your body. This almond is the interface between the electricity of the nervous system and the hormones of the endocrine system.30 It takes sensory31 information and directs the bodys responses， so that the body can stay alive.

Among other roles in maintaining bodily homeostasis32—appetite， thirst， heart rate， etc.—the hypothalamus controls sleep cycles. It doesnt bother consulting with the cerebral cortex33， so you are not conscious of this. But when your retinas start taking in less light， your hypothalamus assumes its time to sleep. So it wakes up its neighbor the pineal gland and says，“Hey， make some melatonin and shoot it into the blood.”34 And the pineal gland says， “Yes， okay，” and it makes the hormone melatonin and shoots it into the blood， and you become sleepy. In the morning， the hypothalamus senses light and tells the pineal gland to stop its work， which it does. Test your blood for melatonin during the daytime， and you will find almost none.

All of this is why were told to minimize screen time before bed. Phones and tablets emit light thats skewed heavily toward the blue end of the visible spectrum， and some research suggests that these frequencies are especially influential in human sleep cycles.35 Using a “night mode，” available on some phones， is supposed to minimize that effect. Thats probably worth doing—so long as you dont end up canceling out any benefit by spending more time looking at the lit screen.

1. residency： （實習醫師的）高級專科住院實習期，在美國通常為三至七年，工作時間長、強度大；shift： 輪班工作時間。

2. brag： 吹牛，自夸；lay claim to： 自稱有……；fortitude： 剛毅，堅韌。

3. laud： 贊美，頌揚；binge drinking： 酗酒，豪飲，binge指無節制的狂熱行動，binge drinking指為喝酒而喝酒的毫無節制的縱酒行為。同義詞excessive drinking。

4. technically： 嚴格意義上來說。

5. power through： 全力前進，飛速行進。

6. irritable： 易怒的，煩躁的；terse：簡短生硬的，唐突草率的。

7. liken： 把……比作；sleep-deprived：睡眠不足的，缺乏睡眠的，下句中deprivation意為“缺乏”；get behind the wheel： 握方向盤，即開車，駕駛。

8. 正是由于這樣的想法——你可以鉚足勁強撐過去，睡眠最容易被“偷工減料”——使得睡眠紊亂成為許多國家健康問題最常見的根源之一。cut corners： 草草行事，偷工減料。

9. insufficient： 不足的，不充分的；chronic：（疾病）慢性的；acute：（疾病）急性的。

10. imperative： 必要的事，緊急的事。

11. alert： 警覺的，警惕的；predator： 捕食者。

12. American Academy of Sleep Medicine： 美國睡眠醫學學會，成立于1975年；Sleep Research Society：（美國）睡眠研究協會，成立于1961年，是一家促進睡眠研究及有關睡眠紊亂癥醫學研究的專業機構，convene： 召集（會議），集合；review： 回顧，審查。

13. cardiovascular disease： 心血管疾病；obesity： 肥胖癥，過度肥胖；cognitive： 認知的；vet： v. 審查。

14. consensus： 共識，一致意見。

15. consistent： 始終如一的。

16. impaired： 受損害的，被削弱的。

17. by all accounts： 據大家所說；stimulant medication： 使人興奮的藥物，下文中的stimulant為名詞，興奮劑。

18. permanent： 永久的，固定的；deficit： 缺陷，障礙。

19. chronobiology： 時間生物學，又稱生物鐘學，主要研究生物體內與時間相關的周期性現象。

20. warfare： 戰爭，作戰。

21. 每天晚上的睡眠不足使他們暴露出越來越多的缺陷。cumulative：累積的；accrue： （通過增長、積累而）產生，形成；suboptimal：未達到最佳標準的，不是最令人滿意的。

22. induce： 引起，招致；intense： 緊張的，強烈的。

23. adrenaline： 腎上腺素，腎上腺分泌的一種激素及神經傳導物質，能使心跳加快，讓人在興奮、恐懼、緊張或憤怒時精力猛增。

24. hormone： 荷爾蒙，激素；muster： 聚集（力量、精力等）；outrun：（為避免被抓獲而）跑得比……快，從……逃脫。

25. stimulate： 刺激；fight-or-flight response：戰斗或逃跑反應，心理學名詞，為1929年美國生理學家懷特·坎農所創造，指機體經一系列神經和腺體反應會被引發應激狀態，使軀體做好防御、掙扎或逃跑的準備；dire：嚴重的，可怕的。

26. 戰略性地攝入少量咖啡因會對我們的認知能力有益，但是攝入量如此之大，從長遠來看，咖啡因很有可能會擾亂我們的睡眠和能量周期，改變人體內部的生物鐘。throw off： 擺脫習慣。

27. International Year of Light and LightBased Technologies： 國際光之年，聯合國教科文組織將2015年定為“國際光之年”，旨在提升大眾對光學科學、其應用，以及其對人類重要性的認識。

28. reckon with： 認真處理，小心對付。

29. retina： 視網膜；relay： 傳遞；hypothalamus： 下丘腦，管理著人體的許多功能，包括睡眠、體溫、口渴和饑餓。

30. 這個杏核大小的大腦部件是神經系統電信號和內分泌系統荷爾蒙之間的交匯界面。endocrine： 內分泌的。

31. sensory： 知覺的，感官上的。

32. homeostasis： 體內平衡。

33. cerebral cortex： 大腦皮層。

34. pineal gland： 松果體，這個內分泌小腺體介于兩個大腦半球之間，被裹在兩個圓形的丘腦的接合處，是人體最小的器官，負責制造褪黑素；melatonin： 褪黑素，一種荷爾蒙，因其可以使青蛙皮膚顏色變淺而得名，是一種調節生物鐘的激素；shoot： 注射。

35. emit： 發出；skew： 向……傾斜；visible spectrum： 可見光譜，是電磁波譜中肉眼可見的一部分，藍光是其中能量最強也最具危害性的光線，會對眼睛和視力造成很大損害。