睡眠的艺术

By+James+Hamblin

你是否也有睡“假覺”的经历？整夜辗转反侧，身体极度疲劳，脑中却上演着金戈铁马；好不容易睡着了，一早醒来，还是精神萎靡，总有一种说不出的疲惫感。究竟是什么在影响着你的睡眠质量？人究竟需要多少睡眠？我们能够训练自己睡得更少吗？怎样才能睡得更好？这是一篇由医生和专家提供的科学睡眠指南。

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： （實习医师的）高级专科住院实习期，在美国通常为三至七年，工作时间长、强度大；shift： 轮班工作时间。

2. brag： 吹牛，自夸；lay claim to： 自称有……；fortitude： 刚毅，坚韧。

3. laud： 赞美，颂扬；binge drinking： 酗酒，豪饮，binge指无节制的狂热行动，binge drinking指为喝酒而喝酒的毫无节制的纵酒行为。同义词excessive drinking。

4. technically： 严格意义上来说。

5. power through： 全力前进，飞速行进。

6. irritable： 易怒的，烦躁的；terse：简短生硬的，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意为“缺乏”；get behind the wheel： 握方向盘，即开车，驾驶。

8. 正是由于这样的想法——你可以铆足劲强撑过去，睡眠最容易被“偷工减料”——使得睡眠紊乱成为许多国家健康问题最常见的根源之一。cut corners： 草草行事，偷工减料。

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，紧急的事。

11. alert： 警觉的，警惕的；predator： 捕食者。

12. American Academy of Sleep Medicine： 美国睡眠医学学会，成立于1975年；Sleep Research Society：（美国）睡眠研究协会，成立于1961年，是一家促进睡眠研究及有关睡眠紊乱症医学研究的专业机构，convene： 召集（会议），集合；review： 回顾，审查。

13. cardiovascular disease： 心血管疾病；obesity： 肥胖症，过度肥胖；cognitive： 认知的；vet： v. 审查。

14. consensus： 共识，一致意见。

15. consistent： 始终如一的。

16. impaired： 受损害的，被削弱的。

17. by all accounts： 据大家所说；stimulant medication： 使人兴奋的药物，下文中的stimulant为名词，兴奋剂。

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

19. chronobiology： 时间生物学，又称生物钟学，主要研究生物体内与时间相关的周期性现象。

20. warfare： 战争，作战。

21. 每天晚上的睡眠不足使他们暴露出越来越多的缺陷。cumulative：累积的；accrue： （通过增长、积累而）产生，形成；suboptimal：未达到最佳标准的，不是最令人满意的。

22. induce： 引起，招致；intense： 紧张的，强烈的。

23. adrenaline： 肾上腺素，肾上腺分泌的一种激素及神经传导物质，能使心跳加快，让人在兴奋、恐惧、紧张或愤怒时精力猛增。

24. hormone： 荷尔蒙，激素；muster： 聚集（力量、精力等）；outrun：（为避免被抓获而）跑得比……快，从……逃脱。

25. stimulate： 刺激；fight-or-flight response：战斗或逃跑反应，心理学名词，为1929年美国生理学家怀特·坎农所创造，指机体经一系列神经和腺体反应会被引发应激状态，使躯体做好防御、挣扎或逃跑的准备；dire：严重的，可怕的。

26. 战略性地摄入少量咖啡因会对我们的认知能力有益，但是摄入量如此之大，從长远来看，咖啡因很有可能会扰乱我们的睡眠和能量周期，改变人体内部的生物钟。throw off： 摆脱习惯。

27. International Year of Light and LightBased Technologies： 国际光之年，联合国教科文组织将2015年定为“国际光之年”，旨在提升大众对光学科学、其应用，以及其对人类重要性的认识。

28. reckon with： 认真处理，小心对付。

29. retina： 视网膜；relay： 传递；hypothalamus： 下丘脑，管理着人体的许多功能，包括睡眠、体温、口渴和饥饿。

30. 这个杏核大小的大脑部件是神经系统电信号和内分泌系统荷尔蒙之间的交汇界面。endocrine： 内分泌的。

31. sensory： 知觉的，感官上的。

32. homeostasis： 体内平衡。

33. cerebral cortex： 大脑皮层。

34. pineal gland： 松果体，这个内分泌小腺体介于两个大脑半球之间，被裹在两个圆形的丘脑的接合处，是人体最小的器官，负责制造褪黑素；melatonin： 褪黑素，一种荷尔蒙，因其可以使青蛙皮肤颜色变浅而得名，是一种调节生物钟的激素；shoot： 注射。

35. emit： 发出；skew： 向……倾斜；visible spectrum： 可见光谱，是电磁波谱中肉眼可见的一部分，蓝光是其中能量最强也最具危害性的光线，会对眼睛和视力造成很大损害。