Dangers of a good night's sleep
The subject of sleeplessness is once more under public discussion. The hurry and excitement of modern life is held to be responsible for much of the insomnia of which we hear; and most of the articles and letters are full of good advice to live more quietly and of platitudes concerning the harmfulness of rush and worry. The pity of it is that so many people are unable to follow this good advice and are obliged to lead a life of anxiety and high tension.
Jim Horne, director of Loughborough University's Sleep Research Centre, cites this editorial to show that there is nothing new about the current wave of concern that western populations are building up an unhealthy "sleep debt".
More than 100 years later, articles in the scientific and popular media are again claiming that the demands of work and leisure leave a significant proportion of people chronically deprived of sleep, with damaging effects on productivity, health and safety.
Typical is a recent editorial in Nature, the leading scientific journal, attacking the "misperception" that, because successful people can get by with just a few hours sleep a night, sleep is a waste of time.
"The tendency to sleep less - perhaps 20 per cent less in industrialised countries than a century ago - has serious consequences for public safety," Nature said. Sleep deprivation causes a significant proportion of road and rail crashes and other accidents, such as the 1989 Exxon Valdez oil tanker.
According to the US National Institutes of Health, sleep deprivation and disorders cost the nation $15bn (￡8.6bn) in health care ex-penses and $50bn in lost productivity every year. Yet a growing number of leading sleep researchers are speaking out against what they see as commercially motivated misrepresentation of sleep debt as a relatively new phenomenon. Prof Horne is one. Another is Daniel Kripke, research professor at the University of California, San Diego. "I believe most of this PR campaign is being managed by people who make money from hypnotics [sleeping pills] manufacturing or from commercial sleep clinics," he says.
Last month, for example, Nytol, GlaxoSmithKline's sleeping tablet brand, published a poll and report with Future Laboratory, a UK consumer consultancy, which concluded: "Sleep debt is a growing trend and phenomenon as our determination to keep shaving time off our sleep cycle leaves us exhausted, unfocused and cranky." It said people should aim for "8 hours of pure sleep".
Large-scale population studies by Prof Kripke and others show that 7 to 7.5 hours sleep per night is associated with the lowest levels of mortality; death rates increase significantly as sleep rises above 8 hours. "Yet many sleep researchers seem to think that seven to seven-and-a-half hours is insufficient for healthy ad-ults, and we should be sleeping an extra hour or so," says Prof Horne, whose book Sleepfaring will be published next month.
"The belief that we need at least eight hours sleep a night is actually making insomnia worse, by making people worry unnecessarily that they are getting less sleep than that," Prof Kripke says. He believes too much sleep may be a more serious health issue than too little; a clinical study is under way at the University of South Carolina to see whether people who sleep more than eight-and-a-half hours a night would benefit from spending less time in bed.
Prof Horne says the belief that people are sleeping less than their ancestors is based on a misunderstanding of old surveys - particularly an oft-quoted 1913 Stanford University study that looked at sleep in schoolchildren.
"It is simply not true to say that we are more sleep deprived today," he insists. "In fact many of us probably sleep better because bedrooms are much better designed now than their draughty, noisy counterparts 100 years ago." (A study of Canadian Inuit before electric lighting showed that they slept an average of six hours a day during the Arctic summer and 14 hours during the winter.)
Douglas Bradley, director of the Centre for Sleep Medicine and Circadian Biology at the University of Toronto, suggests a compromise. "I think our society is sleep deprived compared to the relatively tranquil period of the 1950s and 60s, when we we didn't have a coffee shop on every street corner, though not compared to the 19th century," he says. "But I agree that there are vested interests [exaggerating] the extent of the sleep debt."
Much of the experimental evidence supporting the sleep deprivation argument comes from questionnaires and laboratory studies of sleepiness, which may give a misleading impression, Prof Horne says. That people will sleep more, given the opportunity, does not mean that they are sleep deprived.
However Stephen Emegbo, a sleep researcher at the University of Surrey, be-lieves that Profs Horne and Kripke are underestimating the impact of modern society on sleep.
"The light bulb has been a wonderful invention for every sphere of life, except sleep," he says. "People will try to finish a task by staying up till 4 or 5am, rather than getting a good night's sleep and finishing it the next day. Whether or not people sleep less than in the past, I believe there is more disruption and fragmentation of sleep and more sleep disorders today."
According to IMS Health, a pharmaceutical market consultancy, prescriptions for sleeping pills rose by 13 per cent in the US last year to 43m. Some sleep specialists welcome the increase, which they say reflects the fact that the pharmaceutical industry is offering superior products to treat insomnia.
Others are concerned that, although the new drugs have fewer side-effects than the previous generations of sleeping pills, their long-term use could be hazardous - and could mask more fundamental health problems that are causing insomnia.
"The problem comes when these hypnotics are used for much longer than the four- to eight-week period for which they are intended," says Dr Emegbo.
Night shifts are a serious cause of occupational insomnia. "Most people on night shifts are chronically sleep deprived," says Prof Bradley, "but some shift patterns are more tolerable than others." The pattern followed by staff at his own sleep lab in Toronto, where the research requires night shifts, is for people to work three consecutive 12-hour nights, followed by a three-day break and five consecutive day shifts.
For businesses that re-quire eight-hour night shifts, Prof Bradley says the best pattern is a rotation of mornings (6am-2pm), then afternoons (2pm-10pm) and nights (10pm-6pm): "It is important to rotate in that order, because our body clocks have a natural tendency to extend the day."
Sleeplessness, it is safe to predict, will remain "under public discussion" for many years to come.
“晚安”之后的威胁
失眠再一次成了公众讨论的话题。现代生活的匆忙与刺激被认为造成了我们所耳闻的大多失眠现象；大多文章与信件里都满是要生活得更闲静的好建议，也满是匆忙与担忧造成危害的陈词滥调。遗憾的是，太多人无法按照建议去做，不得已过着焦虑而高度紧张的生活。
《英国医学期刊》(British Medical Journal)，1894年。
拉夫堡大学睡眠研究中心(Sleep Research Centre)主任吉姆?霍恩(Jim Horne)引用上述这段社评，是为了证明目前担心西方人在累积不健康“睡眠债”的风潮毫不新鲜。
100多年后，科学和大众媒体的文章再一次声称，工作和休闲的需求使得很大一部分人长期缺乏睡眠，对劳动生产率、健康和安全造成了破坏性后果。
领先科学期刊《自然》(Nature)近期的一篇社评就很典型，该文抨击了这样一种“错误观念”：因为成功人士可以每晚只睡几个小时，所以睡觉是浪费时间。
“睡眠减少的趋势对公共安全造成了严重后果――工业化国家也许比一个世纪前少20%，”《自然》杂志称。睡眠不足导致了很大一部分公路和铁路车祸及其它事故，比如1989年的埃克森?瓦尔迪兹号(Exxon Valdez)油轮事故。
据美国国家卫生研究院(National Institutes of Health)称，睡眠不足和睡眠失调每年的医疗开支要花掉美国150亿美元，劳动生产率方面的损失则为500亿美元。但越来越多的著名睡眠研究者在反对将睡眠债曲解为一种较新鲜的现象，他们认为这些曲解有商业动机。霍恩教授就是其中一位。另一位是加州大学圣迭戈分校研究教授丹尼尔?克里普克(Daniel Kripke)。“我认为，大多数这种公关宣传活动，都是由那些从安眠药生产或者商业性睡眠诊所赚钱的人操纵的，”他表示。
例如上月，葛兰素史克(GlaxoSmithKline)的安眠药品牌Nytol与英国消费者咨询机构未来实验室(Future Laboratory)发布了一份民意调查报告，报告断定：“睡眠债是一种正在上升的趋势和现象，因为我们决心不断减少睡眠时间，导致了疲惫、注意力不集中和性情暴躁。”报告称，人们应该以“8小时纯睡眠”为目标。
克里普克教授和其他人员所做的大规模人口研究显示，每晚睡7到7.5小时的人死亡率最低；睡眠超过8小时则死亡率大幅上升。“但许多睡眠研究人员似乎认为，7到7.5小时对健康成年人来说是不够的，我们应该多睡一个小时左右，”霍恩教授表示。霍恩教授的著作《Sleepfaring》将于下月出版。
认为我们每晚至少需要8小时睡眠的观念，实际上在让失眠变得更加严重，它让人们产生了不必要的担心，担心自己没睡够8个小时，”克里普克教授表示。他认为，太多睡眠可能是比太少睡眠更严重的健康问题；南卡罗来纳大学正在进行一项临床研究，以弄清楚每晚睡眠超过8.5小时的人，是否会从减少睡眠时间中获益。
霍恩教授表示，认为人们比祖辈睡眠时间少的观点，是基于对旧时调查的误解，特别是对被经常引用的1913年斯坦福大学研究的误解，该项研究关注的是中小学学生的睡眠。
“今天我们更缺少睡眠的说法是完全错误的，”他坚持说。“事实是，大多数人可能睡得更好了，因为卧室的设计相比100年前又透风又嘈杂的房间好多了。”(对加拿大因纽特人的一项研究显示，在电灯出现以前，他们在北极夏季平均睡6小时，冬季则为14时。)
多伦多大学睡眠医学和生物生理调节中心(Centre for Sleep Medicine and Circadian Biology)主任道格拉斯?布拉德利(Douglas Bradley)建议折中了一下。“我认为，与相对平静的20世纪五、六十年代，而不是19世纪相比，我们的社会是睡眠缺乏的，那时不像现在，每个街角都有咖啡店，”他说。“但我同意，存在一些既得利益集团(夸大)睡眠欠债程度的现象。”
霍恩教授表示，多数支持睡眠缺乏论点的实验证据，来自对嗜睡者的问卷和实验室研究，这可能对人产生误导。如果有机会，人们会睡得更多，但这并不意味着他们缺乏睡眠。
而萨里大学(University of Surrey)的睡眠研究者史蒂芬?埃梅格伯(Stephen Emegbo)相信，霍恩和克里普克教授低估了现代社会对睡眠的影响。
“对生活的各方面来说，灯泡都是绝妙的发明，但睡眠除外，”他说。“人们宁愿熬夜到凌晨4、5点钟，努力完成一项工作，而不是好好睡一晚，把工作留到第二天去完成。无论人们是否比过去睡得少，我相信，今天的睡眠中断更多、更破碎，睡眠失调也更多。”
据医药市场咨询机构寰宇药品资料管理公司(IMS Health)的数据，去年，美国睡眠药物处方数量上升了13%，达4300万份。一些睡眠专家对这种增长表示欢迎，他们认为，这反映了这样的事实：医药行业为治疗失眠症提供了上等产品。
其他人对此表示担忧，尽管新药的副作用比上几代睡眠药物更少，但长期使用可能有害――并可能掩盖导致失眠的更基本健康问题。
埃梅格伯博士说：“若服用这些催眠药的时间比计划的4到8周更长，问题就会出现。”
上夜班是患职业性失眠症的重要原因。“大部分上夜班的人长期缺乏睡眠，”布拉德利教授称，“但一些轮班模式比其它形式要好一些。”他自己位于多伦多的实验室里，研究工作要求人员上夜班，那里的工作人员所遵循的模式是：连续上三个12个小时的夜班，接着休息3天，然后是5个连续白班。
对要求8小时长夜班的企业来说，布拉德利教授称，最好的模式是实行早班(上午6点到下午2点)，中班(下午2点到晚上10点)，夜班(晚上10点到早上6点)的翻班：“以这种顺序翻班很重要，因为我们的生物钟天生就有延长白天的倾向。”
我们可以很有把握地预言，在今后的许多年里，失眠仍将是“公众讨论的话题”。
