吕文新：译自《新西兰先驱报》登载的梅西大学《睡眠与清醒研究中心》研究员凯瑞博士的科普文章。
From nzherald
传言一：你并不需要每晚睡八个小时
你可能听过某人说自己“天生觉少”。然而，这种说法却没有任何科学根据。
研究显示：睡觉少于七个小时的人与睡满八小时的人相比,大脑反应速度略慢、肢体动作不够协调、创造力不足、容易做出错误决定、脾气不够好、不易与人相处。
这项研究还显示：我们不易察觉到缺觉所带来的伤害，若长期缺觉，肯定会带来健康问题。
而那些睡觉少于六个小时的人，可能会患上肥胖症、2型糖尿病、心脏病或中风。
传言二：平时缺的觉可以在周末补回来
周一到周五，我们都在忙着工作、忙着家务、忙着交际，不得不牺牲一些睡眠时间。研究显示，在长周末或串休时，大睡两到三天，虽然会补回一些睡觉时间，但补不足每天七到九小时的睡眠质量。而缺觉所欠下的“睡眠债”会持续造成影响，以至于周一上班时也提不起精神。
传言三：开车犯困时，对着脸上吹凉风会提神
我们都听说过某些对付开车时犯困的妙招。比如把车内音响的声音调大，对着脸上吹凉风等。
其实，如果你已经困得不行，这样的办法只能帮你挺一小会儿。你很快就会在不知不觉中睡过去。
黄金法则是，不打无准备之仗。开长途的头一天晚上要睡好、仅在白天头脑清醒时开车、并且开一会儿就停下来歇一会儿。若每天下班时开车常犯困，最好先在车里眯20到40分钟，或在下班前15到30分钟时喝一杯咖啡提提神。若开车时困劲真上来了，一定要马上停车，打个盹，或另选别的出行方式。
传言四：夜里醒来就是睡得不好
有些人认为，半夜若是醒来，则整个晚上的睡眠都被毁了。这种说法绝对不靠谱。实际上，这是一种很自然的现象。人体自古就在睡眠周期中，夹有两到三个小时的“清醒”时间，这种现象不会对身体健康造成任何负面影响，我们还是能得到八个小时的睡眠时间。如果你现在每晚醒一到三次，都是很正常的，翻个身接着睡吧。
但是，若醒的次数过多，则意味着你的睡眠环境可能有问题，也可能是你患上了某种疾病，若那样的话，应该马上就医。
传言五：老年人觉少
我们的睡眠时间确实随着年龄的增长而改变。
当过父母的人都知道，婴儿比成人睡的多，睡眠周期也不一样。而在儿童期，青春期和成人期的成长过程中，睡眠周期一直在变化中。最显著的变化发生在儿童期和青春期之间。
半夜里，老年人比年轻人更容易醒来，因此，老年人更应该确保七到九个小时的睡眠时间以让身体保持最佳状态。
令人不解的是，虽然老年人由于缺觉而受到了明显的健康损害，但他们也确实也比年轻人更能适应缺觉所带来的负面影响。
传言六：青少年的睡眠习惯是懒惰造成的
青少年晚上不睡，早上不起，是每个家庭都曾经历过的问题，并经常归咎于懒惰。实际上，这是由于青少年体内的生物钟造成的生理变化。
青春期时，他们体内的生物钟会比大自然的白天和黑夜的时间略晚一些，推迟了上床和起床的时间，使得孩子们即使上了床也睡不着，天亮了也醒不过来。更何况，现在的孩子们大多有了自己的房间，自己的社交圈，再加上学校作业的负担，使得他们在上学期间，睡眠一直不足。
这种现象在短期内，会导致他们学业不佳、记忆力下降、注意力下降、信息处理能力不足、情绪低落，进而引发行为异常。长此以往，可能会导致肥胖及坏胆固醇增高，还有可能把这种坏习惯带到成人期。
传言七：人类还不能确定睡眠是否有用
睡眠不足的人可能会这样安慰自己：睡觉对人体健康并没有明显功效。并且，我们最常听到的说法是：睡觉只不过是让大脑和身体进入“休眠”状态，等同于“休息”。这种说法早已经过时了。实际上，我们的大脑在睡眠状态下依然活动频繁，大脑的某些部位甚至比清醒时活动得还要频繁。
大规模的调查和实验显示，睡眠对人类健康和体能优化起着至关重要的作用，而且某些优化过程仅在睡眠时才发生。比如，神经系统之间的连接部位，只有在我们入睡后，才有机会得以加固。大脑利用这个机会，巩固对知识的记忆、优化记忆空间的使用，同时还把有可能对大脑造成长期损害的蛋白质排出去。
传言八：晚上喝酒有助睡眠
酒精确实能让我们很快入睡，但最终会破坏我们的睡眠质量。
有些人可能对自己的醉态还有一点儿印象：躺倒了就睡，睡姿一夜不变，就像死狗一样。可是却不断地被惊醒，心跳过速，胃肠不适，呼吸不畅，还有可能做噩梦。
酒精会改变我们的睡眠结构周期。当我们的身体全力以赴地分解酒精时，睡眠的“快速眼动睡眠期”就会被缩短。（百度：人们正常的睡眠结构周期分两个时相：“非快速眼动睡眠期”和“快速眼动睡眠期”。两者交替出现，交替一次称为一个睡眠周期，两种循环往复，每夜通常有 4~5个睡眠周期，每个周期90~110分钟。）缺失的时间被记到账上，一旦酒精被分解完毕，我们的大脑就开始集中补时了。其后果是，“快速眼动睡眠期”占了主导地位，导致神经系统异常活动，引发上述各种问题。
总之，你喝进身体里的酒精越多，喝酒时间与睡眠时间越近，你的睡眠质量受到的影响就越大。
传言九：早起的鸟儿有虫吃
这个比喻表面上是说早起的鸟儿能吃饱，其实是暗指早起的人儿能有机会做更多的事，从而，取得成功。
然而，说这句话的前提是，这位早起的人儿在前一天晚上已经睡足了觉，并且此人是个真正的天生早鸟。天生是早鸟的人，睡得早也醒得早，从来不需要像普通人那样，需要靠闹钟才能早起。但这里需要强调的是，为了早起而缩短睡眠时间，不会给人带来任何益处。至今也没有证据显示，早鸟儿们比普通人有任何优势。
怎样才能知道自己每天需要多少睡眠时间呢？什么时候是自己的“自然睡”和“自然醒”的时间呢？
选一个两周的假期，把自己的卧室整理得舒舒服服，不要设置闹铃，然后开始记录。
第一周，你的睡眠时间可能还在延续你上班时的习惯。第二周测出的时间，才是你天生的睡眠习惯。
传言十：睡前使用手机或平板电脑不会影响睡眠
使用发光屏幕的电子设备会使人在想睡觉时睡不着，还会影响睡眠质量。
我们周边的环境光，是人体生物钟判定何时是白天的依据。明亮的光线会提醒我们的身体说：现在是白天，不要睡觉。可是，我们如今爱不释手的各种电子产品，大多都会发出亮光，而且，亮光中主要是蓝光。
偏巧是蓝光对人体生物钟的影响最大。研究显示，蓝光对人类睡眠时间有非常大的影响。例如，在睡前两小时使用有发光屏幕的电子书，会把入睡时间推迟一个小时。把开着的手机留在卧室里，更可能造成对睡眠的干扰。各种推送或提醒会把你从梦中叫醒，你若起身查看推送的内容，你就会曝露在蓝光下。尤其你若是在后半夜一两点钟还干这样的傻事，那你就别想睡好了，你的睡眠周期也会被彻底改变了。
吕文新
2017年元旦译于新西兰奥克兰
原文：Busting the bed-time myths
Dr Karyn O'Keeffe, PhD, is a Research Fellow at the Sleep/Wake Research Centre, Massey University. She began her career as a clinical sleep physiologist and transitioned in research and lecturing on sleep and circadian science. Her research interests include managing fatigue in healthcare professionals, treatment provision for sleep disorders, and improving sleep health for the general population.
Myth 1 - You don't really need eight hours' sleep a night
Most of us know someone who claims that they can get away with very little sleep.
However, these claims are not backed up by science.
Studies show that compared to individuals who get eight hours' sleep, those who get less than seven hours' sleep a night have slower reaction times, are unco-ordinated, are less creative, make poorer decisions, have poor moods and don't get on as well with others.
Research also shows that we are not aware of our own level of impairment.
In the long term, short sleep can lead to health problems.
Those who get less than six hours' sleep a night have a higher risk of putting on weight, developing type 2 diabetes and heart disease, and suffering a stroke.
Fortunately, our national surveys of New Zealanders have shown that most of us do get between seven to nine hours' sleep on average.
Concerning, though, is that about a quarter of New Zealanders get six hours or less sleep each night.
Myth 2 - You can catch up on lost sleep at the weekend
Weekdays are full with work, family and social commitments, and sleep is often sacrificed.
Many of us aim to catch up on any lost sleep at the weekend.
However, research shows this is not as achievable as we think.
Missing out on sleep during the week leads to a continual decline in functioning.
Sleeping in on Saturday or Sunday leads to an improvement in this functioning, but we don't seem to return to the optimal levels we experience when we are getting seven to nine hours' sleep - even after two to three days of catch-up at the weekend.
Depending on how short we have been cutting our sleep, this can mean we start the next week with a sleep debt - and arrive at work behind the eight ball.
Myth 3 - Blasting cold air in your face will keep you awake if you're feeling sleepy while driving
There are plenty of strategies that we try to keep ourselves awake when driving.
These might include turning up the radio or blasting cold air in our faces. What we know is that these strategies work in the short term, but are not an effective way to keep yourself awake if you're feeling really sleepy.
The golden rule is, if you are too sleepy you will fall asleep uncontrollably. So the best strategy is to start your trip in the best possible position.
Get a full night's sleep before you go, drive during daylight hours to be most alert, and stop and take regular breaks.
If you are feeling drowsy while driving home from work, consider a short 20- to 40-minute nap before you head home and drink a cup of coffee 15 to 30 minutes before you leave to give yourself a brief caffeine kick. If sleepiness becomes overwhelming, stop as soon as you can and take a nap, or find another way to get where you're going.
Myth 4 - Waking up during the night means you're not getting good quality sleep
There is definitely a myth that waking up during the night means that your sleep is abnormally broken.
In fact, it is quite normal to wake overnight.
Historically, individuals would experience a longer sleep period following the natural day and night cycle, with a two-to-three hour period of wakefulness in the middle of the night between two sleep periods, without any impairment.
Importantly, people still obtained approximately eight hours' sleep in total each night.
In today's society, it is quite normal to wake one to three times overnight, roll over and go back to sleep.
Waking more frequently than this may mean there is something in your sleeping environment that is causing you to wake, or you may have a medical issue that is disrupting your sleep.
If you suspect the latter, have a chat with your GP.
Myth 5 - Older people need less sleep
Our sleep changes substantially across the lifespan.
As any parent will know, young infants need much more sleep than adults and have a mind of their own when it comes to a sleep routine.
As we progress through childhood, adolescence and adulthood, our sleep structure and timing continues to change.
The most dramatic changes are seen between birth and the end of adolescence.
While the sleep of older adults may be more broken and the structure of their sleep slightly different to younger adults, in general older adults still need seven to nine hours' sleep a night to function at their best.
Curiously, although older adults show clear impairment when they don't get enough sleep, they appear to be slightly more resilient to sleep loss than younger adults.
Myth 6 - The sleep habits of teenagers are the result of laziness
It is no secret that teenagers like to go to bed late and sleep in as much as they can each morning.
These habits are often attributed to laziness, but are actually a result of biological changes in the way the circadian body clock functions in teenagers.
In adolescence, our internal body clock shifts later relative to the natural day and night cycle, resulting in a biological preference for later bed and wake times.
The practicalities of this mean that teenagers are unable to fall asleep when they want to and find it difficult to get out of bed in the morning.
This, combined with increasing independence, social activity and school demands, can lead to short sleep on school nights.
Approximately 21 per cent of New Zealand teenagers do not get enough sleep - about eight or nine hours each night, compared with their biological sleep need, which is approximately nine to 10 hours.
Our studies on New Zealand teenagers have also highlighted that there is a large discrepancy between bed times on school nights (10.30pm) and weekends (midnight).
In the short term, insufficient sleep in teenagers leads to poor academic performance - poor memory, information processing and attention span - poor mood, and increased risky behaviour.
In the long term, it may lead to increased weight and cholesterol, as well as behavioural sleep habits that continue into adulthood.
Myth 7 - We don't know anything about the functions of sleep
It may be easier to justify cutting sleep short when it doesn't appear to have any particular function.
Many of us will have heard that it is more putting the body and brain into hibernation mode so that we can "rest".
This view is now quite outdated.
The brain is very active during sleep, and some parts of the brain more so than during wakefulness.
Experimental and large population studies have highlighted that sleep is crucial for good health and optimal functioning.
Some processes are unique to sleep and cannot happen at any other time.
For example, connections between neurons are strengthened during sleep.
We consolidate memories and optimise our capacity for learning during sleep, and our brain is flushed of harmful proteins that can lead to long-term damage.
Myth 8 - Drinking alcohol in the evening will help you sleep
Alcohol certainly helps us get off to sleep easily but is ultimately harmful to our sleep.
Any of us who have overindulged in alcohol will recall sleeping like a log in the first portion of the night, but then experiencing a fitful night of frequent awakenings, racing heartbeats, stomach upsets and, potentially, bad dreams.
Alcohol changes the structure of our sleep, such that we have very little REM (rapid eye movement) sleep while we are processing alcohol.
The downside to this is that we experience a "REM withdrawal" and once we have processed all alcohol, our sleep is predominantly made up of REM sleep.
REM sleep is a sleep stage associated with variable sympathetic nervous system activity, which leads to broken sleep, as well as frequent changes in the body's processes such as heart rate and breathing.
There's a simple rule when it comes to alcohol; the more we put in our body and the closer to bedtime we consume, the more it affects our sleep.
Myth 9 - The early bird gets the worm
Aside from the obvious metaphor about beating the pack, this might also be interpreted as giving you more opportunity to get things done and, therefore, succeed.
However, in relation to sleep, this would only be true if the early bird also got enough sleep the previous night and the early bird is truly a natural early bird.
It is important to note that cutting your sleep short by waking early does not give you an advantage.
Natural early birds consistently go to bed and wake earlier, rather than setting the alarm to wake early, than the average person.
However, there is no evidence that those who wake earlier function better than those who wake at more usual times.
How can you work out your natural sleep need and timing?
Choose a two-week holiday period, and sleep in an ideal environment without any alarms.
You'll likely catch up on sleep in the first week.
Your sleep habits in the second week are likely your natural sleep habits.
Myth 10 - Using smartphones and tablets before bed has no effect on your sleep
Using devices with bright light emitting screens before bed can make it hard to fall asleep when you want to and affect the quality of your sleep.
Light in our external environment provides information for our circadian body clock about what time of day it is.
Bright light reminds our body clock that it is daytime, which logically does not promote sleep.
Unfortunately, the electronic devices that we are so fond of emit bright light that contains a significant proportion of blue wavelength light.
Blue light happens to have a much stronger influence over our body clock and studies investigating the impact of blue light have shown that it has a profound effect on the timing of our sleep.
Studies have shown that using bright light emitting e-readers for just 30 minutes in the two hours before bed can shift bed times approximately one hour later.
Having a smartphone in the bedroom overnight can lead to additional disruption.
Notifications from smartphones can wake you up and the bright light that we expose ourselves to while checking text messages and emails in the wee hours of the morning may lead to difficulty falling back to sleep and changes in our sleep structure.
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