Napping May Improve Learning, Memory
From VOA Learning English, this is the Health & Lifestyle Report.
March 16 is International Sleep Day.
And we should all celebrate the act of sleeping. Studies have shown that a good night's rest helps us stay healthy, both mentally and physically. And researchers say sleep is probably the best tool we have for memory and learning.
Michael Twery is director of the National Center on Sleep Disorders Research at America's National Institutes of Health. Twery is an expert on the science of sleep and sleep disorders. He told me that a good night's sleep helps to learn better.
"Getting a good night's sleep is important for the learning and memory process. It's important because it stores the training exercises and the learning exercises into our more permanent memory while we're sleeping 7-8 hours in bed. And then the next morning when you wake up your mind is better prepared to act on that information."
But what about getting rest during the middle of the day? Short periods of sleep may help our brains work better, or so says a recent study on napping.
Past studies have shown that napping can help babies and young children learn better. And napping can help brain performance in older adults.
Taking a nap may also help this group of people fight off age-related memory loss.
Many Americans do nap. But one-third of all adults in the United States are also chronically tired, notes the U.S. Centers for Disease Control and Prevention (CDC). It found that 50 million to 70 million Americans have chronic sleep disorders.
So, someone who naps as a way of paying off a sleep debt may not experience the same improvements from napping as a healthy, well-rested person would.
Also, many people may not want to admit that they take a nap. They may think that napping shows they are weak or lack energy. That only children, the very old, sick or lazy people nap is not an uncommon opinion.
In fact, we Americans sometimes do a very strange thing. Some brag about how few hours of sleep they need each night.
Health experts suggest that adults get seven to eight hours of sleep each night. People who claim they only sleep five hours a night, they may think they are somehow stronger than the average human – superhuman, if you will.
However, that may be changing. Many offices now offer napping rooms and napping cafes are appearing in many U.S. cities, including Washington, D.C.
While resting in the middle of the work day may seem like a luxury to Americans, napping is very much part of a normal, everyday life in other parts of the world.
The China sleep study
Take China, for example. While it depends on the age and job, China, generally speaking, is a land of nappers.
So, researchers recently looked at information provided by nearly 3,000 Chinese adults, aged 65 years or older. They wanted to learn if napping after a mid-day meal, a tradition in some areas, had any effect on the mental performance of the subjects.
First, the researchers asked the people if they napped and for how long. Then, based on their answers, researchers put them into four groups: non-nappers (0 minutes), short nappers (less than 30 minutes), moderate nappers (30-90 minutes), and extended nappers (more than 90 minutes).
Nearly 60 percent of those 3,000 people said they did take a nap after lunch and that their naps lasted anywhere from 30 to 90 minutes. Most of the subjects who said they napped said they napped for about an hour.
The study found that people who took an hour-long nap did much better on mental tests than those who did not nap. The hour-long nappers also did better on the tests than those who napped for shorter and longer periods. In this study, it seems that the most effective nap lasted for about an hour, but not much longer.
These researchers reported their findings in the Journal of the American Geriatrics Society.
Keep in mind, however, that these are the findings for those over the age of 65.
Yet Doctor Michael Twery notes that an hour long nap may be too long for young, healthy adults.
"Currently, we're recommending that we try to sleep for about 30 minutes or less. And 30 minutes is enough to remove the pressure to sleep and will help us feel more awake. If we nap longer, we will get trapped into those deeper layers of sleep, which can be hard to get out of."
The feeling Twery described is called sleep inertia -- the period when you awake from a very deep sleep. For a time, you are unable to think clearly.
"So sleep inertia is when someone is being awakened from deep sleep. Some individuals may find it hard to change instantly from that deep sleep – where everything is a bit foggy and confused – to the fully awake state. We may be a little bit clumsy. We may not have all our thoughts in order when we wake from deep sleep."
The National Sleep Foundation also warns that if you have trouble falling asleep at night, limit your daytime nap to under 45 minutes. Also nap before 3 p.m. in the afternoon.
And that's the Health & Lifestyle report.
I'm Anna Matteo.
1.paying off 偿还；补偿
Many financial planners now recommend against ever fully paying off your home loan.
2.deep sleep 深度睡眠
I hate being wakened from a deep sleep by a loud bell.
3.falling asleep 入睡
He tossed about in bed for hours before falling asleep.
4.take a nap 睡午觉
Get in the back seat and take a nap while I drive.
5.Keep in mind, however, that these are the findings for those over the age of 65.
Keep in mind 记住
Keep in mind you're going to be fighting lots of men who hit plenty hard.
I hope he grew up, also keep in mind: Our ancestors are Chinese.
6.For a time, you are unable to think clearly.
For a time 暂时；一段时间
I think you ought to give football a rest for a time.
The ship drifted helplessly for a time.
我们都应提倡睡觉这一行为 。研究表明，晚间良好的睡眠有助于保持身心健康 。研究人员指出，睡眠可能是我们记忆与学习的最佳工具 。
迈克尔·特维里（Michael Twery）是美国国立卫生研究院睡眠紊乱研究中心的主任 。他也是睡眠与睡眠障碍科学方面的专家 。他告诉我，一夜好眠有助于学习 。
“睡个好觉对于学习和记忆过程十分重要 。因为当我们睡足七八个小时后，睡眠能够更加长久地储存我们学习和训练的活动 。当第二天早起后，你的大脑能更好地处理那些信息 。”
此前，有研究表明，婴幼儿午休有助于提高其学习能力 。而对于年纪稍长的成年人来说，午休有助于大脑更好地运转 。
许多美国人都选择午休 。不过，美国疾病控制和预防中心指出，三分之一的美国成年人都存在慢性疲劳症状 。该中心还指出，约5000万到7000万的美国人患有慢性睡眠紊乱症 。
而且，很多人不想承认他们的午休习惯 。或许，他们认为午休意味着身体虚弱，缺乏精力 。人们普遍认为，只有老、弱、病、懒的人才会午睡 。
其实，美国人有时会有个奇怪的癖好 。有人会吹嘘晚上睡眠的时间短 。
健康专家建议成年人每晚睡七到八个小时 。那些声称每晚只睡四五个小时的人，他们可能自认为比普通人更加强壮——或者说是超人 。
然而，今非昔比 。美国华盛顿等许多城市的办公室都提供了午休室和午休咖啡馆 。
因此，研究人员近期查阅了近3000名65岁及以上的中国成年人所提供的信息 。他们想知道，很多地区视午睡为传统，那么用餐后午睡是否对身体有影响 。
首先，研究人员调查这些受访者是否午睡以及午睡时间 。之后根据他们的回答将其分为四组：不午睡者，午睡时间短者（少于30分钟），睡眠时间适中者（30-90分钟）以及午睡时间长者（超过90分钟） 。
在3000位受访者中，约60%的人表示，午饭后会午休30到90分钟 。大多数午睡的人称，一般会休息一个小时左右 。
研究发现，午休一小时者的体能测验结果比不午休的人好很多 。而午睡一小时者比午休时间短于或长于一小时者的测验结果更佳 。这项研究显示，似乎最佳睡眠时长为一小时左右，不宜睡太久 。
不过特维里博士指出，对于身体健康的年轻人来说，午休一小时可能太久了 。“目前，我们建议的午睡时长为30分钟甚至更短，30分钟足够消除睡眠压力，也能让我们更加清醒 。如果午睡时间太久，容易进入深度睡眠，很难清醒过来 。”
特维里所说的这种感觉名为“睡眠惯性”——从深度睡眠中苏醒的时间段 。你的头脑暂时无法清晰地思考 。
“所以睡眠惯性就是人们从深度睡眠中苏醒，有人发现很难从深度睡眠中立即调整好状态 。或许我们有一些迟钝 。从深度睡眠中苏醒时，我们的思维有些混乱” 。
美国国家睡眠基金会警告称，如果晚上入睡困难，可以把午睡的时间控制在45分钟之内 。此外，尽量在下午三点前午睡 。