VOA慢速英语--研究表明长时间睡眠和认知丧失之间存在联系

Study Suggests Link Between Long Sleep Times, Cognitive¹ Loss

Scientists have long said getting a good night's sleep is important to your health. The U.S. National Institute of Health says lack of sleep may even increase the risk of impaired² brain activity, or cognitive decline, and Alzheimer's disease.

Now, an American team of scientists reports that too much sleep might be similarly linked to such conditions.

Researchers at Washington University School of Medicine in St. Louis, Missouri, did the sleep study. Their findings were published in the September issue of the scientific publication Brain.

The study examined 100 adults who had been under medical observation for cognitive ability, the ability to think, for an average of 4.5 years. The average age of the study subject was 75. Eighty-eight of the group had been identified as free of cognitive impairment, or damage. Eleven subjects were judged very mildly impaired, and one was identified as mildly impaired.

During the study, they were asked to complete several tests for signs of cognitive decline. The tests are combined into a cognitive score – the higher the score, the better. They also wore electroencephalography (EEG) devices for four to six nights to measure their brain activity during sleep.

Overall, cognitive scores declined for those who slept less than 4.5 hours or more than 6.5 hours per night — as measured by EEG. But the scores stayed the same for those in the middle of the range.

Dr. Brendan Lucey is director of the Washington University Sleep Medicine Center and led the research. He said, "Our study suggests that there is a middle range, or ‘sweet spot,' for total sleep time" for best cognitive performance.

"Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient³ sleep or poor sleep quality, " Lucey added.

Greg Elder is a sleep researcher at Northumbria University in New Castle, Britain. He was surprised about the findings that sleeping longer than 6.5 hours was linked with cognitive decline. He wrote in The Conversation, "this is low when we consider that older adults are recommended to get between seven and eight hours of sleep every night."

Elder also noted⁴ that the research did not consider other information about the individuals studied, including their general health or economic conditions.

Earlier findings

Other studies have shown that lack of sleep was linked with cognitive decline. A small 2018 study published in the Proceedings⁵ of the National Academy of Sciences found that losing just one night of sleep led to an increase in beta-amyloid production. Beta-amyloid is a metabolic⁶ waste product found in between brain cells. It has been long linked to brain disorders⁷, such as Alzheimer's disease.

The National Sleep Foundation advises that healthy adults need between seven and nine hours of sleep per night. Babies, young children, and teens need even more sleep for their growth and development. And people over 65 should also get seven to eight hours per night, the foundation says.

One unanswered question from the Washington University study is whether increasing sleep time for short sleepers⁸ would help their cognitive performance.

But lead writer Lucey said each person's sleep needs are individual. If people feel rested, there is no need to change how they sleep. But those who are not sleeping well should know that sleep problems often can be treated, Lucey said.

Dr. David Holtzman, another top researcher on the study, added, "It suggests that sleep quality may be key, as opposed to simply total sleep."

Words in This Story

cognitive decline - n. experience of worsening or more frequent confusion or memory loss

impairment - n. a condition in which a part of your body is damaged

sweet spot - n. an ideal or most favorable factor for particular activity or purpose

associate - v. to think of one thing when you think of another

recommend - v. to suggest that someone do something

metabolic - adj. related to a chemical process that grows and heals

key - n. something that is necessary in order to achieve something

1 cognitive   

adj.认知的，认识的，有感知的

参考例句：

• As children grow older,their cognitive processes become sharper.孩子们越长越大，他们的认知过程变得更为敏锐。
• The cognitive psychologist is like the tinker who wants to know how a clock works.认知心理学者倒很像一个需要通晓钟表如何运转的钟表修理匠。

2 impaired   

adj.受损的；出毛病的；有（身体或智力）缺陷的v.损害，削弱( impair的过去式和过去分词 )

参考例句：

• Much reading has impaired his vision. 大量读书损害了他的视力。 来自《现代汉英综合大词典》
• His hearing is somewhat impaired. 他的听觉已受到一定程度的损害。 来自《现代汉英综合大词典》

3 insufficient   

adj.(for，of)不足的，不够的

参考例句：

• There was insufficient evidence to convict him.没有足够证据给他定罪。
• In their day scientific knowledge was insufficient to settle the matter.在他们的时代，科学知识还不能足以解决这些问题。

4 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

5 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

6 metabolic   

adj.新陈代谢的

参考例句：

• Impressive metabolic alternations have been undergone during embryogenesis.在胚胎发生期间经历了深刻的代谢变化。
• A number of intoxicants are associated with metabolic acidosis.许多毒性物质可引起代谢性酸中毒。

7 disorders   

n.混乱( disorder的名词复数 )；凌乱；骚乱；（身心、机能）失调

参考例句：

• Reports of anorexia and other eating disorders are on the increase. 据报告，厌食症和其他饮食方面的功能紊乱发生率正在不断增长。 来自《简明英汉词典》
• The announcement led to violent civil disorders. 这项宣布引起剧烈的骚乱。 来自《简明英汉词典》

8 sleepers   

n.卧铺（通常以复数形式出现）；卧车( sleeper的名词复数 )；轨枕；睡觉（呈某种状态）的人；小耳环

参考例句：

• He trod quietly so as not to disturb the sleepers. 他轻移脚步，以免吵醒睡着的人。 来自辞典例句
• The nurse was out, and we two sleepers were alone. 保姆出去了，只剩下我们两个瞌睡虫。 来自辞典例句