(单词翻译:单击)
听力文本
Scientists have long said getting a good night's sleep is important to your health.
长期以来，科学家们一直表示，晚上睡个好觉对你的健康很重要。
The U.S. National Institute of Health says lack of sleep may even increase the risk of impaired brain activity, or cognitive decline, and Alzheimer's disease.
美国国立卫生研究院表示，睡眠不足甚至可能增加大脑活动受损（即认知功能下降）以及患阿尔茨海默病的风险。
Now, an American team of scientists reports that too much sleep might be similarly linked to such conditions.
现在，一个美国科学家团队报告说，过多的睡眠可能与这种情况有类似的联系。
Researchers at Washington University School of Medicine in St. Louis, Missouri, did the sleep study.
位于密苏里州圣路易斯市的华盛顿大学医学院的研究人员进行了这项睡眠研究。
Their findings were published in the September issue of the scientific publication Brain.
他们的研究结果发表在科学刊物《大脑》的9月刊上。
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.
该研究对100名成年人进行了平均4.5年的认知能力（即思考能力）的医学观察。
The average age of the study subject was 75.
研究对象的平均年龄为75岁。
Eighty-eight of the group had been identified as free of cognitive impairment, or damage.
其中88人被确认没有认知障碍（即认知损伤）。
Eleven subjects were judged very mildly impaired, and one was identified as mildly impaired.
11名受试者被判定为非常轻微的受损，1名被确认为轻度受损。
During the study, they were asked to complete several tests for signs of cognitive decline.
在该研究期间，他们被要求完成几项针对认知功能下降迹象的测试。
The tests are combined into a cognitive score--the higher the score, the better.
这些测试被合并成一个认知分数——分数越高越好。
They also wore electroencephalography (EEG) devices for four to six nights to measure their brain activity during sleep.
他们还佩戴了四到六个晚上的脑电图（EEG）设备，以测量他们在睡眠期间的大脑活动。
Overall, cognitive scores declined for the groups that slept less than 4.5 hours or more than 6.5 hours per night--as measured by EEG.
总体而言，根据脑电图的测量，每晚睡眠少于4.5小时或超过6.5小时的小组的认知得分有所下降。
But the scores stayed the same for those in the middle of the range.
但那些睡眠时间处于中间区间的人的分数保持不变。
Dr. Brendan Lucey is director of the Washington University Sleep Medicine Center and led the research.
布伦丹·露西博士是华盛顿大学睡眠医学中心的主任，也是这项研究的负责人。
He said, "Our study suggests that there is a middle range, or 'sweet spot,' for total sleep time" for best cognitive performance.
他说：“我们的研究表明，最佳认知表现对应的总睡眠时间存在一个中间区间，即‘最佳点’”。
"Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality, " Lucey added.
露西还说：“睡眠时间短或长都与认知表现差有关，这可能是因为睡眠不足或睡眠质量差。”
Greg Elder is a sleep researcher at Northumbria University in New Castle, Britain.
格雷格·埃尔德是英国纽卡斯尔诺森比亚大学的睡眠研究员。
He was surprised about the findings that sleeping longer than 6.5 hours was linked with cognitive decline.
他对睡眠时间超过6.5小时与认知能力下降有关的研究结果感到惊讶。
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."
他在《谈话》杂志中写道，“当我们考虑到建议老年人每晚睡7到8小时，这个数字是很低的。”
Elder also noted that the research did not consider other information about the individuals studied, including their general health or economic conditions.
埃尔德还指出，这项研究没有考虑有关被研究人员的其他信息，包括他们的一般健康或经济状况。
Other studies have shown that lack of sleep was linked with cognitive decline.
其他研究表明，睡眠不足与认知能力下降有关。
A small 2018 study published in the Proceedings of the National Academy of Sciences found that losing just one night of sleep led to an increase in beta-amyloid production.
2018年发表在《美国科学院院报》上的一项小型研究发现，仅仅一夜不睡就会导致β-淀粉样蛋白的生成增加。
Beta-amyloid is a metabolic waste product found in between brain cells.
β-淀粉样蛋白是一种存在于脑细胞之间的代谢废物。
It has been long linked to brain disorders, such as Alzheimer's disease.
长期以来，人们一直认为它与阿尔茨海默症等脑部疾病有关。
The National Sleep Foundation advises that healthy adults need between seven and nine hours of sleep per night.
国家睡眠基金会建议，健康的成年人每晚需要7到9个小时的睡眠。
Babies, young children, and teens need even more sleep for their growth and development.
婴儿、幼儿和青少年需要更多的睡眠来促进他们的生长发育。
And people over 65 should also get seven to eight hours per night, the foundation says.
该基金会表示，65岁以上的人每晚也应该有7到8个小时的睡眠时间。
One unanswered question from the Washington University study is whether increasing sleep time for short sleepers would help their cognitive performance.
华盛顿大学的这项研究的一个悬而未决的问题是，增加短睡者的睡眠时间是否会有助于改善他们的认知表现。
But lead writer Lucey said each person's sleep needs are individual.
但主要作者露西说，睡眠需求是因人而异的。
If people feel rested, there is no need to change how they sleep.
如果人们感到休息好了，就没有必要改变他们的睡眠方式。
But those who are not sleeping well should know that sleep problems often can be treated, Lucey said.
露西说，但那些睡眠不好的人应该知道睡眠问题通常是可以治疗的。
Dr. David Holtzman, another top researcher on the study, added, "It suggests that sleep quality may be key, as opposed to simply total sleep."
该研究的另一位首席研究员戴维·霍尔茨曼博士补充说：“这表明睡眠质量可能是关键，而不是简单的完全睡眠。”
I'm Caty Weaver.
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