Study Suggests Link Between Long Sleep Times, Cognitive Loss
2021-11-16
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1Scientists have long said getting a good night's sleep is important to your health.
2The 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.
3Now, an American team of scientists reports that too much sleep might be similarly linked to such conditions.
4Researchers at Washington University School of Medicine in St. Louis, Missouri, did the sleep study.
5Their findings were published in the September issue of the scientific publication Brain.
6The study examined 100 adults who had been under medical observation for cognitive ability, the ability to think, for an average of 4.5 years.
7The average age of the study subject was 75.
8Eighty-eight of the group had been identified as free of cognitive impairment, or damage.
9Eleven subjects were judged very mildly impaired, and one was identified as mildly impaired.
10During the study, they were asked to complete several tests for signs of cognitive decline.
11The tests are combined into a cognitive score - the higher the score, the better.
12They also wore electroencephalography (EEG) devices for four to six nights to measure their brain activity during sleep.
13Overall, 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.
14But the scores stayed the same for those in the middle of the range.
15Dr. Brendan Lucey is director of the Washington University Sleep Medicine Center and led the research.
16He said, "Our study suggests that there is a middle range, or 'sweet spot,' for total sleep time" for best cognitive performance.
17"Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality, " Lucey added.
18Greg Elder is a sleep researcher at Northumbria University in New Castle, Britain.
19He was surprised about the findings that sleeping longer than 6.5 hours was linked with cognitive decline.
20He 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."
21Elder also noted that the research did not consider other information about the individuals studied, including their general health or economic conditions.
22Other studies have shown that lack of sleep was linked with cognitive decline.
23A 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.
24Beta-amyloid is a metabolic waste product found in between brain cells.
25It has been long linked to brain disorders, such as Alzheimer's disease.
26The National Sleep Foundation advises that healthy adults need between seven and nine hours of sleep per night.
27Babies, young children, and teens need even more sleep for their growth and development.
28And people over 65 should also get seven to eight hours per night, the foundation says.
29One unanswered question from the Washington University study is whether increasing sleep time for short sleepers would help their cognitive performance.
30But lead writer Lucey said each person's sleep needs are individual.
31If people feel rested, there is no need to change how they sleep.
32But those who are not sleeping well should know that sleep problems often can be treated, Lucey said.
33Dr. David Holtzman, another top researcher on the study, added, "It suggests that sleep quality may be key, as opposed to simply total sleep."
34I'm Caty Weaver.
1Scientists 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 impaired brain activity, or cognitive decline, and Alzheimer's disease. 2Now, an American team of scientists reports that too much sleep might be similarly linked to such conditions. 3Researchers 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. 4The 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. 5During 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. 6Overall, 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. But the scores stayed the same for those in the middle of the range. 7Dr. 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. 8"Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality, " Lucey added. 9Greg 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." 10Elder also noted that the research did not consider other information about the individuals studied, including their general health or economic conditions. 11Earlier findings 12Other studies have shown that lack of sleep was linked with cognitive decline. 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. Beta-amyloid is a metabolic waste product found in between brain cells. It has been long linked to brain disorders, such as Alzheimer's disease. 13The 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. 14One unanswered question from the Washington University study is whether increasing sleep time for short sleepers would help their cognitive performance. 15But 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. 16Dr. David Holtzman, another top researcher on the study, added, "It suggests that sleep quality may be key, as opposed to simply total sleep." 17I'm Caty Weaver. 18Hai Do wrote this story for Learning English. Caty Weaver was the editor. 19_________________________________________________ 20Words in This Story 21cognitive decline - n. experience of worsening or more frequent confusion or memory loss 22impairment - n. a condition in which a part of your body is damaged 23sweet spot - n. an ideal or most favorable factor for particular activity or purpose 24associate - v. to think of one thing when you think of another 25recommend - v. to suggest that someone do something 26metabolic - adj. related to a chemical process that grows and heals 27key - n. something that is necessary in order to achieve something