{"text":[[{"start":6.9,"text":"Sleep plays a crucial role in clearing toxic waste such as proteins linked to Alzheimer’s disease from the brain, and smartwatch data could help warn of problems, according to a new scientific review."}],[{"start":19.1,"text":"The cerebral cleaning’s rhythms appear to parallel tiny changes in intervals between heartbeats that can be measured by a wearable wrist device, says the paper published in Science on Thursday."}],[{"start":29.950000000000003,"text":"The study is part of a growing effort to identify the purpose of sleep, and health risks resulting from a lack of it. It found that slumber is needed for essential biological purging — suggesting that skipping it may carry greater risks than feeling below par at work or socially. "}],[{"start":45.7,"text":"“For decades, we thought about sleep primarily in terms of memory and restoration,” said Maiken Nedergaard, the review’s author and a neuroscientist at the University of Rochester in the US."}],[{"start":57.25,"text":"“What is emerging now is the idea that sleep is also a highly organised fluid-transport state that helps maintain brain health. Sleep serves many functions, but I believe brain clearance may be the most fundamental of all.”"}],[{"start":70.7,"text":"The paper focuses on the role of a group of brain-regulating chemicals known as neuromodulators, which include serotonin and dopamine. While these operate largely independently of each other during waking hours to affect mood, attention, learning and behaviour, sleep “reorganises their activity into a co-ordinated brain rhythm”, the study says."}],[{"start":92.45,"text":"Synchronised shifts in neuromodulator levels cause blood vessels to change size and promote the flow of cerebrospinal fluid, which protects the brain against physical shocks and pathogens."}],[{"start":104,"text":"The fluid passes through the so-called glymphatic system — a network discovered by Nedergaard’s team in 2012 that helps clean the brain of potentially harmful waste. These include amyloid-beta and tau proteins that form toxic build-ups in sufferers of Alzheimer’s disease and other dementias."}],[{"start":122.5,"text":"Changes in the levels of the neuromodulator norepinephrine during sleep appear to move in concert with small shifts in the amount of time between heartbeats, Nedergaard said. This so-called heart rate variability can be monitored by a smartwatch and could be an indicator of potentially dangerous disruptions to the nightly process of brain tidying, she added."}],[{"start":143.9,"text":"“The idea remains to be tested experimentally, but an attractive feature of heart rate variability is that it may provide information about sleep quality, not simply sleep duration,” Nedergaard said."}],[{"start":155.20000000000002,"text":"Other experts welcomed the paper as an important contribution to our incomplete understanding of how the brain functions. It added to previous studies suggesting that long-term sleep disruptions might raise a person’s vulnerability to dementia, said Sheona Scales, director of research at the Alzheimer’s Research UK charity."}],[{"start":174.8,"text":"“It also suggests that the brain’s chemical rhythms could one day be a target for future treatment, offering a sense of hope to people living with dementia,” said Scales, who called for more work to probe the possibility and search for possible therapies."}],[{"start":189.55,"text":"The paper’s ideas deserved serious investigation, said Nina Rzechorzek, a clinician scientist at the MRC Laboratory of Molecular Biology Cambridge, although she warned of the “risk of an elegant mechanism becoming prematurely over-interpreted”. She said more evidence was needed from studies in people rather than animals, including into whether other biological factors might be important too."}],[{"start":213.55,"text":"“If we want to understand whether sleep disturbance contributes to chronic brain disorders, we need human experimental models and real-world studies . . . rather than assuming that one pathway explains them all,” she said."}],[{"start":233.90000000000003,"text":""}]],"url":"https://audio.ftcn.net.cn/album/a_1779409666_8647.mp3"}