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共用题干 Late-Night DrinkingCoffee lovers beware .Having a quick"pick-me-up"cup of coffee late in the da...
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Late-Night Drinking
Coffee lovers beware .Having a quick"pick-me-up"cup of coffee late in the day will play havoc with your sleep.As well as being a stimulant,caffeine interrupts the flow of melatonin,the brain hormone that sends people into a sleep.
Melatonin levels normally start to rise about two hours before bedtime.Levels then peak be-tween 2 a.m.and 4 a. m.,before falling again."It's the neurohormone that controls our sleep and tells our body when to sleep and when to wake,"says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body's levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six vol- unteers slept less well after a cup of caffeinated coffee than after drinking the same amount of de-caf（脱因咖啡）.On average , subjects slept 336 minutes per night after drinking caffeinated cof-fee,compared with 415 minutes after decaf. They also took half an hour to drop off-twice as long as usual-and jigged around in bed twice as much.
In the second phase of the experiment,the researchers woke the volunteers every three hours and asked them to give a urine sample,Shilo measured concentrations of a breakdown product of melatonin .The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers.In a paper accepted for publication in Sleep Medicine,the researchers suggest that caffeine blocks production of the enzyme that drives melatonin production.
Because it can take many hours to eliminate caffeine from the body,Ohayon recommends that coffee lovers switch to decaf after lunch. Which of the following tells us how caffeine affects sleep?
Late-Night Drinking
Coffee lovers beware .Having a quick"pick-me-up"cup of coffee late in the day will play havoc with your sleep.As well as being a stimulant,caffeine interrupts the flow of melatonin,the brain hormone that sends people into a sleep.
Melatonin levels normally start to rise about two hours before bedtime.Levels then peak be-tween 2 a.m.and 4 a. m.,before falling again."It's the neurohormone that controls our sleep and tells our body when to sleep and when to wake,"says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body's levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six vol- unteers slept less well after a cup of caffeinated coffee than after drinking the same amount of de-caf（脱因咖啡）.On average , subjects slept 336 minutes per night after drinking caffeinated cof-fee,compared with 415 minutes after decaf. They also took half an hour to drop off-twice as long as usual-and jigged around in bed twice as much.
In the second phase of the experiment,the researchers woke the volunteers every three hours and asked them to give a urine sample,Shilo measured concentrations of a breakdown product of melatonin .The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers.In a paper accepted for publication in Sleep Medicine,the researchers suggest that caffeine blocks production of the enzyme that drives melatonin production.
Because it can take many hours to eliminate caffeine from the body,Ohayon recommends that coffee lovers switch to decaf after lunch. Which of the following tells us how caffeine affects sleep?
参考答案: C
参考解析: pick-me-up指提神饮料，也就是一种刺激物，在这篇文章里具体指咖啡。所以，答案应选B。
由第二段第三句中“It's the neurohormone that controls our sleep and tells our body when to sleep and when to wake”可知，控制我们睡眠的是神经激素。这一段的最后一个句子告诉我们“含咖啡因咖啡能使这种睡眠激素减半”。这正是咖啡因影响睡眠的原理。
第三段涉及的是一个实验，这个实验的目的是测试含咖啡因咖啡和脱咖啡因咖啡对睡眠的影响，该段主要谈论的是这个实验的现象。
第四段是第三段实验的继续，是该实验的第二个阶段。研究人员通过对志愿者尿样进行化验发现，咖啡因摄入者体内的褪黑激素仅为非咖啡因摄入者的一半。褪黑激素就是睡眠激素，所以，答案应该选D。
文章的结尾谈到，"Ohayon建议爱喝咖啡的人午饭后应该换喝脱咖啡因咖啡”。另外由第二段的内容可知，含咖啡因咖啡会使控制睡眠的激素减半，所以，作者大概会同意“晚饭后不应该喝咖啡”的说法。
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