Late-Night Drinking
Coffee lovers beware. Having a quick pick-me-up cup of coffee1 late in the day will play havoc with2 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 between 2 am and 4 am, before falling again3. Its 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 caffcinated coffee halves the bodys levels of this sleep hormone. Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slept less well after a cup of caffeinated coffee than after drinking the same amount of decal. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, compared with 415 minutes after decal. They also took half an hour to drop off4 - twice as long as usual - and jigged around5 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 suggest6 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.
1. The author mentions pick-me-up to indicate that
A melatonin levels need to be raised.
B neurohormone can wake us up.
C coffee is a stimulant.
D decaf is a caffeinated coffee.
2. Which of the following tells us how caffeine affects sleep?
A Caffeine blocks production of the enzyme that stops melatonin production.
B Caffeine interrupts the flow of the hormone that prevents people from sleeping.
C Caffeine halves the bodys levels of sleep hormone.
D Caffeine stays in the body for many hours.
3. What does paragraph 3 mainly discuss?
A Different effects of caffeinated coffee and decaf on sleep.
B Different findings of Lotan Shilo and a team about caffeine.
C The fact that the subjects slept 415 minutes per night after drinking decaf.
D The proof that the subjects took half an hour to fall asleep.
4. What does the experiment mentioned in paragraph 4 prove?
A There are more enzymes in decaf drinkers urine sample.
B There are more melatonin concentrations in caffeine drinkers urine sample.
C Decaf drinkers produce less melatonin.
D Caffeine drinkers produce less sleep hormone.
5. The author of this passage probably agrees that
A coffee lovers sleep less than those who do not drink coffee.
B we should not drink coffee after supper.
C people sleep more soundly at midnight than at 3 am.
D if we feel sleepy at night, we should go to bed immediately.
答案与题解：
1. C pick-me-up指提神饮料，也就是一种剌激物，在这篇文章里具体指咖啡。所以，答案应选 C。
2. C 第二段的第三个句子谈到，控制我们睡眠的是神经激素，而这一段的昀后一个句子也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。
3. A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结果。
4. D 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。
5. B 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，整个文章都在探讨咖啡因影响睡眠的机理，所以，作者大概会同意晚饭后不应该喝咖啡的说法。选项 A是一个全称判断，这等于说所有喜欢喝咖啡的人都比不喝咖啡的人睡觉少。这不一定，因为如果咖啡适量，喝咖啡的时间适当，咖啡不会影响睡眠。所以，作者可能不会同意这种说法。根据文章第二段第二个句子，选项 C是错的。根据文章第二段的第一个句子，我们体内褪黑激素 的浓度在我们上床时间前两个小时开始上升，而这个时候我们会开始有困意。反过来说就是，人们并非一有困意就睡觉。所以，选项 D不是答案。
译文：在深夜饮咖啡
咖啡爱好者注意了。在深夜喝一杯快速提神的咖啡会严重影响你的睡眠，跟兴奋剂一样，咖啡因会扰乱褪黑激素的自由流动，这种褪黑激素是大脑里促人睡眠的一种荷尔蒙。
在上床睡觉前约 2小时的时候褪黑激素含量开始上升，在凌晨 2点到 4点达到最高值，然后再次下降。加州斯坦福大学斯坦福睡眠流行病学研究中心的 Maurice Ohayon说：控制我们睡眠的是神经激素，它告诉我们的身体什么时候睡觉，什么时候醒来。而以色列的研究人员们发现含咖啡因的咖啡使这种睡眼荷尔蒙浓度降至一半。
LotanShilo和Tel Aviv大学Sapir医学中心的一组人员，在给六位志愿者做试验时发现，他们在饮了咖啡因的咖啡后比饮了脱咖啡因的咖啡后睡眼质量要差。平均来说，在喝了含咖啡因的咖啡后每晚睡眠时间336分钟，而喝了脱咖啡因的咖啡后则睡415分钟。同时他们得花半个小时入睡，是通常情况的两倍，另外，他们在床上辗转次数也要长一倍。
在实验的第二阶段，研究人员每三个小时便叫醒一次志愿者，并叫他们提供尿样。 Shilo检验了他们褪黑激素分解产物的浓度，结果显示，咖啡因摄入者体内的褪黑激素是非咖啡因摄入人者的一半。在《睡眼医学》刊物上发表的文章中,研究人员暗示说，褪黑激素的生成由酶促成，而咖啡因阻止了酶的生成。
因为要花许多小时的时间才能将身体中的咖啡因除去， Ohayon建议咖啡爱好者应在午后换喝脱咖啡因的咖啡。