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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. “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 caffcinated 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 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 body’s 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.

答案與題解 :

1. C pick-me-up指提神飲料，也就是一種剌激物，在這篇文章里具體指咖啡。所以，答案應(yīng)選 C。

2. C 第二段的第三個句子談到，“控制我們睡眠的是神經(jīng)激素”，而這一段的昀后一個句子也告訴我們“含咖啡因咖啡能使這種睡眠激素減半”。這正是咖啡因影響睡眠的原理。

3. A第三段涉及的是一個實驗，這個實驗的目的是測試含咖啡因咖啡和脫咖啡因咖啡對睡眠的影響，該段主要談?wù)摰氖沁@個實驗的結(jié)果。

4. D 第四段是第三段實驗的繼續(xù)，是該實驗的第二個階段。研究人員通過對志愿者尿樣進行化驗發(fā)現(xiàn)，咖啡因攝入者體內(nèi)的褪黑激素僅為非咖啡因攝入者的一半。褪黑激素就是睡眠激素，所以，答案應(yīng)該選 D。

5. B 文章的結(jié)尾談到， “Ohayon建議愛喝咖啡的人午飯后應(yīng)該換喝脫咖啡因咖啡”。另外，整個文章都在探討咖啡因影響睡眠的機理，所以，作者大概會同意“晚飯后不應(yīng)該喝咖啡”的說法。選項 A是一個全稱判斷，這等于說“所有喜歡喝咖啡的人都比不喝咖啡的人睡覺少”。這不一定，因為如果咖啡適量，喝咖啡的時間適當(dāng)，咖啡不會影響睡眠。所以，作者可能不會同意這種說法。根據(jù)文章第二段第二個句子，選項 C是錯的。根據(jù)文章第二段的第一個句子，我們體內(nèi)褪黑激素 (睡眠激素 )的濃度在我們上床時間前兩個小時開始上升，而這個時候我們會開始有困意。反過來說就是，人們并非一有困意就睡覺。所以，選項 D不是答案。

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