We spend about one-third of our lives asleep. This may sound like a lot of time，but it is not wasted. Our bodies need sleep to stay healthy. Not getting enough sleep can make us sick.
Sleep and our immune(免疫)system
The immune system protects the body from diseases and infections(传染). Not getting enough sleep hurts this protective system.
The Mayo Clinic is a research hospital in the United States. Its website explains that when we sleep our bodies produce proteins(蛋白质) that support sleep and help us fight infections. They add that infection-fighting antibodies(抗体) are reduced during periods when you don’t get enough sleep.
A new study from the University of Washington in the U.S. seems to confirm this. Dr. Nathaniel Watson was the lead writer of the study. Watson says his study shows that the immune system works best when the body gets enough sleep. For the study，Watson and his team studied 11 pairs of twins. This is an important difference from other sleep studies. Other research did not study twins. Researchers found that the twin who slept less had a weaker immune system.
Watson says his study showed for the first time that a long-term lack(缺乏) of sleep shuts down parts of the immune system. He says parts that move white blood cells around the body are influenced. White blood cells fight infections in the body.
Watson’s study provides more evidence(证据) that sleep is important to“overall health”. And sleep is especially important to immune health.
The researchers published their findings in the magazine Sleep.
How much sleep is enough?
To stay in good health，experts at the Mayo Clinic say that adults should get 7 to 8 hours of sleep. Teenagers need 9 to 10 hours. And school-aged children may need more than 10 hours of sleep a night.
Experts say our sleep becomes poor in our 30s. By the time we reach our 50s，the average person has lost 50 percent of their ability to have a restful sleep. These people also have trouble falling asleep and staying asleep through the night. From middle age on，they say these problems only get worse，and they can influence our health.
Signs you may not be getting enough sleep
●You’re always hungry or you’ve gained weight.
●You have trouble making decisions.
●You have trouble remembering things.
●Your skin doesn’t look good.
●You are having trouble seeing.
1. From the first three paragraphs we know that .
A. it is a waste to spend about one-third of our lives asleep
B. we’ll become seriously ill if we don’t have enough sleep
C. enough sleep does good to infection-fighting antibodies
D. immune system is protected when people begin to sleep
2. From Watson’s study，we know .
A. enough sleep helps the immune system work well
B. the study of twins is a kind of common sleep study
C. twins need less sleep but have stronger immune system
D. sleeping for a long time is important to immune health
3. Which of the following is right according to the passage?
A. People don’t need 7 to 8 hours of sleep a night in their fifties.
B. The less you sleep every night，the more weight you’ll lose.
C. Teenagers should get more than 10 hours of sleep a night.
D. If your memory gets worse，you may not get enough sleep.
4. What will probably be written in the following part?
A. How to improve your sleep
B. How important enough sleep is!
C. How amazing if you look good!
D. How to avoid trouble of seeing
1.C
【解析】细节理解题。根据文章第三段最后一句“…infection-fighting antibodies(抗体) are reduced …when you don’t get enough sleep.”如果你没有得到充足的睡眠，抗体就会被减少，可知，充足的睡眠对抗体有益，故选C。
2.A
【解析】细节理解题。根据文章第四段“Watson says his study shows that the immune system works best when the body gets enough sleep Watson说他的研究表示，刚身体得到充足的睡眠，免疫系统就会工作得很好”，可知，充足的睡眠对自身免疫系统有好处，故选A。
3.D
【解析】综合判断题。根据文章最后“Signs you may not be getting enough sleep 你没有得到充足睡眠的信号”中的第三条“You have trouble remembering things 记忆困难”可知，当你的记忆越来越差，可能是因为睡眠不足，故选D。
4.A
【解析】推理判断题。文中已经说明了睡眠充足的重要性，故B选项错误；C、D两项是文章最后一段最后两条的眼神，故排除C、D两项；文章最后描述了一些人正受睡眠问题的困扰，所以接下来应是就如何改善睡眠进行探讨。故选A。
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