We spend about one-third of our lives asleep．This may sould like a lot of time，but it is not wasted．Our bodies need sleep to stay healthy．Not getting enough aleep can make us sick．
Sleep and our immune（免疫）system
The immune system protects the body fro
m 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 im
portant 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 w
ork 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 ho
urs 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
答案
1C 2A 3D 4A
dness?
ing hall. 
ng men