Paragraph 1
Sleep is essential for human life. We can actually live longer without food than without sleep.
Most people spend about a third of their life sleeping. That means during our life we will spend
about twenty-five years asleep. While the average person sleeps about seven hours a night, some
people can manage with as little as four hours. We don’t all need the same amount of sleep.
Paragraph 2
So what happens when we are asleep? There are five stages in a cycle of sleep. Each cycle
lasts about 90 minutes and we often repeat this cycle five times a night. In the first two stages,
we fall into a light sleep. In stages three and four, we are in a deep sleep and our heart rate
and breathing slows down. In stage five, our brain becomes active and our eyes move around
quickly. This stage of sleep is called REM, which stands for rapid eye movement. It is during
REM sleep that we do all our dreaming.
Paragraph 3
We all know that sleep is good for us, but what are the benefits? One benefit is that it helps us
to resist illness. Without enough sleep, our body cannot fight off colds and the flu as easily. Your
sleep pattern can also affect your diet. Researchers at the University of Chicago discovered that
poor sleep increased a hormone in the body that makes us hungry. This means that people who
sleep badly often eat more high calorie foods and gain more weight.
Paragraph 4
Sleep also plays a part in our performance at school and at work. A number of reports have
shown that children who get a good night’s sleep do better in school. Obviously, one reason for
this is that if you are very tired you cannot focus. However, there is another important reason.
Scientists believe that sleep is important for our memory. While we are asleep our brain deals
with information we have learnt and sleep helps strengthen our memories.
Paragraph 5
Another essential part of sleep to understand is our circadian rhythm, or ‘body clock’. This
is our body’s natural rhythm of sleep. Generally, our body clock tells us to sleep when it is
dark and wake when it is light. However, studies now suggest that young people’s body clocks
change when they become teenagers. Some scientists believe that teenagers are not lazy, but
biologically programmed to go to bed later and wake up later.
ISE I
Turn over page page 3
Questions 1–5
The text on page 2 has five paragraphs (1–5). Choose the best title for each paragraph from A–F
below and write the letter (A–F) on the lines below. There is one title you don’t need.
1. Paragraph 1
2. Paragraph 2
3. Paragraph 3
4. Paragraph 4
5. Paragraph 5
A The reason we dream
B Changes in sleep routine
C Sleep and learning
D How much we sleep
E Different types of sleep
F Sleep and good health 

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