Did you sleep the day away on March 21? Well， you should have done that because it was World Sleeping Day. This is the one day of the year when people around the world care about their sleep and ask themselves a lot of questions about sleep.
Why do we need sleep? Nobody as yet can give a correct answer to this question. However， tests have shown that lack of sleep over about four weeks leads to a strong drop in body temperature， great weight loss and finally sickness.
Different people need different amounts of sleep. Eight hours a night is considered the average amount of sleep. For teenagers the least number of sleeping hours advised by doctors are ten hours for primary school students， nine for junior highs and eight for senior highs.
Some people seem to get along just fine with very little sleep at night. Leading American scientist Thomas Edison said that sleep was a waste of time. He did， however， take naps during the day. On the other hand， Albert Einstein， another great scientist， said he needed at least ten hours' sleep a night.
Here are some of the most useful suggestions， for a good night's sleep.
Go to bed regularly.
Use your bed only to sleep
. Don't exercise in the evening.
Keep the bedroom dark and quiet.
Drink a glass of milk before sleep.
