Sleep is like food for the brain. Enough sleep helps the body and the brain grow and develop. However,many Chinese do not sleep well,and many do not pay enough attention to sleep. The Chinese Medical Doctor Association released the 2013 China Sleep Quality Index on March 19 to mark World Sleep Day---March 21. According to the index,nearly a quarter of Chinese people don't  sleep well.Half said that they feel tired after getting up and 15 percent people have trouble falling asleep. Ye Jingying,a sleep expert at Beijing Tongren hospital,says:"If people often wake up during the night,or always feel weak and tired in the day,they should pay attention to their sleep pattern." Many people play with their cell phones or i pads before sleeping.The report said that this is one of the main reasons for bad sleep.Other reasons include stress and bad moods. How to sleep well? Above all,get enough sleep.Seven to nine hours of sleep every night is perfect for an adult,and eight to nine hours is best for a teenager. Forming good sleep habits is important.The report suggested that people need to keep away from digital devices for at least an hour before sleep. The lights keep their brains excited for a long while.Other suggestions include:try to go to sleep and wake up at the same time every day,even on weekends and during holidays,and do the same relaxing things before bed each night,like listening to soft music. From the article,Which of the following may NOT cause sleeping problems?
Having sad or angry feelings. Reading a book late at night. Playing with digital devices before sleeping. Being under strong stress about their life or work.