Nearly 60 percent of primary and middle school students in Shanghai are nearsighted, Shanghai Evening Post reported on Wednesday.

Among senior high students, 86 percent are shortsighted, and the numbers are 70 percent and 38 percent among students at junior high and elementary schools, the paper said, citing a survey conducted by the Shanghai Municipal Center for Disease Control and Prevention in 2010.

Excessive schoolwork and frequent contact with electronic screens were the main causes for the high incidence of myopia among teenagers, the report said.

The increase in myopia occurs during the transition periods between schools, as the number of nearsighted students grew more than 10 percent from the third year of junior high to the first year of senior high, the report said.

The survey also found that middle school students in Shanghai spend 2.8 hours a day using electronic products with screens, and four hours on weekends, which is much longer than the suggested two hours by the American Academy of Pediatrics, said the report.