Lack of sleep among children and teenagers in China has worsened in the past decade, with more than 80 percent getting insufficient sleep on school days, a report released on Monday said.

Chinese youngsters snoozed an average of 7.8 hours a night on school days last year, 20 minutes less than in 2009, according to the report from the Chinese Academy of Sciences' Institute of Psychology.

Researchers surveyed more than 15,800 students from Henan, Hebei and Guangdong provinces from April to July, asking them what time they went to bed and woke up on days when they went to school.

Only 46.4 percent slept for at least 8 hours, compared with 47.4 percent in 2009, the report said.

According to an action plan laying out measures to be taken from 2019 to 2030 to promote the health of citizens, primary school students are recommended to get a minimum of 10 hours' sleep a night. Nine hours is recommended for junior high school students and 8 hours for senior high school students.

By those standards, more than 95 percent of students in primary schools, nearly 91 percent of those in junior high schools and 84 percent of students in senior high schools do not get enough sleep on school days, heightening the risk of them developing cognitive, mental and physical health problems, the report said.

Hou Jinqin, a researcher at the National Institute of Education Sciences who co-authored the report, said local authorities should implement measures suggested by the Ministry of Education, such as lessening academic burdens, postponing start times at school and encouraging children to enroll at institutions closer to home so they can have more sleep.

In terms of the COVID-19 epidemic's impact on sleep, she said research overseas had shown that school closures forced by the epidemic had given young students studying at home an extra two hours of sleep a night.

In China some studies had revealed no marked differences in sleeping patterns of students before and after schools reopened, she added.