We all need it, but for many it's a nuisance that they feel deprives them of living, Zhang Lei reports.

For night owls like Chen Danhong, 28, who works for a technology company in Beijing, the day really just begins after about 8 pm, a psychological hint that she can relax, she says.

"When I get home I'm feeling worn out and tired, but that suddenly turns to excitement and I go on the internet, read novels or watch movies. I'll be playing video games and continually saying to myself, "OK, this is the last one" before I eventually realize that it's 2 o'clock. It's the same with watching TV, bingeing on a whole series before I realize it's 4 o'clock."

For Chen, breaking promises about getting enough sleep has become a way of life. "I know that if things go on like this it's going to take a toll on my health, but I just can't help myself."

Chen is suffering from what is called unforced sleeplessness, a term borrowed from tennis, in which an unforced error refers to a mistake that occurs when there is no pressure.

Common symptoms include falling asleep later than 2 am, with the average time taken to fall asleep being more than one hour. Young people in cities are most vulnerable to such symptoms, according to the 2020 Chinese National Healthy Sleep White Paper by the China Sleep Research Association. Common causes are loneliness, overtime sequelae, excessive stress and emotional disorders.

Nearly 75 percent of respondents to a survey said they had sleep problems, the paper says. The incidence of insomnia among Chinese adults is as high as 38.2 percent, which means that more than 300 million Chinese have sleep disorders. The most common of these are insomnia and obstructive sleep apnea syndrome.

The Sleeping Obsessive-Compulsive Disorder Group on the social media site Douban, founded in 2006, says it has more than 100,000 members. Words you will often hear members of the group using include procrastination, anxiety and escapism.

"I really can't do anything about going to bed early," one member said in a posting.

On March 21, designated by the United Nations as World Sleep Day, Nanguo Morning News, a newspaper in Guangxi autonomous region, conducted a survey that attracted 2,000 respondents, Forty-three percent of them said they sleep late every day because they feel that the only time of the day that truly belongs to them is just before they go to bed, and they treasure that so much that they are reluctant to sleep.

About 36 percent of respondents said they go to bed late at least three days a week, and only 2 percent said they never go to bed late. According to the survey, the reasons for going to bed late vary widely, with overtime work or taking care of a baby accounting for just 5 percent of the respondents' answers on this question. Sixty-four percent said they sleep late because they watch dramas, variety shows, read books or play with their mobile phones. Fourteen percent said they do not want to go to bed too early even if they have nothing to do.

Twenty-six percent said their time during the day has been occupied by work and children, and they want to enjoy the time that truly belongs to them; 25 percent said they are very sleepy and tired in the middle of the night, but their minds are very active; 21 percent said a hindrance to sleep is their mobile phone, while at the same time doing things with them makes them happy as they retired for the night.