Pan Jie, an auditor working for PwC in Shanghai, dies of fever-induced complications due to overwork on April 10, 2011, at the age of 25 (LIU YING)

Guomao, a bustling area in Beijing's Central Business District where Ning worked, is a gathering place for taxi drivers after 10 p.m. as they all know people working for companies there often stay late, so it is easy to get passengers.

"We get trapped at work," said 30-year-old Jin Jian, who worked for an advertisement company at Jianwai Soho community in Guomao. "The whole advertisement industry means endless working anyway and we cannot live in this city without salaries since the living cost in Beijing is rocketing."

Jin used to be satisfied with his salary, which is more than 10,000 yuan ($1,630) a month, but is still not enough for him. "My mortgage is about 6,000 yuan ($978) a month and basic living costs are about 3,000 ($489)," said Jin. "If I get married and have a baby, this salary is far from enough."

It is not only young professionals who feel under pressure. The first generation of white-collar workers in China, mostly in their 40s or 50s, is also in an awkward situation.

David, who declined to reveal his Chinese name, has been working for foreign-funded companies for 20 years and lives a stable middle-class life as a marketing director of the Asian-Pacific region.

In January 2013, the financial report of the company said that some employees would need to be cut due to the slowing economy.

"Foreign companies are no longer glorified places to work, as state-owned and private companies in China are improving very fast with the development of the economy," said David. Some of his contemporaries have started their own businesses with some success, but his opportunity for such entrepreneurship has passed.

"My wife is a housewife and I have two kids studying at an international school," said David. As the only bread winner in the family, he doesn't want to take risks.

Money vs. health

On May 13, 24-year-old Li Yuan died of a sudden heart attack at the Beijing office of Ogilvy & Mather after working overtime for a month prior to his death.

The final message Yuan posted on the Chinese social media site Weibo.com shows a photo of the young ad man saluting the camera, presumably as he left the office for the day.

Two days later, a young IT employee working at 17173.com, a Web game operator in Fuzhou City, capital of Fujian Province, died of viral myocarditis due to overwork.

Karoshi, the Japanese term for death by overwork, used to happen mostly in manufacturing factories or construction sites, but is more frequently claiming the lives of people in white collar professions in China. According to a report on China Youth Daily, almost 600,000 people die of work exhaustion in China each year.

According to a survey conducted by the China Moderate Labor Study Center, founded in September 2012, about 70 percent of the white collar employees working in the Central Business District of Beijing show signs of overwork and 38.4 percent are under serious pressure.

"Things are highly competitive nowadays and some workers have to work overtime to compete with their counterparts," said Yang Heqing, director of the center.

Since 1995, China has adopted a standard work week of 40 hours. "But sometimes it is the employees who want to work extra hours, so it is hard to control," said Yang. "It has become a common phenomenon that working long hours is seen as proof of working hard, while it is not the time spent working that matters, but the quality."

"We believe that work always comes before life, which also contributes to the stress of working," said Peng Guanghua, a professor at Beijing-based Renmin University of China. "It is a topic for both employers and employees, and the research also shows that working overtime can sometimes lower productivity instead of improving it," he said.