This 31-year-old Japanese journalist died holding a phone after working 159 hours of overtime in a month

ANN News/YouTube

A political journalist in Japan died from overwork, her employer has revealed four years after her death.

Miwa Sado died of congestive heart failure in 2013 after working 159 hours and 37 minutes of overtime in one month, her employer, the Japanese national broadcaster NHK, announced on Wednesday, according to the Asahi newspaper. That's an average of about 5.9 hours of overtime a day, including weekends.

According to a local labour office in Tokyo, the reporter's cause of death was "karoshi" — a Japanese word that literally means "death from overwork."

The 31-year-old had been covering two elections — one regional, one national — in the month leading up to her death on July 24, 2013. She was found collapsed in her bed, holding a mobile phone, Asahi said.

A month before her death, Sado had emailed her father: "I am too busy and stressed out and think about quitting my job at least once a day, but I guess I have to hang on."

NHK said it waited four years before disclosing Sado's cause of death because her parents originally wanted it to be kept private. They changed their mind this summer, the national broadcaster told Asahi.

Sean Pavone

According to Japanese law, the typical employee can only work 40 hours a week, or no more than eight hours a day, with up to an hour's break.

Japan is currently planning to cap overtime at 100 hours a month, which some critics said was still excessive, according to Japanese newspaper Kyodo.

The government published a survey last October saying that more than one in five companies had employees who worked more than 80 hours of overtime a month — about four hours of overtime a day, excluding weekends. The paper also noted that 2,159 people committed suicide in 2015 due to work issues.

Last December, 24-year-old Matsuri Takahashi jumped to her death from her dormitory after reportedly logging 105 overtime hours within a month.