According to the combined study by the UN's World Health Organization and International Labor Organization, working more than 55 hours a week increases the risk of death from heart disease and stroke.
As the Covid-19 pandemic accelerates workplace changes that could reinforce the tendency to work longer hours, the WHO-ILO study is the first global analysis of the risks to life and health associated with working long hours.
It does not focus on the pandemic but on the preceding years and the data has been synthesized from dozens of studies involving hundreds of thousands of participants.
"Working 55 hours or more per week is a serious health hazard," said Maria Neira, director of the WHO's environment, climate change and health department.
"It's time that we all -- governments, employers, and employees -- wake up to the fact that long working hours can lead to premature death."
The Risks Involved
Most of the recorded deaths were among people aged 60 to 79, who had worked 55 hours or more per week when they were between 45 and 74 years old.
The study concluded that working 55 hours or more per week was associated with an estimated 35-percent increase in the risk of suffering a stroke, and a 17-percent rise in the risk of dying from ischemic heart disease, compared to working 35 to 40 hours.
"With working long hours now known to be responsible for about one-third of the total estimated work-related burden of disease, it is established as the risk factor with the largest occupational disease burden," the WHO said.
The organization also said that the coronavirus crisis was speeding up developments that could feed the trend towards increased working time for the professionals.