The study concludes that working 55 or more hours per week is associated with an estimated 35 per cent higher risk of a stroke and a 17 per cent higher risk of dying from ischemic heart disease, compared to working 35-40 hours a week.
Further, the number of people working long hours is increasing, and currently stands at 9 per cent of the total population globally.
This trend puts even more people at risk of work-related disability and early death.
The new analysis comes as the Covid-19 pandemic shines a spotlight on managing working hours; the pandemic is accelerating developments that could feed the trend towards increased working time.
"The Covid-19 pandemic has significantly changed the way many people work," said Tedros Adhanom Ghebreyesus, WHO director-general.
He said teleworking has become the norm in many industries, often blurring the boundaries between home and work.
In addition, he said many businesses have been forced to scale back or shut down operations to save money, and people who are still on the payroll end up working longer hours.
"No job is worth the risk of stroke or heart disease. Governments, employers and workers need to work together to agree on limits to protect the health of workers," said the WHO DG.
"Working 55 hours or more per week is a serious health hazard," added Maria Neira, director of Department of Environment, Climate Change and Health at the World Health Organization.
"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 WHO and ILO said Governments, employers and workers can take the following actions to protect workers' health:
Governments can introduce, implement and enforce laws, regulations and policies that ban mandatory overtime and ensure maximum limits on working time; bipartite or collective bargaining agreements between employers and workers' associations can arrange working time to be more flexible, while at the same time agreeing on a maximum number of working hours; and employees could share working hours to ensure that numbers of hours worked do not climb above 55 or more per week.
Two systematic reviews and meta-analyses of the latest evidence were conducted for this study.
Data from 37 studies on ischemic heart disease covering more than 768,000 participants and 22 studies on stroke covering more than 839,000 participants were synthesized.
The study covered global, regional and national levels, and was based on data from more than 2,300 surveys collected in 154 countries from 1970-2018.