Research Review: Long Working Hours – The Leading Cause of Death in Workers

In this article, our expert Dr Nick Chartres – Director, Science & Policy, Program on Reproductive Health and the Environment, at the University of  California San Francisco – reviews new research by The World Health Organization (WHO) and the International Labour Organization (ILO) on the impact of long working hours, and breaks it down to give us the vital parts we need to know. 



Preventing exposures to occupational risk factors, such as long working hours is critical to the health and safety of workers and should be a priority of governments and the private sector. 

The World Health Organization (WHO) and the International Labour Organization (ILO) are developing joint estimates (WHO/ILO Joint Estimates) of the work-related burden of disease and injury for ten different exposures and outcomes (e.g. long working hours and stroke). 

What did the study measure?

The first step of developing these estimates involved conducting systematic reviews (think gold standard reviews) of ALL of the evidence examining the relationship (level of risk) between working hours (a standard, 35-40 hours/week and long, three categories: 41–48, 49–54 and ≥55 h/week) and risk of heart disease and stroke. 

They then calculated the exposed global population by modelling data from more than 2300 surveys collected in 154 countries from 1970-2018. 

Finally they calculated the population-attributable fractions from estimates of the population exposed to long working hours with the risks on the diseases from the systematic reviews. 

What did the study find?

  • A 17% increase in risk of heart disease and a 35% increase in risk of stroke from working more than 55 hours/week when compared to a 35-40 hours/(standard) week.
  • About 9% of the world’s population works more than 55 hours/week.
  • 745,000 deaths from stroke and ischemic heart disease were attributed to long working hours.
  • 72% of deaths occurred among males.
  • Most deaths recorded were among people dying aged 60-79 years, who had worked for > 55 hours/week between the ages of 45-74 years.
  • People living in the Western Pacific (China, South Korea, Australia and Japan among other countries) and Southeast Asia regions were most at risk.

How much weight should we give this research?

A LOT. This is the most rigorous evaluation of the evidence on this topic and cutting edge scientific methods were used to develop the Joint Estimates.

What’s the key takeaway from this research?

With approximately 9% of the world’s population working more than 55 hours/week it makes long working hours the occupational risk factor with the largest estimated burden. Long working hours are killing more people than cancer.

What does this mean for your work/research/industry? 

Governments must introduce and enforce maximum limits on working time. Working hours must become more flexible. The private sector must take collective action to protect the health of its workers.