Estimated Disease Burden from Long Work Hours

In May of 2021, the World Health Organization (WHO) and International Labour Organization (ILO) presented the first joint estimate of the burden of work-related disease and injury. The report, published in Environment International, draws on data from 194 countries from 2000 to 2016 and finds that there are higher risks of ischemic heart disease and stroke among people who work long hours (55 hours per week or more) when compared to those who work 35-40 hours per week.

WHO/ILO estimates that over 745,000 deaths and 23.3 million disability-adjusted life years (DALYs) are attributable to ischemic heart disease and stroke. These findings are calculated using models called population attributable fractions (PAFs), which quantify the proportion of death or disease that is driven by a specific risk factor, such as overwork, based on extensive systematic reviews. Stroke was found to have a higher PAF than heart disease, with 6.9 percent of stroke deaths and 9.3 percent of stroke DALYs attributable to overwork, compared to 3.7 percent of heart disease deaths and 5.3 percent of heart disease DALYs.¹

The disease burdens attributed to overwork are greater than those attributed to many other occupational hazards. The Global Burden of Disease (GBD) 2016 study found that 1.53 million deaths were attributable to a total of seven different risk factors (carcinogens; asthmagens; particulate matter, gases and fumes; secondhand smoke; noise; ergonomic risk factors for low back pain; and risk factors for injury). Notably, the study reported an overall reduction of deaths and DALYs since 1990, indicating that occupational exposures are controllable and that their proper regulation can prevent disease and death.²

But while exposure to some occupational hazards may be decreasing, between 2010 and 2016, the proportion of the population working long hours increased substantially — by 9.3 percent — according to the WHO/ILO report. This means that, based on the study’s models, deaths from ischemic heart disease and stroke increased by 41.5 percent and 19.0 percent, respectively. Those most affected include older men: nearly three-quarters of deaths occurred among males, and most of the deaths were recorded among people aged 60-79 years who had worked for 55 hours or more per week between the ages of 45 and 74 years. People living in the Western Pacific and Southeast Asia regions were also among those most likely to work long hours;³ in the U.S., less than 5 percent of the population works long hours.¹

Notably, there has been some criticism of the WHO/ILO’s methodology, with authors of similar studies noting that the results are not supported by other published data reviews, and that subgroup analyses reveal greater complexity in patterns. In particular, Kivimäki et al. note that “findings of socioeconomic interaction suggest that at this stage the conclusion should be restricted to low socioeconomic status occupations only,” in response to a paper published in 2020 analyzing the effect of long working hours on ischemic heart disease.⁴ That is, the authors suggest that it is not only the length of working hours that impact health, but also the nature of the work being conducted. The WHO/ILO report concedes that more research must be done on a global scale to assess this hypothesis.¹

The health consequences created by an overworked population is a subject that deserves increased scrutiny moving forward. Other scholars have suggested that economic recessions such as the 2008 global financial crisis can drive increases in working hours, as might the expansion of the gig economy and new working-time arrangements that include remote work. The WHO/ILO report only includes data from before the COVID-19 pandemic, and more research analyzing how this public health crisis continues to impact working conditions is warranted.

References 

1. Pega F, Náfrádi B, Momen NC, et al. Global, regional, and national burdens of ischemic heart disease and stroke attributable to exposure to long working hours for 194 countries, 2000–2016: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Environ Int. 2021;(106595):106595. 

2. GBD 2016 Occupational Risk Factors Collaborators. Global and regional burden of disease and injury in 2016 arising from occupational exposures: a systematic analysis for the Global Burden of Disease Study 2016. Occup Environ Med. 2020;77(3):133-141. 

3. Long working hours increasing deaths from heart disease and stroke: WHO, ILO. World Health Organization. https://www.who.int/news/item/17-05-2021-long-working-hours-increasing-deaths-from-heart-disease-and-stroke-who-ilo 

4. Kivimäki M, Virtanen M, Nyberg ST, Batty GD. The WHO/ILO report on long working hours and ischaemic heart disease – Conclusions are not supported by the evidence. Environ Int. 2020;144(106048):106048.