WHO Study Finds Long Working Hours May Increase Risk of Stroke, Heart Disease Mortality

Exposure to long working hours may increase risk of ischemic heart disease (IHD)- and stroke-related death and disability, according to study findings published this week in Environment International.

Although several countries categorize conventional and overtime work differently, researchers say that occupational epidemiologists have often cited long working hours as belonging to 3 analytical categories: 41 to 48 hours, 49 to 54 hours, and 55 or more hours per week.

Notably, prior systematic reviews and meta-analyses conducted by the World Health Organization (WHO) and the International Labour Organization (ILO) comparing standard working hours of 35 to 40 hours per week with these 3 overwork time frames on relative risk of IHD and stroke indicated that those working 55 or more hours per week were at higher risk for both conditions.

“Evidence from previous studies suggests working long hours can increase mortality and morbidity from ischemic heart disease and stroke through psychosocial stress,” added the study authors.

With working time predicted to increase for some industries amid the introduction of new information and communication technologies, both organizations sought to further quantify the impact of exposure to long working hours and attributable burden of disease globally.

They created the WHO and ILO Joint Estimates of the Work-related Burden of Disease and Injury (WHO/ILO Joint Estimates), which provided estimates of global, regional, and national exposure to long working hours of 55 or greater hours per week for 194 countries and the burdens of IHD and stroke attributable to these estimates for 183 countries, by sex and age, for 2000, 2010, and 2016.

Based on prior findings of the systematic reviews, they calculated population-attributable fractions from estimates of the population exposed to long working hours and relative risks of exposure to the diseases.

“The exposed population was modeled using data from 2324 cross-sectional surveys and 1742 quarterly survey datasets,” explained researchers. “Attributable disease burdens were estimated by applying the population-attributable fractions to WHO’s Global Health Estimates of total disease burdens.”

Of the global population in 2016, 488 million people (95% uncertainty range [UR], 472–503 million) or 8.9% were estimated to have worked 55 or more hours per week, with men and adults of early middle-age more commonly exposed. Moreover, global prevalence of long working hours exposure increased by 9.3% (UR, 4.3%-14.6%) between 2000 and 2016.

Among those exposed, an estimated 745,194 (UR, 705,786-784,601) deaths and 23.3 million (UR, 22.2-24.4 million) disability-adjusted life-years (DALYs) attributable to IHD and stroke combined were found. “This was roughly equal between the 2 causes, with IHD and stroke accounting for 46.5% and 53.5% of estimated deaths.”

Compared with employees working standard working hours, those working 55 or greater hours were associated with a 35% higher risk of stroke (relative risk [RR], 1.35; 95% CI, 1.13-1.61) and 17% higher risk of dying from IHD (RR, 1.17; 95% CI, 1.05-1.31).

Furthermore, the population-attributable fractions for deaths were 3.7% for IHD and 6.9% for stroke, whereas those for DALYs were 5.3% and 9.3%, respectively.

"Teleworking has become the norm in many industries, often blurring the boundaries between home and work. In addition, 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,” said Tedros Adhanom Ghebreyesus, WHO Director-General, in a statement.

“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.”

Reference

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. Environ Int. Published online May 17, 2021. doi:10.1016/j.envint.2021.106595