Last Thursday was World Stroke Day. Did you notice? Or were you too busy working long hours to pay any attention? If so, take note of this: A recent study found long working hours may boost stroke risk.
Several studies have observed a correlation between long working hours or work-induced stress and adverse health effects, including heart disease, diabetes and substance abuse disorders, among others. One recent study even sought to show how many years work stress lopped off life expectancy.
In a report published in the Oct. 31 issue of the Lancet (PDF), a team of public health researchers from several European institutions found that long working hours significantly increased the risk of stroke and slightly increased the risk of coronary heart disease, adding to the list of damaging effects work can have on health.
The researchers conducted a meta-analysis of 25 published and unpublished studies of 24 cohorts in Australia, Europe, Israel and the U.S. involving over 600,000 individuals who were healthy at the start of the studies. All 25 studies were included in the meta-analysis of heart disease, while the stroke meta-analysis included 17 of the studies. Standard hours were defined as 35 to 40 hours per week and long work hours were defined as 45 hours or more per week in some studies and 55 hours or more in others.
After controlling for age, sex and socio-economic status, the study authors found that people working 55 or more hours per week had a 13% higher risk of coronary heart disease than those who worked a standard week. The effect for stroke was more dramatic: the risk was 10% higher for those working 41-48 hours, 27% higher for 49-54 hours, and 33% higher for 55 hours or more worked per week.
The findings are significant not just because of the demonstrable impact of working hours on stroke risk but because of the size of the cohort studied. “Combining estimates from published studies and unpublished data allowed us to examine the status of long working hours as a risk factor for coronary heart disease and stroke with greater precision and a more comprehensive evidence base than has previously been possible,” wrote lead author Mika Kivimäki, a University College London epidemiologist.
Highlighting the public health implications of the findings in an accompanying comment, Dr. Urban Janlert of the University of Umea in Sweden notes that long working hours are not uncommon globally, even in the European Union, which has legal protections in place allowing workers to cap working hours at 48 per week. In the U.S., where no such protections exist, a Gallup poll pegged the average full-time employee clocking in at nearly 47 hours per week; salaried employees, exempt from receiving overtime pay, said they averaged 49 hours per week. Half of salaried American employees reported working 50 or more hours per week. “That the length of a working day is an important determinant mainly for stroke, but perhaps also for coronary heart disease, is an important finding,” Janlert wrote.
"Working conditions are important determinants of people's health," Janlert noted. "Essentially, if long working hours present a danger to health, it should be possible to change them."
Janlert suggests researchers could test the study results by assigning some workers with long hours to reduced schedules and tracking the results. Though a few companies are testing the benefits of shorter working hours, there's little evidence employers are inclined to move in that direction on a broad scale. Even though longer hours show declining productivity after a certain point, workers worldwide are reporting longer hours and greater pressure to put in additional hours outside of work.
But with evidence mounting that work hours and stress can have such a significant impact on health, perhaps it is time, as Janlert notes, to make it "the subject of general policy discussions."