But researchers conducting the largest study thus far of the relationship between working hours and cardiovascular health have shed light on just how bad working overtime really is for your heart.
After collecting data on over 600,000 people from the U.S., Europe, and Australia, researchers reported Wednesday that people who work 55 hours or more per week have a 33 percent greater risk of stroke and a 13 percent greater risk of coronary heart disease than those working standard hours (between 35 and 40 hours per week.)
Researchers told the New York Times they expected to find the connection between long hours and heart attacks, but were “surprised’’ at the heightened risk of stroke.
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The report’s authors combined results from multiple studies, published and unpublished, trying to account for any factors that could skew results, like sex, age, and socioeconomic status. Their analysis did not draw conclusions about what caused the increased risk and did not account for all potentially relevant factors.
Dr. Mika Kivimaki, a professor of epidemiology at the University College London and his colleagues tracked 528,908 men and women (from the pool of over 600,000 people) for 7.2 years and recorded who had a stroke. The researchers controlled for smoking, physical activity, high blood pressure, and cholesterol. They found that the longer hours the employee worked, the more likely he or she was to have a stroke.
In their analysis of coronary heart disease, they studied 603,838 people (some also used in the stroke analysis) for 8.5 years, tracking who received diagnoses for heart disease. They found a weaker link between working overtime and heart disease.
Some doctors do not approve of their methodology, with Dr. Steven Nissen, the chief of cardiovascular medicine at the Cleveland Clinic calling the results “unconvincing.’’ Others pointed out the study’s failure to account for participants’ family history, sleep patterns, and job strain (careers with high demand and low control), suggesting a randomized trial as a better method to link working long hours to strokes.
Even if the risk for individuals is slight, if supported, the findings are noteworthy for large populations of people working over 35 and 40 hours per week. And recent surveys show that quite a few Americans are doing just that.
Gallup surveys from 2013 and 2014 reported nearly four in 10 full-time Americans worked at least 50 hours per week.