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The more overtime hours worked, the greater the risk for heart disease, study finds

The findings add to a growing body of evidence that suggests long workweeks are bad for our health — including our mental health.

The more hours we work each week — once we’ve passed a threshold of 45 hours  — the greater our risk of developing cardiovascular disease, according to a new study from researchers at the University of Texas.

In fact, say the researchers, it may be time to start including working more than 45 work hours per week as an independent risk factor for cardiovascular disease. 

That’s a troubling finding, given that adults employed full time in the U.S. work an average of 47 hours a week, according to a 2014 Gallup poll. Many have jobs that demand even more of their time. In that same poll, 40 percent of the respondents said they worked for at least 50 hours — and 18 percent said they worked for a grueling 60 hours or more — during a typical week.

The finding is also worrying because cardiovascular disease, which includes high blood pressure, angina, coronary heart disease, heart attack and stroke, is the leading cause of death in both men and women in the U.S., claiming about 610,000 Americans each year, according to the Centers for Disease Control and Prevention (CDC).

A risky business

Previous research has linked long workweeks with an increased risk of cardiovascular disease. Indeed, as I reported in Second Opinion last August, a large meta-analysis found that working 55 hours or more per week is associated with a 33 percent increased risk in having a stroke and a 13 percent increased risk of developing coronary heart disease.

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This new study, however, is the first to report a “dose-response” relationship between work hours and cardiovascular disease: The longer the workweek, the greater the risk.

The University of Texas researchers came to this conclusion after analyzing data collected over a period of 25 years (1986 through 2011) from 1,926 men and women who were participating in long-term study that tracked their health and work hours. Most of the participants were white (89 percent) and employed in service industries (70 percent). Most also had non-manual jobs (73 percent). Their average age at the start of the study was 33 years.

None of the participants had diagnosed heart disease in 1986, but 822 (43 percent) had developed it by 2011. When the researchers compared the working hours of those who developed cardiovascular disease with those who didn’t, they found that once workers started putting in more than 45 hours a week on their job, their risk of cardiovascular disease became progressively greater. 

People who worked 55 hours per week for 10 years or more, for example, were 16 percent more likely to develop heart disease than those who worked 45 hours. That risk was 35 percent greater for those who worked 60 hours and 52 percent higher for those who worked 65 hours.

And for people who worked more than 75 hours per week, the risk doubled.

These relative risks were determined after adjusting for age, gender, race/ethnicity, and income — all factors that can separately influence the likelihood of developing cardiovascular disease.

Only a correlation

This study has several limitations. It’s an observational study, which means it can show only a correlation between longer working hours and an increased risk of cardiovascular disease, not a cause and effect. Also, the study’s participants were overwhelmingly white and in non-manual jobs, so it’s not known if other populations would have similar results. In addition, participants provided their own accounts of their weekly work schedule — accounts that may or may not have been accurate. 

Still, the findings add to a growing body of evidence that suggests long workweeks are bad for our health — including our mental health. And they suggest that public health efforts aimed at reducing cardiovascular disease in the U.S. may need to focus on work schedule practices, say the study’s authors.

Unfortunately, however, the researchers offer no specifics on how to go about doing that. In the meantime, U.S. workers not only work longer hours than their counterparts in other developed countries, but also remain the only workers in the developed world without any kind of mandatory paid leave.

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FMI: The study was published in the Journal of Occupational and Environmental Medicine, and can be downloaded in full from the publication’s website.