Working Overtime Wears on the Heart

Working more than 40 hours a week may lead to heart problems.

Working long hours may increase the risk of developing coronary heart disease (CHD), according to the results of a Korean study.

While previous research has shown that working overtime is linked with poor health outcomes, the current study, published online in the American Journal of Industrial Medicine, analyzed the relationship between working long hours and CHD risk among Korean adults. The analysis enrolled 8350 participants aged 19 years and older from the Korean National Health and Nutrition Examination Survey IV (2007 to 2009) who answered questions about their work life and health status, in addition to completing physical examinations.

The participants worked an average of 50.1 hours per week, though 38% worked more than 52 hours. The results indicated that risk factors for CHD, including blood pressure, cholesterol levels, diabetes, and smoking habits, were significantly related to increased working hours. Nonetheless, those who worked less than 30 hours a week had the highest blood pressure and cholesterol levels across the entire study population.

When compared with those who worked 31 to 40 hours a week, participants who worked more than 40 hours had a significantly increased 10-year risk for CHD. In addition, the results indicated a dose-response relationship, meaning the more hours an individual worked, the higher the risk for developing CHD.

The 10-year risk for CHD increased by 42% among those who worked 61 to 70 hours per week, 63% among those who worked 71 to 80 hours, and 94% among those who worked more than 80 hours. Those who worked fewer than 30 hours a week, however, had a higher risk than those who worked 31 to 40 hours.

“Health limitations as well as advantages may have influenced how much people worked,” the study authors explained. “Persons who have worse cardiac health may not work long hours.”

The results also indicated that the relationship between overtime and 10-year CHD risk was stronger among women than men. As working hours increased, the risk increased 4.65-fold among women, compared with a 1.47-fold increase in risk among men. The authors suggested that this difference might represent women’s additional domestic duties and burden.

In addition, overall risk for CHD was higher among manual workers; however, the association between working hours and risk was stronger among non-manual workers.

“We hope that these findings contribute to the proper management of working conditions and enhance quality of health care for workers, particularly for those at risk for [CHD],” the authors concluded.