New research finds that employees who work 46 hours or more per week over a period of 10 years have a greater risk of experiencing some type of cardiovascular disease (CVD) event than those working 45 hours or less.

Sadie H. Conway, Ph.D., of the University of Texas Health Sciences Center, Houston, and her colleagues analyzed the relationship between work hours and CVD using data on more than 1,900 participants from a long-term follow-up study of work and health. All participants had been employed for at least 10 years. During the study, a physician-diagnosed CVD event – angina, coronary heart disease or heart failure, heart attack, high blood pressure, or stroke – occurred in about 43 percent of participants.

“This study provides specific evidence on long work hours and an increase the risk of CVD, thereby providing a foundation for CVD prevention efforts focused on work schedule practices, which may reduce the risk of CVD for millions of working Americans,” said Conway.

The study, published in the March Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine (ACOEM), found that the risk of CVD events increased by one percent for each additional hour worked per week over at least 10 years, after adjustment for age, sex, racial/ethnic group and pay status. The difference was significant only for full-time workers, not part-timers.

"In general, we found that the risk of CVD increased as the average weekly working hours increased," wrote Conway and the other researchers. They noted that among full-time workers, CVD risk appears lowest between 40 and 45 hours per week.

While previous research suggested increased CVD risk with longer working hours, the new study is the first to show a “dose-response” effect.