UTHealth study: Long work hours linked to higher cardiovascular disease risk

Sadie H. Conway, Ph.D.

HOUSTON – (March 23, 2016) – Working long hours, particularly averaging 46 hours or more per week for many years, may increase the long-term risk of cardiovascular disease (CVD), according to researchers at The University of Texas Health Science Center at Houston (UTHealth). Study results were published this month in the Journal of Occupational and Environmental Medicine.

"In general, we found that the risk of CVD increased as the average weekly working hours increased, above a certain threshold," said Sadie H. Conway, Ph.D., lead author and assistant professor in the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health. Conway noted that among full-time workers, CVD risk appeared lowest between approximately 40 and 45 hours per week.

The researchers 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 such as angina, coronary heart disease or heart failure, heart attack, high blood pressure or stroke, occurred in about 43 percent of participants.

In one analysis, 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-time workers. Among those who averaged more than 30 hours of work per week, risk increased as weekly hours approached 40, but then decreased again between about 40 and 45 hours per week.

Beginning at approximately 46 hours per week, increasing work hours were progressively associated with increased risk of CVD. Compared to people who averaged 45 hours per week for 10 years or longer, overall CVD risk was increased by 16 percent for those who worked 55 hours per week and by 35 percent for those who worked 60 hours per week.

While previous research has suggested increased CVD risk with longer working hours, the new study is the first to focus on identifying and quantifying a "dose-response" effect. 

“This study provides specific evidence on long work hours and an increase in 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, titled Dose-Response Relationship Between Work Hours and Cardiovascular Disease Risk, was partially funded by grant number 5T42OH008421 from the National Institute for Occupational Safety and Health.

Co-authors from UTHealth School of Public Health included Lisa A. Pompeii, Ph.D., Robert E. Roberts, Ph.D., and David Gimeno, Ph.D. Jack L. Follis, Ph.D., from the University of St. Thomas was an additional co-author.

—adapted by Hannah Rhodes (Media Contact: 713-500-3030) from a press release by the Journal of Occupational and Environmental Medicine