May 13, 2010 -- Working a lot of overtime may be good for your wallet, but it may be bad for your heart.
In a study of about 6,000 British civil servants followed for about a decade, working three or more hours of overtime a day was associated with a 60% increased risk of heart-related health issues, including heart attack, angina, and death from heart disease.
The association was seen even after researchers considered the impact of well-established heart disease risk factors like smoking, obesity, and high cholesterol.
Lead researcher Marianna Virtanen, PhD, tells WebMD that for the white collar civil servants in the study, working overtime was associated with more type A behavior traits like aggression, hostility, competitiveness, psychological distress, and sleep problems.
The research appears online in the European Heart Journal.
“The importance of having a good balance between work time, leisure time, and family time may be more important for the heart than has been appreciated,” she says.
Virtanen is a senior researcher and psychologist with the Finnish Institute of Occupational Health and the University College London.
Men, Married Workers Logged More Hours
The study participants were enrolled in the larger, ongoing Whitehall II health study of London-based civil service workers begun in the mid-1980s. The data on working hours were introduced in the study starting in the early 1990s.
Workers were in their late 30s to early 60s at enrollment, and they were followed for an average of 11.2 years for the overtime analysis.
During this time, 369 incidences of heart attack, angina, or heart-related death were reported.
One or two hours over the seven hours considered normal for a workday in the U.K. had little impact on heart health.
But working 10 or more hours a day was associated with a 60% increase in heart-related events.
Just over half of the study participants (54%) reported working no regular overtime, 15% reported working two extra hours a day, and 10% reported working three or four extra hours.
Men were six times more likely than women to work three or more hours of overtime a day, and married workers were almost nine times more likely than single workers to spend this much time at work.
Nearly 60% of the respondents who reported spending 10 or more hours a day at work characterized their job demands as “high,” while just 8% considered their job demands to be “low.”
Sixty-four percent of the employees who worked the longest hours reported a lot of latitude in making work decisions, while 13% reported little latitude.
Overtime Has ‘Moderate’ Impact on Heart
Virtanen characterized the impact of overtime on heart risk as "moderate."
“Certainly these findings need to be replicated, and we also need more research on other health outcomes, including type 2 diabetes,” she says.
Virtanen says it is not clear if the findings apply to blue-collar workers, who may have less discretion than white-collar workers over the hours they work.
The Whitehall II study is funded, in part, by the British Heart Foundation and the U.S. National Institutes of Health.
In an editorial published with the study, cardiovascular researcher Gordon T. McInnes, MD, of Scotland’s University of Glasgow, agreed that more study is needed to confirm an independent association between overtime-related work stress and cardiovascular disease.
But he noted that a growing body of research is linking longer work days with health problems, including high blood pressure.
He concludes that researchers should examine “whether interventions designed to reduce overtime work could alter the risk of cardiovascular disease.”