A new study published in the online edition of European Heart Journal on May 12 found clocking in overtime may adversely affect a healthy heart.

Marianna Virtanen, PhD, an epidemiologist at the Finnish Institute of Occupational Health in Helsinki and University College London, said: "The association between long hours and coronary heart disease was independent of a range of risk factors that we measured at the start of the study, such as smoking, being overweight, or having high cholesterol."

"Our findings suggest a link between working long hours and increased CHD [coronary heart disease] risk, but more research is needed before we can be confident that overtime work would cause CHD. In addition, we need more research on other health outcomes, such as depression and type 2 diabetes," cautioned Virtanen.

This study analyzed the results from 6014 British civil servants (4262 men and 1752 women) aged 39-61, and, during an 11-year follow-up the research team from Finland, London and France, identified 369 cases of fatal CHD, non-fatal heart attacks (myocardial infarctions) or angina. The team then took into account 21 risk factors including age, sex, marital status and occupational grade concluding that working at minimum of three to four hours overtime was associated with a 60 percent higher rate of CHD compared with those that didn't work overtime.

Mika Kivimäki, professor of social epidemiology at University College London and senior author of the study, and her team suggest that other factors could be responsible for the link between overtime and heart disease, for instance: workers with a type A personality, poor sleeping patterns, psychological stress, high blood pressure related to work stress, "sickness presenteeism" (not likely to address health problems), and those with positions with little control over work-related decisions.

Due to the fact that the study was also conducted only with civil servants, it is unclear if other forms of employment would produce similar results. That being said it is clear, even though the current findings do not reveal all the factors that may play a role in how working extra hours increases CHD, it would be best the next time you are faced with extra work to negotiate for only an extra hour or two for your heart's sake.

"Future research will include analysing data over periods of time to examine whether working long hours predicts changes in life style, mental health and traditional risk factors, such as blood pressure, blood glucose and cholesterol. We hope that this research will increase understanding of the mechanisms underlying the association between long working hours and coronary heart disease. We will also examine whether overtime work increases the risk of depression, as recent research suggests that depression increases the risk of coronary heart disease," said Kivimäki.

It could be the case in the near future that getting too much extra work will be against healthy policy and workers' rights.

Full study, "Overtime work and incident coronary heart disease: the Whitehall II prospective cohort study": http://eurheartj.oxfordjournals.org