Most people don’t look forward to tedious overtime hours, mostly because relaxing sounds better than logging in extra hours at the office. Now experts say there are tangible reasons why slaving away at your desk isn’t always the best idea. New data shows there’s a definite correlation between working above and beyond the average work week and the onset of heart disease.

Appearing in the European Heart Journal, the study followed more than six thousand civil servants for a little over eleven years, monitoring participants’ health issues while tracking time spent at work. During that time, the study subjects experienced three-hundred-and-sixty-nine critical heart episodes, including both fatal and not non-fatal attacks. Although there was no apparent link between heart disease and working only one or two extra hours a week, those who worked four or more extra hours experienced a sixty percent higher incidence of coronary disease than those who worked no overtime. Even when the researchers took into account twenty-one other risk factors, the percentages barely changed.

The scientists did note that the correlation might be more ancillary than direct. For example, one explanation for the increased risk could be that those who work excessive hours are simply more prone to risk factors for heart disease, dramatically increasing the likelihood they’ll get sick. Another thought is that the stress produced by working longer hours can adversely affect metabolism.

Scientists say future studies should look at whether working longer hours affects changes in daily life, mental health and other factors, such as elevated blood pressure, blood glucose and cholesterol.

Worried your workday is too long? Try kicking back. A little relaxation never hurt anyone.