Putting in long hours at the office can be tough mentally, and now there’s new evidence that it may be bad for your physical health, too. According to findings published in the European Heart Journal, working more than 55 hours per week is linked to an increased risk of developing an irregular heart rhythm known as atrial fibrillation.

Often referred to as AFib, atrial fibrillation has been linked to stroke and heart failure as well as other serious health conditions. The new report, which combined the findings from a number of previous studies, looked at data from 85,000 participants in five different countries. The analysis found that those who worked 55 or more hours per week were 40 percent more likely to develop AFib than those who worked between 35 and 40 hours per week, according to a TIME piece about the findings. 

These statistics seem ominous, but it’s important to note that the study did have a few major limitations. For starters, it proved correlation, not causation, between hours worked and AFib risk, meaning the researchers can’t make any definitive claims about whether working long hours directly caused the heart issue. The researchers also can’t say for sure what aspect of long work weeks may have contributed to participants’ heart issues, though they suspect it’s a combination of stress and exhaustion. The study also failed to identify the occupations of participants, which could be significant, as some jobs require employees to work longer shifts than others.

However, this study is not the first to suggest that working long hours could be detrimental to your health. For example, in a 2016 study published in the Journal of Occupational and Environmental Medicine and cited by TIME, individuals who worked more than 60 hours a week were more likely to develop arthritis, diabetes, asthma and cancer than those who less than 40 hours per week.

Long hours are often unavoidable, but that doesn’t mean you have to resign yourself to health issues down the road. Setting boundaries within your work environment, along with taking time to recover and recharge after a particularly draining period at work, can help you put your well-being first and keep your job from becoming a health hazard.

Read more about the findings in TIME.