Do you worry that your workaholic ways are killing you? A new study says you may be right.

In an analysis of more than half a million men and women from around the world, those who put in long hours at the office were 33 percent more likely to suffer a stroke than their colleagues who clocked out earlier. Even those who worked just over 40 hours per week saw a significant increase in stroke risk, according to results in the journal Lancet.

An international team of researchers gathered data on hundreds of thousands of workers in the U.S., Australia, Israel and eight countries in Europe who participated in various long-term studies. The volunteers told researchers how many hours they worked per week. Then they were tracked for several years.

The researchers identified 528,908 people who were stroke-free when they joined a study. Over the next seven or so years, 1,722 of them suffered a stroke. But the odds weren’t spread equally — the more they worked, the greater the risk.

Compared to people who worked 35 to 40 hours per week, those who logged 41 to 48 hours per week were 10 percent more likely to suffer a stroke, the researchers found. Workers who put in 49 to 54 hours per week were in greater peril — their stroke risk was 27 percent higher than for the baseline group. Worst off were those who worked at least 55 hours per week and saw their stroke risk rise 33 percent.

This dose-response relationship between working hours and stroke risk was seen in both men and women, and in workers in all four regions studied, the researchers wrote. The results were adjusted to account for the age, gender and socioeconomic status of each study volunteer as well as factors such as smoking history, alcohol consumption and body mass index.