The common heartbeat irregularity known as atrial fibrillation may raise the risk of developing cancer, a new study suggests.

It’s estimated that between 2.7 and 6.1 million people in the U.S. have atrial fibrillation (AF), which is the most common type of heartbeat irregularity. Atrial fibrillation is associated with an increased risk of major cardiovascular complications, such as heart attack and stroke. But a substantial portion of patients die from unrelated cardiovascular causes, and recent studies suggest a link between AF and cancer.

A Swiss team followed 35,000 initially healthy women for about 20 years, and found that those with new-onset atrial fibrillation had a higher risk of cancer, according to the new study published online by JAMA Cardiology.

The women were 45 years of age or older, and were free of AF, cardiovascular disease and cancer at the start of the study. During the follow-up, newly diagnosed AF and cancer were confirmed among 1,467 (4.2 percent) and 5,130 (14.8 percent) participants, respectively.  The researcher’s analysis indicated that new-onset AF was a significant risk factor for the subsequent diagnosis of cancer, even after extensive adjustment for other risk factors.

This higher risk persisted within three months of new-onset AF, but smaller risk increases persisted also time. Additionally, a trend toward an increased risk of cancer death was observed. Of the forms of cancer examined, AF was most strongly associated with colon cancer.

The study also found that women with newly diagnosed cancer had a higher risk of developing AF, but this was evident only within the first three months.

More research is needed to confirm the link between AF and cancer, as well as discover what might cause it, but in the meantime, they recommend that patients that are newly diagnosed with AF be monitored for cancer and vice versa.