Smokers hear it all the time. They should quit smoking. But for many, it’s much easier said than done. The addiction is strong. But if any smoker needs yet another reason to quit, it may be this one: Smokers who have atrial fibrillation, an irregular heartbeat, can cut their risk of having a stroke if they quit their cigarette habit.

Atrial fibrillation, or a-fib, is a common heart disorder that affects up to 6 million people in the United States. It also causes thousands of deaths. Researchers who presented a study on the connection between smoking and a-fib said that 1 in 4 middle-aged adults in Europe and the U.S. will develop a-fib. People with a-fib are 5 times more likely to have a stroke than people who don’t have the heart condition. Stroke is the most common cause of death in this group.

The study included over a half a million patients who were newly diagnosed with a-fib and they were followed for an average of 3 years. The researchers found that while patients who had quit smoking still had a higher risk of stroke overall, they did drop their risk and had a 30% lower probability than those who continued to smoke. Heavier smokers, those who smoked at least 20 cigarettes a day for 30 years didn’t see such a big drop, but they still did see a benefit. People who had just begun to smoke before their diagnosis raised their risk of stroke by 84% and those who were “persistent smokers” had a 66% higher risk.

Why is the stroke risk higher for smokers who have a-fib? A-fib causes your blood to pool in parts of your heart and blood clots can form. If they dislodge, they can travel to the brain and cause a stroke. "Smoking precipitates blood clots that could lead to a stroke, which may be why giving up lowers risk,” said study author So-Ryoung Lee, MD, of Seoul National University Hospital, Korea, in a press release. “The remaining stroke risk after quitting might be through the damage already caused to the arteries - called atherosclerosis."