Over half of all cases of the most common type of heart rhythm disturbance could be avoided by "clean living", such as avoiding smoking and eating more healthily, say scientists.
If individuals were to maintain a healthy weight and normal blood pressure and abstain from tobacco 57% of cases of atrial fibrillation (AF) could be averted, the US experts say.
The study in Circulation journal is based on nearly 15,000 patients.
AF is a major cause of stroke.
Yet many people are unaware that they have this heart condition because often it causes very few symptoms.
Experts believe up to 500,000 people in the UK have AF.
The condition can be treated with medication to slow the irregular heartbeat and blood-thinning drugs to reduce stroke risk, but the latest research shows how much illness could be avoided by simple lifestyle measures.
Dr Alvaro Alonso, who led the research at the University of Minnesota School of Public Health, said: "We now know that a significant proportion of all cases of atrial fibrillation can be avoided.