Atrial fibrillation is an irregular heart rhythm that increases the risk of stroke, heart failure, and other heart-related complications. It is most commonly found in people over the age of 65, especially those with a history of heart disease, high blood pressure, diabetes, or obesity. Other risk factors include a family history of atrial fibrillation, smoking, excessive alcohol use, and thyroid disease. In addition, some forms of medication can increase the risk of atrial fibrillation, as can certain medical procedures. As such, the group of people with the highest risk of atrial fibrillation are those aged over 65 with existing heart conditions, high blood pressure, diabetes, obesity, and/or family history, as well as those who smoke, drink excessively, use certain medications, or have had medical procedures.