High blood pressure and valvular heart disease are the most common alterable risk factors for AF.Other heart-related risk factors include heart failure, coronary artery disease, cardiomyopathy, and congenital heart disease. In the developing world valvular heart disease often occurs as a result of rheumatic fever. Lung-related risk factors include COPD, obesity, and sleep apnea. Other factors include excess alcohol intake, tobacco smoking, diabetes mellitus, and thyrotoxicosis. However, half of cases are not associated with any of these risks.