As of 2015, approximately 6 million Americans have unruptured brain aneurysms, according to the Brain Aneurysm Foundation. Approximately 30,000 people in the United States suffer from a ruptured brain aneurysm yearly. Therefore, the average brain aneurysm patient has an 0.5 percent chance, or odds of one in 200, of developing a ruptured aneurysm, notes Math Planet. The annual rate of rupture is eight to 10 per 100,000 people in the United States.
A brain aneurysm ruptures every 18 minutes, says the Brain Aneurysm Foundation. Approximately 40 percent, or 12,000, cases are fatal. Of the 18,000 survivors, about 66 percent suffer permanent neurological damage, while four out of seven people who recover from a ruptured aneurysm have disabilities. Most brain aneurysms occur in people between the ages of 35 and 60, although anyone can suffer from this malady.
Doctors classify brain aneurysms by size, according to the National Institute of Neurological Disorders and Stroke. Small aneurysms measure less than 11 millimeters in diameter, which approximates the size of a large pencil eraser. Large aneurysms measure 11 to 25 millimeters, or about the size of a dime. Giant aneurysms grow to more than 25 millimeters wide, which represents the width of a quarter. Larger aneurysms have a greater chance of rupturing than smaller ones. Possible risk factors for a ruptured aneurysm include high blood pressure, alcoholism, drug abuse and smoking.