Epidemiology

Worldwide, almost 500,000 individuals develop a SAH caused by an aneurysm each year, with almost two-thirds of these in low- and middle-income countries.[6] The global incidence of SAH declined between 1980 and 2010 which may parallel the global decreases in blood pressure and smoking prevalence.[7]​ However, a large variation in SAH incidence exists according to region, age, and sex. 

The incidence in the US is between 6 and 8 cases out of 100,000 per year.[6]​[8]​​ A higher incidence in Hispanic populations compared with in non-Hispanic populations has also been noted in some areas of the US.[9] Some countries have seen increases in the incidence of SAH. In Japan, the incidence of SAH increased between 1980 and 2010, especially in women older than 55 years.[10] Incidence also increases with age. The average age at onset is between 50 and 55 years.[1][11][12] SAH is 1.6 times more common in women than in men, and 2.1 times more common in black people than in white people.[8][13]

SAH accounts for about 5% of all strokes.[14]

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