Epidemiology

Worldwide, almost 500,000 individuals develop a subarachnoid hemorrhage (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]

Risk factors

strongVIEW ALL

hypertension

Hypertension is an important risk factor (relative risk is 2.8) and is potentially modifiable.[26][29][30][31][32][33][34]

smoking

Smoking is one of the most important potentially modifiable risk factors.[26][30][31][32][33][34][35] Relative risk is 1.9.[10][11]

family history

First-degree relatives of patients with subarachnoid hemorrhage (SAH) have a 4% prevalence of harboring cerebral aneurysms and a three-fold to seven-fold increased risk of having SAH than the general population.[15][34] The risk is highest when the affected relative is a sibling.[29] Population studies of aneurysmal SAH have demonstrated that 9% to 14% of patients with a SAH have a family history of SAH in a first-degree relative.[25]

Having two or more first-degree relatives with SAH has a relative risk of SAH of 6.6.[15] Patients who have two or more first-degree relatives with SAH are potential candidates for aneurysm screening.[25][29]

autosomal dominant polycystic kidney disease (ADPKD)

ADPKD is an important risk factor (relative risk is 4.4).[29] One quarter of patients with ADPKD have aneurysms at autopsy, and 2% to 8% of patients with aneurysms have ADPKD.[36]

Individuals with ADPKD are potential candidates for aneurysm screening.[25][29]

weakVIEW ALL

alcohol use

The relationship of subarachnoid hemorrhage to excessive alcohol use is less robust than that of hypertension or smoking.[30][31][34][35]

cocaine use

The relationship of subarachnoid hemorrhage to cocaine use is less robust than that of hypertension or smoking.

Marfan syndrome

Connective tissue disorder with an increased risk for aneurysmal formation and subarachnoid hemorrhage.[36]

Ehlers-Danlos syndrome

Connective tissue disorder with an increased risk for aneurysmal formation and subarachnoid hemorrhage.[36]

pseudoxanthoma elasticum

Connective tissue disorder with an increased risk for aneurysmal formation and subarachnoid hemorrhage.[36]

neurofibromatosis type I

Connective tissue disorder with an increased risk for aneurysmal formation and subarachnoid hemorrhage.[36]

Use of this content is subject to our disclaimer