Incidence of subarachnoid haemorrhage: a systematic review with emphasis on region, age, gender and time trends

Abstract

Background and aim: To update our 1996 review on the incidence of subarachnoid haemorrhage (SAH) and assess the relation of incidence with region, age, gender and time period. Methods: We searched for studies on the incidence of SAH published until October 2005. The overall incidences with corresponding 95% confidence intervals were calculated. We determined the relationship between the incidence of SAH and determinants by means of univariate Poisson regression. Results: We included 51 studies (33 new), describing 58 study populations in 21 countries, observing 45 821 896 person-years. Incidences per 100 000 person-years were 22.7 (95% CI 21.9 to 23.5) in Japan, 19.7 (18.1 to 21.3) in Finland, 4.2 (3.1 to 5.7) in South and Central America, and 9.1 (8.8 to 9.5) in the other regions. With age category 45-55 years as the reference, incidence ratios increased from 0.10 (0.08 to 0.14) for age groups younger than 25 years to 1.61 (1.24 to 2.07) for age groups older than 85 years. The incidence in women was 1.24 (1.09 to 1.42) times higher than in men; this gender difference started at age 55 years and increased thereafter. Between 1950 and 2005, the incidence decreased by 0.6% (1.3% decrease to 0.1% increase) per year. Conclusions: The overall incidence of SAH is approximately 9 per 100 000 person-years. Rates are higher in Japan and Finland and increase with age. The preponderance of women starts only in the sixth decade. The decline in incidence of SAH over the past 45 years is relatively moderate compared with that for stroke in general.

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“…One hypothesis for this is based on the fact that with the decrease in plasma levels of sex hormones in post menopausal women, there would be an inhibition of collagen formation, and thus can affect the brain blood vessels. 10,11 The point prevalence of multiple aneurysms in our series was 26%, falling between the average suggested by the literature, 17% to 30%. Studies say that the prevalence of multiple aneurysms changes according to the prevalence of risk factors for aneurysm formation in various populations.…”

Estrogen Deficiency Promotes Cerebral Aneurysm Rupture by Upregulation of Th17 Cells and Interleukin‐17A Which Downregulates E‐Cadherin

“…In humans, aneurysms occur more often in women (70–75%) pre‐ and postmenopause 2. However, aneurysm ruptures occur most often in postmenopausal women 3, 4…”

“…Estrogen deficiency has been linked to aneurysm formation and rupture. Approximately 70% to 75% of aneurysms occur in women,2 with postmenopausal women having the highest risk for aneurysm rupture 3, 4. Several studies have investigated estrogen deficiency and CA5, 6, 7, 8; however, the mechanism remains unknown.…”

Inflammation in human cerebral aneurysms: pathogenesis, diagnostic imaging, genetics, and therapeutics

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