***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND AND PURPOSE Subarachnoid hemorrhage ( SAH ) is more common in women than in men , but the role of hormonal factors in its etiology remains uncertain . The aim of this study was to examine the relationship between hormonal factors and  risk of SAH in women . METHODS This was a prospect i ve , multicenter , population -based , case-control study performed in 4 major urban centers in Australia and New Zeal and . Two hundred sixty-eight female cases of first-ever aneurysmal SAH occurred during 1995 - 1998 . Controls were 286 frequency-matched women from the general population of each center . Outcome measures included risk of SAH associated with use of oral contraceptive pills ( OCPs ) , hormone replacement therapy ( HRT ) , and various endogenous hormonal factors including menstrual patterns , parity , age at birth of first child , and breast-feeding practice s.  RESULTS Cases and controls did not differ with regard to menstrual and reproductive history except in age at birth of first child , where older age was associated with reduced risk of SAH ( odds ratio [ OR ] , 0.63 ; 95 % CI , 0.43 , 0.91 ) . Relative to never use of HRT , the adjusted OR for ever use of HRT was 0.64 ( 95 % CI , 0.41 , 0.98 ) , which did not alter significantly after further adjustment for possible confounding factors . Borderline evidence of an inverse association was detected for past use of  HRT  ( adjusted OR , 0.59 ; 95 % CI , 0.30 , 1.13 ) and current use of HRT ( adjusted OR , 0.67 ; 95 % CI , 0.40 , 1.13 ) , but there was no evidence of an association for use of OCPs ( adjusted OR , 0.97 ; 95 % CI , 0.58 , 1.60 ) . CONCLUSIONS The risks of SAH are lower in women whose first pregnancy is at an older age and women who have ever used  HRT but not OCPs . The findings suggest an independent etiologic role for hormonal factors in the pathogenesis of aneurysmal SAH and provide support for a protective role for HRT on risk of SAH in postmenopausal women PURPOSE To examine the risk factors for subarachnoid hemorrhage , for few prospect i ve data have been available on risk factors of subarachnoid hemorrhage among Japanese . METHODS A 9.4-year cohort study was conducted on 12,372 men and women , aged 40 - 69 years , free of history of stroke in six communities in Japan . RESULTS During the follow-up , seventy-one incidents of subarachnoid hemorrhage occurred . After adjusting for age , serum total cholesterol , body mass index , history of diabetes mellitus , blood pressure category and drinking category , current smokers had a significantly increased risk of subarachnoid hemorrhage compared with ' never-smokers ' : multivariate relative risk ( RR ) [ 95 % confidence interval ( 95 % CI ) ] = 3.1(1.4 - 6.9 ) for women , 1.5(0.4 - 5.3 ) for men and 2.7(1.3 - 5.5)for men and women . Hypertensives had a significantly increased risk of subarachnoid hemorrhage compared with normotensives : multivariate RR(95 % CI ) = 3.1(1.6 - 6.0 ) for women , 4.3(1.5 - 12.0 ) for men and 3.4(2.0 - 5.9 ) for men and women . For men , heavy drinkers ( > = 69 g per day ethanol ) , had a significantly increased risk of subarachnoid hemorrhage compared with ' never-drinkers ' : multivariate RR(95 % CI ) = 4.3(1.1 - 16.8 ) . For women , the relationship between heavy drinking and risk was not examined due to the small number of heavy drinkers ( n = 13 ) . Multivariate RR(95 % CI ) for men who smoked currently and drank heavily compared with men who did not smoke currently nor drink heavily was 6.0(1.8 - 20.1 ) . Multivariate RR(95 % CI ) for hypertensive men who drank heavily compared with normotensive or borderline hypertensive men who did not drink heavily was 13.0(3.9 - 43.9 ) . Multivariate RR(95 % CI ) for hypertensive men and women who smoked currently compared with normotensive or borderline hypertensive men and women who did not smoke currently was 6.1(1.3 - 28.7 ) for men and 6.3(1.4 - 28.0 ) for women . Furthermore , the combination of smoking , hypertension and heavy drinking raised the risk of subarachnoid hemorrhage substantially : multivariate RR(95 % CI ) = 17.5(3.4 - 90.2 ) . CONCLUSION Smoking and hypertension appeared to increase the risk of subarachnoid hemorrhage . For men , although the association of smoking with the risk of subarachnoid hemorrhage was weak compared with women , the combination of smoking , hypertension and heavy drinking increased the risk substantially . For women , smoking appeared to be an independent risk of subarachnoid hemorrhage , and the combination of smoking and hypertension increased the risk in additive fashion Data from 694 patients hospitalized with stroke were entered in a prospect i ve , computer-based registry . Three hundred and sixty-four patients ( 53 percent ) were diagnosed as having thrombosis , 215 ( 31 percent ) as having cerebral embolism , 70 ( 10 percent ) as having intracerebral hematoma , and 45 ( 6 percent ) as having subarachnoid hemorrhage from aneurysm or arteriovenous malformations . The 364 patients diagnosed as having thrombosis were divided into 233 ( 34 percent of all 694 patients ) whose thrombosis was thought to involve a large artery and 131 ( 19 percent ) with lacunar infa rct ion . Many of the findings in this study were comparable to those in previous registries based on postmortem data . New observations include the high incidence of lacunes and cerebral emboli , the absence of an identifiable cardiac origin in 37 percent of all emboli , a nonsudden onset in 21 percent of emboli , and the occurrence of vomiting at onset in 51 percent and the absence of headache at onset in 67 percent of hematomas Objective The overall incidence of aneurysmal subarachnoid haemorrhage ( aSAH ) in western population s is around 9 per 100 000 person-years , which confers to a lifetime risk of around half per cent . Risk factors for aSAH are usually expressed as relative risks and suggest that absolute risks vary considerably according to risk factor profiles , but such estimates are lacking . We aim ed to estimate incidence and lifetime risks of aSAH according to risk factor profiles . Methods We used data from 250 patients admitted with aSAH and 574 sex-matched and age-matched controls , who were r and omly retrieved from general practitioners files . We determined independent prognostic factors with multivariable logistic regression analyses and assessed discriminatory performance using the area under the receiver operating characteristic curve . Based on the prognostic model we predicted incidences and lifetime risks of aSAH for different risk factor profiles . Results The four strongest independent predictors for aSAH , namely current smoking ( OR 6.0 ; 95 % CI 4.1 to 8.6 ) , a positive family history for aSAH ( 4.0 ; 95 % CI 2.3 to 7.0 ) , hypertension ( 2.4 ; 95 % CI 1.5 to 3.8 ) and hypercholesterolaemia ( 0.2 ; 95 % CI 0.1 to 0.4 ) , were used in the final prediction model . This model had an area under the receiver operating characteristic curve of 0.73 ( 95 % CI 0.69 to 0.76 ) . Depending on sex , age and the four predictors , the incidence of aSAH ranged from 0.4/100 000 to 298/100 000 person-years and lifetime risk between 0.02 % and 7.2 % . Conclusions The incidence and lifetime risk of aSAH in the general population varies widely according to risk factor profiles . Whether persons with high risks benefit from screening should be assessed in cost-effectiveness studies Background and purpose The purpose of this study was to identify the risk factors predisposing to aneurysm rupture and to provide a reliable estimation for likelihood of rupture in unruptured intracranial aneurysms . Methods The authors performed a nested case-control study of 290 aneurysms ( 123 unruptured aneurysms and 167 ruptured aneurysms ) occurring during a prospect i ve cohort study in 1493 consecutive patients with newly diagnosed intracranial aneurysm and were treated in a single institute between January 1995 and December 2006 . Controls were matched for age , treatment group , number of lesion , sex , region and study period in which the incidence of ruptured and unruptured intracranial aneurysm was equivalently balanced . The authors assessed the predictive risk factors associated with aneurysmal rupture based on the clinical and angiographic findings reported in the patients ' medical records . Results Between January 1997 and December 2002 , 167 patients with ruptured intracranial aneurysms were assigned to group 1 , and 123 patients with unruptured intracranial aneurysms during the same period were assigned to group 2 . Aspect ratio ( OR 3.76 ) , maximum diameter of neck ( Nmax ) ≤3 mm ( OR 2.56 ) and family history of cerebrovascular disease ( OR 5.63 ) were strongly correlated with aneurysm rupture ( p<0.05 ) . Conclusions There are differences between the clinical and intrinsic characteristics of patients with unruptured and ruptured intracranial aneurysm . It will be helpful to make rational decisions regarding the optimal therapeutic strategy for unruptured intracranial aneurysm Background and Purpose — Although diabetes mellitus has been recognized as a risk factor for ischemic stroke , evidence is limited for ischemic stroke subtypes among Asians . Methods — A survey was conducted of a total of 13 129 men and 22 528 women aged 40 to 69 years at baseline . During the median 12.0-year follow-up , there were 526 incidences of ischemic strokes ( 259 lacunar infa rct ions , 91 large-artery occlusive , and 140 embolic infa rct ions ) . Results — The risk of ischemic stroke for both sexes was approximately 2 to 4 times higher for diabetic subjects than for those with normal glucose levels . Significant excess risks of lacunar and embolic infa rct ion for both sexes and of large-artery occlusive infa rct ions for women were also observed in diabetic subjects . Diabetes mellitus was not associated with risk of intraparenchymal or subarachnoid hemorrhage for either sex . Conclusions — Diabetes mellitus is a significant risk factor for ischemic stroke and all subtypes of ischemic stroke for middle-aged Japanese Background Prospect i ve studies on the risk factors for subarachnoid hemorrhage ( SAH ) are limited . Moreover , the effect of risk factors on the incidence rates of SAH is not well known about . Aims In this study , we aim ed to identify risk factors for SAH and characterize subgroups in a population with a high incidence of SAH . Methods After recording multiple potential risk factors for SAH at the time of enrolment , first ever SAH events between 1972 and 2009 were recorded through the nationwide Causes of Death Register and Hospital Discharge Register for the population -based cohort of 64 349 participants , who participated in the National FINRISK Study between 1972 and 2007 in Finl and . Results During the follow-up time of 1.26 million person-years ( median 17.9 years , range 0 to 37.9 years ) , 437 persons  experienced fatal or non-fatal SAH . Crude SAH incidence was 34.8 ( 95 % confidence interval : 31.7–38.2 ) per 100 000 person-years among ≥25-year-old persons . Female sex , high blood pressure values and current smoking were confirmed as risk factors for SAH . Previous myocardial infa rct ion , history of premature stroke ( any kind ) in mother and elevated cholesterol levels in men were identified as new risk factors for SAH . Depending on the combination of risk factors , SAH incidence varied between 8 and 171 per 100 000 person-years . Conclusions New and previously reported risk factors appear to have a much stronger association with the incidence of SAH than is ordinarily seen in cardiovascular diseases . Risk factor assessment s may facilitate the identification of high-risk persons who should be the focus of preventive interventions Background and Purpose — To identify risk factors for subarachnoid hemorrhage ( SAH ) and intracerebral hemorrhage , we design ed a case-control study of men and women 18 to 49 years of age ( the Hemorrhagic Stroke Project [ HSP ] ) . This report focuses on SAH . Methods — Patients were recru 
    Output:
    
Conclusion A potential decreased risk of aSAH  in DM patients was found in high quality studies .