Had an approximately two-fold higher risk of HS compared to non-migraineurs (adjusted HR 2.13; 95 CI 1.71 ?2.67). It has been controversial whether migraine is linked to an increased risk of HS. Most previous studies were unable to identify a link between HS and migraine [5,9,10], only relatively few studies have reported a positive association between migraine and HS. In an epidemiologic study based on the Dijon Stroke Registry, the frequency of a history of migraine was higher in patients with cerebral hemorrhage (3.6 ) and subarachnoid hemorrhage (6.3 ) than those with ischemic stroke (1.8 ) [7]. Furthermore, a cohort study using data from Women’s health study showed that migraine with aura was a risk factor of HS (adjusted HR 2.25, 95 CI, 1.11 ?4.54) [8]. Nevertheless, the mechanism underlying the positive association between migraine and HS is still unclear. We propose the following possible explanations. Migraine has been linked to dysfunction of cerebrovascular autoregulation [12], which, in turn, has been suggested to be related to occurrence of HS [13?5]. Thus, the association between migraine and HS found in our study may be explained, at least in part, by the association between migraine and dysfunction of cerebrovascular autoregulation. In addition, reversible cerebral vasoconstriction syndrome (RCVS), characterized by reversible constriction of the cerebral arteries, has been associated with migraine [16,17]. Because a higher risk of HS has been reported in patients with RCVS [17,18], the link between RCVS and migraine may also contribute to 1527786 the higher risk of HS in migraineurs. In our study, the comparison of HS subtype showed that subjects in the migraine group are more likely to have subarachnoid hemorrhage than the non-migraine group. Because subarachnoid hemorrhage has been 14636-12-5 price considered as a major type ofFigure 1. Hemorrhagic stroke-free survival rates for the migraine group (dotted line) and the non-migraine group (solid line). doi:10.1371/journal.pone.0055253.gMigraine and Risk of Hemorrhagic StrokeTable 2. Crude and adjusted hazard Nafarelin web ratios (HR) for the occurrence of hemorrhagic stroke during the two-year follow-up period in the migraine and non-migraine groups.Occurrence of hemorrhagic stroke Variable Migraine (vs. non-Migraine) Age (year) Sex (female vs. male) Hypertension With antihypertensive medication (vs. no hypertension) Without antihypertensive medication (vs. no hypertension) Diabetes (yes vs. no) Hyperlipidemia (yes vs. no) Coronary heart disease (yes vs. no) Chronic rheumatic heart disease (yes vs. no) Other heart disease (yes vs. no) Use of anticoagulant medication (yes vs. no){Crude HR (95 CI) 2.22* (1.78 ?2.77) 1.05* (1.04 ?1.06) 0.54* (0.44 ?0.66) 4.18* (3.34 ?5.25) 3.44* (2.20 ?5.37) 3.24* (2.46 ?4.27) 2.04* (1.48 ?2.83) 2.82* (2.07 ?3.86) 5.40* (2.56 ?11.40) 2.91* (2.12 ?4.00) 6.50 (2.43 ?17.42){{Adjusted 24786787 HR (95 CI)P value for adjusted HR ,0.0001 ,0.0001 ,0.2.13 (1.71 ?2.67) 1.04 (1.03 ?1.05) 0.62 (0.51 ?0.77)1.74 (1.34 ?2.26) 1.74 (1.10 ?2.75) 1.52 (1.14 ?2.04) NS NS 2.62 (1.24 ?5.57) NS NS,0.0001 0.0181 0.0046 NS NS 0.0120 NS NS*P,0.0001, P,0.001 in the univariate analysis. { The adjusted hazard ratios were derived from the final multiple regression model. Abbreviations: CI, confidence interval; NS, non-significant. doi:10.1371/journal.pone.0055253.themorrhagic manifestation in patients with RCVS [17,19], the predisposition of subarachnoid hemorrhage in migraineurs may further support our hypothe.Had an approximately two-fold higher risk of HS compared to non-migraineurs (adjusted HR 2.13; 95 CI 1.71 ?2.67). It has been controversial whether migraine is linked to an increased risk of HS. Most previous studies were unable to identify a link between HS and migraine [5,9,10], only relatively few studies have reported a positive association between migraine and HS. In an epidemiologic study based on the Dijon Stroke Registry, the frequency of a history of migraine was higher in patients with cerebral hemorrhage (3.6 ) and subarachnoid hemorrhage (6.3 ) than those with ischemic stroke (1.8 ) [7]. Furthermore, a cohort study using data from Women’s health study showed that migraine with aura was a risk factor of HS (adjusted HR 2.25, 95 CI, 1.11 ?4.54) [8]. Nevertheless, the mechanism underlying the positive association between migraine and HS is still unclear. We propose the following possible explanations. Migraine has been linked to dysfunction of cerebrovascular autoregulation [12], which, in turn, has been suggested to be related to occurrence of HS [13?5]. Thus, the association between migraine and HS found in our study may be explained, at least in part, by the association between migraine and dysfunction of cerebrovascular autoregulation. In addition, reversible cerebral vasoconstriction syndrome (RCVS), characterized by reversible constriction of the cerebral arteries, has been associated with migraine [16,17]. Because a higher risk of HS has been reported in patients with RCVS [17,18], the link between RCVS and migraine may also contribute to 1527786 the higher risk of HS in migraineurs. In our study, the comparison of HS subtype showed that subjects in the migraine group are more likely to have subarachnoid hemorrhage than the non-migraine group. Because subarachnoid hemorrhage has been considered as a major type ofFigure 1. Hemorrhagic stroke-free survival rates for the migraine group (dotted line) and the non-migraine group (solid line). doi:10.1371/journal.pone.0055253.gMigraine and Risk of Hemorrhagic StrokeTable 2. Crude and adjusted hazard ratios (HR) for the occurrence of hemorrhagic stroke during the two-year follow-up period in the migraine and non-migraine groups.Occurrence of hemorrhagic stroke Variable Migraine (vs. non-Migraine) Age (year) Sex (female vs. male) Hypertension With antihypertensive medication (vs. no hypertension) Without antihypertensive medication (vs. no hypertension) Diabetes (yes vs. no) Hyperlipidemia (yes vs. no) Coronary heart disease (yes vs. no) Chronic rheumatic heart disease (yes vs. no) Other heart disease (yes vs. no) Use of anticoagulant medication (yes vs. no){Crude HR (95 CI) 2.22* (1.78 ?2.77) 1.05* (1.04 ?1.06) 0.54* (0.44 ?0.66) 4.18* (3.34 ?5.25) 3.44* (2.20 ?5.37) 3.24* (2.46 ?4.27) 2.04* (1.48 ?2.83) 2.82* (2.07 ?3.86) 5.40* (2.56 ?11.40) 2.91* (2.12 ?4.00) 6.50 (2.43 ?17.42){{Adjusted 24786787 HR (95 CI)P value for adjusted HR ,0.0001 ,0.0001 ,0.2.13 (1.71 ?2.67) 1.04 (1.03 ?1.05) 0.62 (0.51 ?0.77)1.74 (1.34 ?2.26) 1.74 (1.10 ?2.75) 1.52 (1.14 ?2.04) NS NS 2.62 (1.24 ?5.57) NS NS,0.0001 0.0181 0.0046 NS NS 0.0120 NS NS*P,0.0001, P,0.001 in the univariate analysis. { The adjusted hazard ratios were derived from the final multiple regression model. Abbreviations: CI, confidence interval; NS, non-significant. doi:10.1371/journal.pone.0055253.themorrhagic manifestation in patients with RCVS [17,19], the predisposition of subarachnoid hemorrhage in migraineurs may further support our hypothe.