Comparison of Blood Pressure–Associated Risk of Intracerebral Hemorrhage and Subarachnoid Hemorrhage

Intracerebral hemorrhage and subarachnoid hemorrhage have different pathogeneses and risk factor profiles. However, little information is available on the difference between intracerebral and subarachnoid hemorrhages in relation to blood pressure. We prospectively investigated the relationships between blood pressure and risks of stroke subtypes. We measured blood pressure and other cardiovascular risk factors in 100,147 men and 59,558 women 35 to 59 years of age in 1990 and 1992. Outcomes were fatal and nonfatal events of stroke and its subtypes from 1993 to 2002. Independent relationships between baseline blood pressure and stroke subtypes were assessed using Cox's proportional hazard models. During the 10 years, 1714 ischemic and 1159 hemorrhagic strokes (742 intracerebral and 308 subarachnoid hemorrhages) occurred. Blood pressure was related more closely with hemorrhagic stroke than ischemic stroke, and the difference was more prominent in women. Among the subtypes of hemorrhagic stroke, intracerebral hemorrhage was more closely related with blood pressure than subarachnoid hemorrhage. For each 20 mm Hg increase in systolic blood pressure, adjusted relative risks of ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage were 1.79 (95% confidence interval, 1.68 to 1.90), 2.48 (2.30 to 2.68), and 1.65 (1.38 to 1.97) in men, and 1.64 (1.42 to 1.89), 3.15 (2.61 to 3.80), and 2.29 (1.82 to 2.89) in women, respectively. In conclusion, blood pressure is more closely related with intracerebral hemorrhage than subarachnoid hemorrhage, thus proportion of intracerebral hemorrhage in hemorrhagic stroke may affect the association between blood pressure and hemorrhagic stroke. Our data also emphasize the importance of blood pressure control for the prevention of stroke, especially in countries with a high incidence of intracerebral hemorrhage.