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Blood pressure and smoking seem to have a significant impact on the risk of bleeding in the brain
A recent study by German and Dutch researchers provides evidence of a connection between the occurrence of aneurysmal cerebral hemorrhage and the risk factors of high blood pressure and smoking.
Risk factors high blood pressure and smoking
A new study by German and Dutch scientists provided evidence of a connection between the occurrence of aneurysmal cerebral hemorrhage and the risk factors of hypertension and smoking. The comprehensive meta-analysis was published in the journal "JAMA Neurology" by researchers from the Neurosurgical Clinic at the University Medicine Mannheim (UMM) together with scientists from the Neurological Clinic at the University of Utrecht, the Netherlands.
Special form of stroke
Aneurysmal subarachnoid hemorrhage (SAB) is a special form of stroke in which blood gets into the subarachnoid space filled with cerebral fluid, which protects the brain and spinal cord.
As a UMM statement explains, this form of cerebral hemorrhage often occurs when an aneurysm, a sac-like extension of an artery, tears at the base of the brain.
Subarachnoid hemorrhages make up only about five percent of all strokes, but the consequences are extremely threatening:
Half of those affected are under the age of 55, a third die within the first few days to weeks after the bleeding has occurred, and around a third of the survivors remain permanently dependent on help.
The meta-analysis of the German and Dutch scientists now reveals for the first time a worldwide decrease in the occurrence of aneurysm-related hemorrhages in parallel with the decrease in hypertension and smoking.
The goal of the researchers was not only to shed light on the apparently heterogeneous distribution of the incidence of SAB, both temporally and spatially, but also to identify potential determinants that could be responsible for a decrease in this disease.
The number of diseases has decreased
The starting point of the project was the recently published, sometimes contradictory, data from various register-based or regional studies that document a decrease in the incidence of subarachnoid bleeding.
The systematic review has incorporated metadata from all worldwide, population-based stroke studies over the past 60 years. On the one hand, the study recorded the occurrence of aneurysmal cerebral hemorrhage regionally and its frequency over time.
In addition, the meta-analysis shows for the first time the development of the factors blood pressure and smoking in relation to the SAB incidence.
There is clear evidence of a connection between the occurrence of aneurysmal cerebral hemorrhage and the risk factors of high blood pressure and smoking.
Specifically, the analysis of the data from 75 studies with a total of more than 8,000 people from 32 countries shows that the incidence of cerebral bleeding has decreased significantly in the past decades:
Between 1980 and 2010, the overall incidence of aneurysmal subarachnoid hemorrhage decreased by around 40 percent worldwide. Here, however, large regional differences were demonstrated:
The incidence decreased in Europe by 41 percent, in Asia by 46 percent and in North America by 14 percent. In contrast, the incidence of SAB in Japan has increased by 59 percent in the past three decades. The occurrence of SAB is also distributed differently according to age and gender.
Decrease in parallel with the decrease in systolic blood pressure and smoking prevalence
It is striking that the development or decrease in SAB incidence worldwide runs parallel to the decrease in systolic blood pressure and smoking prevalence in the same period.
"A mental game: If the decrease in SAB incidence were actually directly related to the reduction in systolic blood pressure, this would mean that the SAB incidence would decrease by 7.1 percent with every decrease in blood pressure by 1 mmHg," explains the first author the scientific publication, Professor Dr. Nima Etminan.
"And in relation to smoking prevalence, this means that the SAB incidence decreases by 2.4 percent per percent decrease in smoking prevalence," said the senior consultant of the UMM Neurosurgical Clinic.
Of course, the parallel development of blood pressure drop and smoking prevalence with the incidence of subarachnoid hemorrhage only suggests a causal relationship.
The available data cannot prove this, quantitative data for these risk factors on a population basis or at the level of individual patients would be necessary.
Nevertheless, the association found in the study supports preventive approaches to control the risk factors of hypertension and smoking in order to reduce the risk of aneurysmal hemorrhage.
Reduce risk of aneurysmal hemorrhage
At the same time, the authors are currently investigating the scientific question of whether lowering blood pressure in patients with accidentally discovered aneurysms, who are not primarily treated but controlled by imaging, has a positive effect on the development of the aneurysms.
This is being done as part of the prospective phase III study PROTECT-U (www.protect-u-trial.com/) at various neurovascular centers in Germany, the Netherlands and soon also in Canada.
The present work also offers starting points for further studies, the results of which - if they lead to appropriate strategies of primary prevention - could actually help to further reduce the risk of aneurysmal hemorrhage:
This would be a closer look at the regional differences in the incidence of SAB and their reduction, the regional differences in age and gender incidences and their relationship to more accurate, quantitative data on smoking behavior. (ad)