Blood pressure and smoking seem to significantly influence the risk of cerebral hemorrhage
A recent study by German and Dutch researchers provides evidence of a link between the occurrence of aneurysmal brain haemorrhage and the risk factors of hypertension and smoking.
Risk factors for hypertension and smoking
In a recent study by German and Dutch scientists, evidence was found for a link between the occurrence of aneurysmal brain haemorrhage and the risk factors of hypertension and smoking. The comprehensive meta-analysis was published in the journal "JAMA Neurology" by researchers from the Neurosurgery department of the University Medical Center Mannheim (UMM) in collaboration with scientists from the Department of Neurology, University of Utrecht, the Netherlands.
Special form of stroke
Aneurysmal subarachnoid haemorrhage (SAB) is a special form of stroke in which the blood enters the subarachnoid space that is filled with cerebrospinal fluid and protects the brain and spinal cord.
As explained in a UMM statement, this type of brain haemorrhage often occurs when an aneurysm, a saccular extension of an artery, breaks at the brain base.
Although subarachnoid haemorrhage accounts for only about five percent of all strokes, the consequences are very threatening:
Half of the victims are younger than 55, one third die within the first days to weeks after the start of the bleeding and about one third of the survivors are permanently dependent on help.
The meta-analysis of German and Dutch scientists now reveals for the first time a worldwide decrease in the incidence of aneurysm-related cerebral hemorrhage in parallel with the decline in hypertension and smoking.
The aim of the researchers was not only to shed some light on the apparently heterogeneous temporal and spatial distribution of the incidence of SAB, but also to identify possible determinants that could be responsible for the decline of this disease.
Number of diseases decreased
The starting point of the project was recently published, sometimes contradictory data from different registry-based or regional studies, which document a decrease in the incidence of subarachnoid hemorrhage.
The systematic review included metadata from all global, population-based stroke studies over the past 60 years. On the one hand, the study captures the occurrence of aneurysmal strokes regionally and their frequency over time.
Moreover, the meta-analysis presents 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 link between the occurrence of aneurysmal haemorrhages and the risk factors of hypertension and smoking.
Specifically, the analysis of data from 75 studies with more than 8,000 people from 32 countries shows that the incidence of cerebral haemorrhage has decreased significantly in recent decades:
Between 1980 and 2010, the incidence of aneurysmal subarachnoid haemorrhage decreased roughly by about 40 percent. Here, however, large regional differences were detected:
The incidence in Europe fell by 41 percent, in Asia by 46 percent and in North America by 14 percent. In contrast, the incidence of SAB in Japan increased by 59 percent over the past three decades. The incidence of SAB is also divided according to age and gender.
Decline in parallel with the decrease in systolic blood pressure and the prevalence of smoking
It is striking that the development or decrease of the SAB incidence worldwide is parallel to the decrease in systolic blood pressure and the prevalence of smoking in the same period.
"A state of mind: if the decrease in SAB incidence was actually directly related to the reduction in systolic blood pressure, this would mean that the incidence of SAB would decrease by 7.1 percent with each reduction in blood pressure by 1mmHg," explains the lead author from the scientific publication, Professor Nima Etminan.
"And as far as the prevalence of smoking is concerned, this means that the incidence of SAB decreases by 2.4 percent per percent of the prevalence of smoking," said the head physician of the UMM Neurosurgery department.
Of course, the parallel development of hypotension and smoking prevalence with the incidence of subarachnoid bleeding only suggests a causal relationship.
The existing data can not provide any evidence of this because quantitative data for these risk factors would be needed on the basis of the population or at the level of individual patients.
Nevertheless, the association found in the study supports preventive approaches to manage the risk factors of hypertension and smoking to reduce the risk of aneurysmal brain haemorrhage.
Reduce the risk of aneurysmal haemorrhages
At the same time, the authors are currently investigating the scientific question whether lowering blood pressure in patients with randomly detected aneurysms, which are not primarily treated but controlled by imaging, has a beneficial effect on the development of the aneurysms.
This is part of the prospective phase III study PROTECT-U (www.protect-u-trial.com/) in various neurovascular centers in Germany, the Netherlands and soon in Canada.
The current work also provides leads for further studies, the results of which, if they lead to appropriate primary prevention strategies, can help reduce the further risk of aneurysmal brain haemorrhage:
This would be a closer study of the regional differences in SAB incidence and its reduction, regional differences in age and gender related incidents, and their relation to more accurate, quantitative data on smoking behavior. (Ad)