Published 3.8.2023
Text: Ilari Rautalin
Image: iStock
Editing: Viestintätoimisto Jokiranta Oy

 

Subarachnoid haemorrhage (SAH) represents approximately 5–10 per cent of all cerebrovascular disturbances. Following cerebral infarction and intracerebral haemorrhage, SAH is the third most common cause of a stroke.

Since SAH affects healthy individuals of working age more often than other types of stroke, the related disease burden is comparable to that of other cerebrovascular disturbances. Globally, it is estimated that SAH affects about 1.2 million people each year. On average, a total of about 400,000 deaths are reported annually.

 

Healthy lifestyle plays a key role

According to several high-quality studies, SAH events are primarily caused by an unhealthy lifestyle. Smoking and high blood pressure are the most important risk factors of SAH. Other factors potentially increasing the risk of SAH include lack of physical activity, excessive alcohol consumption and high blood cholesterol.

SAH is, in a sense, a benign disease, as getting rid of unhealthy habits appears to be effective in reducing the risk of falling ill with SAH. For example, when a person quits smoking, the risk of SAH will decline to the level of non-smokers within a few years.

For decades, Finland and other Nordic countries have been at the forefront of epidemiological research on SAH, facilitated especially by the availability of nationwide register-based data of high quality. The data materials provided by the validated registers comprise thousands of patient cases. Recent reports based on these materials indicate a mainly declining trend in the incidence and mortality rates for SAH. The trend is probably attributable to the lower rates of smoking and untreated hypertension as well as advances in the diagnosis and treatment of SAH.

 

Global collaboration to reduce the disease burden

It is particularly challenging to conduct quality epidemiological research on SAH due to the fact that up to every fourth patient with SAH suffers a sudden death before receiving medical care. Thus, it is not possible to exploit hospital cohorts for the purposes of epidemiological research. Owing to the relatively low incidence of SAH, however, researchers need access to large-scale cohorts involving hundreds of thousands of individuals and long-term follow-up periods in order to obtain a sufficient number of cases for study. International collaboration should, therefore, be a rule rather than an exception in the epidemiological study of SAH.

The Sakari Alhopuro Foundation is currently supporting my work in one of the top-ranking research institutes focused on stroke epidemiology, namely the National Institute for Stroke and Applied Neurosciences in Auckland, New Zealand. During my research visit, the duration of which is 1–2 years, my intention is to explore the global disease burden of SAH, the differences across countries and the associated factors within the Global Burden of Disease (GBD) project, with epidemiological data from a total of 204 countries or regions. Another purpose of my visit is to strengthen other international collaborative projects aimed to reduce the incidence of life-threatening cerebral haemorrhage globally.

More information on subarachnoid haemorrhage (SAH) and its prevention is available online, for example, in the Terveyskylä (Health Village) portal at https://www.terveyskyla.fi/aivotalo (in Finnish and Swedish).

 

 

 

 

MD, PhD Ilari Rautalin earned his doctoral degree from the University of Helsinki in 2021. He has published several nationally and internationally acknowledged articles on SAH epidemiology in top-ranking neuroscience journals over the past years. With funding granted by the Sakari Alhopuro Foundation, Rautalin is currently working as the principal investigator for a number of international collaborative projects at the Auckland University of Technology in New Zealand.