July 2025
Subarachnoid haemorrhage: more than 70% of burden linked to modifiable risk factors
By Rebecca Jenkins
Age-standardised burden rates of subarachnoid haemorrhage (SAH) are decreasing, a global study finds, but the condition remains one of the most common cardiovascular (CV) and neurological causes of death and disability, with constantly increasing absolute case numbers.
Nontraumatic SAH was the third most common type of stroke with unique aetiologies, risk factors, diagnostics and treatments, researchers wrote in JAMA Neurology, but epidemiological studies often clustered SAH with other types of stroke, meaning there was some obscurity around disease burden.
For this study, researchers used the Global Burden of Disease 2021 study datasets to estimate the burden of nontraumatic SAH among people of all ages in 204 countries and territories between 1990 and 2021. They found there were 700,000 new SAH cases in 2021, almost 8 million patients with prevalent SAH, 350,000 SAH deaths, and more than 10 million SAH-related disability-adjusted life years globally.
‘This ranked SAH as the 36th most common cause of death and 59th most common cause of death and disability in the world among 300 critical health outcomes,’ the researchers wrote.
‘Although the global age-standardized mortality and DALY rates of SAH more than halved during the last three decades, the absolute number of patients with prevalent SAH increased by over 60% during the same period.’
The analysis found more than 70% of the SAH-related burden appeared to be attributed to 14 modifiable risk factors, most importantly high systolic blood pressure and smoking.
‘Given the substantial and potentially preventable impact of SAH on global health, consideration of its distinct features from other stroke types in evidence-based public health planning, resource allocation, and prevention strategies is warranted,’ the researchers concluded.
Associate Professor Cheryl Carcel, Program Head of Brain Health at The George Institute for Global Health, and Conjoint Associate Professor at the Faculty of Medicine, UNSW Sydney, said the analysis was consistent with what was known about SAH in Australia and globally.
‘As a clinician and researcher, I welcome the approach of looking at SAH separately as it has a different pathophysiological mechanism from ischaemic stroke and intracerebral haemorrhage,’ she told Medicine Today.
Professor Carcel also highlighted the importance of the study’s intersectional analysis of sex and age, noting these data can enable equity in healthcare by revealing disparities in diagnosis, treatment access or outcomes that might otherwise be missed.
‘Overall, females had higher prevalence of SAH and in high sociodemographic index regions, females had higher incidence, prevalence, mortality and disability adjusted life years,’ she said.
Given elevated systolic blood pressure and cigarette smoking were both routinely targeted in primary care as part of comprehensive CV risk management, SAH prevention was closely aligned with established CV risk-reduction strategies.
In the future, Professor Carcel said it was important to gather data on vaping and SAH risk, noting there were currently no such data.
She also noted that the study identified ambient and household air pollution as substantial contributors to SAH burden.
‘Ambient particulate matter pollution is an under-recognised risk factor for SAH and CV disease, in general, and can have public health implications,’ she said.