The study, an updated meta-analysis to assess changes in case fatality and morbidity and differences based on age, sex and region, shows that 8 in 100,000 people suffer from aneurysmal subarachnoid haemorrhage (SAH) each year. SAH is also responsible for between 5 and10 percent of incident stroke cases. The research also indicates that around a third of the patients die within 24 hours; over 25% of those who survive are left disabled.
Thanks to improvements in diagnosis like more advanced computed tomography (CT) and magnetic resonance imaging (MRI) techniques for detection of aneurysms, dedicated stroke units and treatments like endovascular coiling of burst aneurysms, physicians have been able to provide better prognoses for patients who are treatable.
However, it was still unclear whether these improved diagnoses, management strategies and stroke units have contributed to curbing the threat of SAH-related death or disability in the general population.
To get answers, Dr Dennis Nieuwkamp of the University Medical Centre Utrecht in the Netherlands and his colleagues conducted a meta-analysis of 33 studies involving 8,739 patients from 19 countries in 5 continents between 1973 and 2002. The results showed that the chance of dying from an SAH dropped from 51% to 35%, regardless of the fact that the average age of patients increased.
"Case fatality varied from 8.3% to 66.7% between studies and decreased 0.8% per year. The decrease was unchanged after adjustment for sex, but the decrease per year was 0.4% after adjustment for age," the study showed. "Case fatality was 11.8% lower in Japan than it was in Europe, the US, Australia and New Zealand." No other regional differences in case fatality were found.
According to the authors, disparities in how quickly patients were admitted to hospital for the early occlusion of the aneurysm could be the determining factor behind the regional differences. "In future, case fatality after SAH might decrease even more, owing to new diagnostic and therapeutic methods," the study reads. "This decrease will probably be limited to the substantial proportion of patients who die before reaching hospital or reach hospital in poor neurological condition."
"To decrease mortality from SAH, the incidence could be further reduced by prevention strategies. In future studies, meta-analysis of individual patient data would be an attractive method to get the best estimates of the rates of decline," the study concludes.
In an accompanying commentary, Drs Rustam Al-Shahi Salman and Cathie Sudlow of the University of Edinburgh in the UK said that while the reduction in case fatality after SAH is cause for optimism, two challenges remain: there is insufficient data on effectiveness of aneurysm treatment in the elderly and on how the results affect low-income to middle-income economies, as they were hardly represented in the meta-analysis.
For further information, please visit:
- The Lancet Neurology, http://www.thelancet.com/journals/laneur
- University Medical Centre Utrecht, http://www.umcutrecht.nl
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