Diagnosis and treatment improvements over the past 30 years have led to a 17 percent decrease in the likelihood of death from aneurysmal subarachnoid hemorrhage (SAH) in the general population, according to a meta-analysis published online June 4 in Lancet Neurology.

In high-income countries, SAH affects eight in 100,000 people annually and causes 50 percent of incident stroke cases. The condition also is associated with a poor outcome--about 30 percent of patients die within 24 hours and of those who survive more than a quarter are left disabled.

Recent advances in diagnosis and treatments including CT and MRI techniques for detection of aneurysms, dedicated stroke units and endovascular coiling of burst aneurysms have greatly improved the prognosis of patients who reach hospital in good condition and are suitable for these treatments. However, whether these better diagnostic and management strategies have reduced the risk of death and disability from SAH in the general population is not known.

Dennis Nieuwkamp, MD, and colleagues from the University Medical Centre Utrecht, in Utrecht, Netherlands, conducted a meta-analysis of 33 studies involving 8,739 patients from 19 countries in five continents between 1973 and 2002 to assess whether case fatality had decreased, whether a more precise estimate of case morbidity could be obtained, and to report differences according to age, sex and region.

Of the 21 studies that were included in the former review, 11 were excluded from the present meta-analysis because they had a retrospective study design or reported an incidence of SAH that was less than three per 100,000, according to the authors.

Findings showed that despite an increase in the average age of patients with SAH from 52 to 62 years over three decades, the likelihood of dying from SAH has declined from 51 percent to 35 percent--a decrease of 0.6 percent per year. Adjustment for sex had no effect on the reduced risk of death, and a smaller but not statistically significant decrease was shown after adjustment for age--to 0.4 percent per year.

Interestingly, case fatality rates in Japan were 11.8 percent lower than in Europe, the United States, Australia and New Zealand. No other regional differences in case fatality were found. The authors suggested that these regional differences may be the result of variation in the speed of patients' admission to hospital for the early occlusion of the aneurysm.

"In future, case-fatality after SAH might decrease even more, owing to new diagnostic and therapeutic methods...[however the focus should also be on case-morbidity]...because of the high costs from the loss of productive life-years and the long-term care of patients with SAH, who become and remain disabled from a young age," the authors concluded.

In an accompanying commentary, Rustam Al-Shahi Salman, PhD, and Cathie Sudlow, PhD, from the University of Edinburgh in Scotland, said that despite the results, two major challenges remain--aneurysm treatment in the elderly because of the aging population and the delivery of effective interventions for SAH in low to middle income countries, which bear the greatest global burden of SAH.