Elsevier

The Lancet Neurology

Volume 8, Issue 7, July 2009, Pages 635-642
The Lancet Neurology

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Changes in case fatality of aneurysmal subarachnoid haemorrhage over time, according to age, sex, and region: a meta-analysis

https://doi.org/10.1016/S1474-4422(09)70126-7Get rights and content

Summary

Background

In a systematic review, published in 1997, we found that the case fatality of aneurysmal subarachnoid haemorrhage (SAH) decreased during the period 1960–95. Because diagnostic and treatment strategies have improved and new studies from previously non-studied regions have been published since 1995, we did an updated meta-analysis to assess changes in case fatality and morbidity and differences according to age, sex, and region.

Methods

A new search of PubMed with predefined inclusion criteria for case finding and diagnosis identified reports on prospective population-based studies published between January, 1995, and July, 2007. The studies included in the previous systematic review were reassessed with the new inclusion criteria. Changes in case fatality over time and the effect of age and sex were quantified with weighted linear regression. Regional differences were analysed with linear regression analysis, and the regions of interest were subsequently defined as reference regions and compared with the other regions.

Findings

33 studies (23 of which were published in 1995 or later) were included that described 39 study periods. These studies reported on 8739 patients, of whom 7659 [88%] were reported on after 1995. 11 of the studies that were included in the previous review did not meet the current, more stringent, inclusion criteria. The mean age of patients had increased in the period 1973 to 2002 from 52 to 62 years. Case fatality varied from 8·3% to 66·7% between studies and decreased 0·8% per year (95% CI 0·2 to 1·3). The decrease was unchanged after adjustment for sex, but the decrease per year was 0·4% (−0·5 to 1·2) after adjustment for age. Case fatality was 11·8% (3·8 to 19·9) lower in Japan than it was in Europe, the USA, Australia, and New Zealand. The unadjusted decrease in case fatality excluding the data for Japan was 0·6% per year (0·0 to 1·1), a 17% decrease over the three decades. Six studies reported data on case morbidity, but these were insufficient to assess changes over time.

Interpretation

Despite an increase in the mean age of patients with SAH, case-fatality rates have decreased by 17% between 1973 and 2002 and show potentially important regional differences. This decrease coincides with the introduction of improved management strategies.

Funding

Netherlands Organisation for Scientific Research; ZonMw.

Introduction

In 1997, in a systematic review of case fatality rates reported after aneurysmal subarachnoid haemorrhage (SAH) in population-based studies published between 1965 and 1995, we found a non-significant reduction in the case fatality rate of 0·5% per year.1 Since publication of that systemic review, diagnostic and treatment strategies for SAH have advanced: the introduction of CT angiography has aided early detection of aneurysms; the use of nimodipine has been implemented at many centres after publication of a key trial in 1989;2 dedicated stroke units have been introduced;3 and endovascular coiling of ruptured aneurysms, which was introduced in the early 1990s,4 has substantially improved the prognosis of patients who reach hospital in a good or reasonably good condition and are eligible for such treatment.5

New population-based studies have been published since 1995, but whether the improved diagnostic and management strategies have led to a decrease in the case fatality of SAH in the general population is not known. Moreover, some of the new population-based studies were done in regions that were not covered in our first review. In the previous review, only a few studies included case morbidity and case fatality as outcome measurements. Because case morbidity is important, not only for the patients but also for their relatives and society in general, a more precise estimate would be useful.

We did a meta-analysis on population-based case fatality and functional outcome after SAH 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.

Section snippets

Study selection

To find new population-based studies on SAH we used the same methods as we used in the previous review.1 We did an additional PubMed search from January, 1995, to July, 2007, with different combinations of the following key words: (“subarachnoid h[a]emorrhage”) and (“epidemiology” or “population” or “mortality” or “outcome” or “case fatality”) and (“1995/1/1”; “2007/7/1”); (“stroke”) and (“epidemiology” or “population” or “mortality” or “outcome” or “case fatality”) and (“1995/1/1”; “2007/7/1”)

Results

We identified 33 articles, 23 of which were published in 1995 or later, that covered 39 study periods9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 between 1972 and 2003 (table 1).42, 43, 44 The median mid-calendar year of all studies was 1994. The studies were done in 19 countries in five continents (panel 2). Of the 21 studies that were included in the former review, 11 were excluded from the present

Discussion

Over the past three decades, case fatality rates after SAH have decreased, despite the age of the study population increasing. Because age is a predictor of poor outcome,45 we expected to find a greater decrease in case fatality after adjustment for age. However, a reduction in the point estimate for decrease in case fatality was found instead. This paradoxical finding can be explained by the inclusion of the Japanese studies in the meta-analysis.21, 24, 33 These studies were published in the

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