Elsevier

The Lancet Neurology

Volume 10, Issue 7, July 2011, Pages 626-636
The Lancet Neurology

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Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: a systematic review and meta-analysis

https://doi.org/10.1016/S1474-4422(11)70109-0Get rights and content

Summary

Background

Unruptured intracranial aneurysms (UIAs) are increasingly detected and are an important health-care burden. We aimed to assess the prevalence of UIAs according to family history, comorbidity, sex, age, country, and time period.

Methods

Through searches of PubMed, Embase, and Web of Science we updated our 1998 systematic review up to March, 2011. We calculated prevalences and prevalence ratios (PRs) with random-effects binomial meta-analysis. We assessed time trends with year of study as a continuous variable.

Findings

We included 68 studies, which reported on 83 study populations and 1450 UIAs in 94 912 patients from 21 countries. The overall prevalence was estimated as 3·2% (95% CI 1·9–5·2) in a population without comorbidity, with a mean age of 50 years, and consisting of 50% men. Compared with populations without the comorbidity, PRs were 6·9 (95% CI 3·5–14) for autosomal dominant polycystic kidney disease (ADPKD), 3·4 (1·9–5·9) for a positive family history of intracranial aneurysm of subarachnoid haemorrhage, 3·6 (0·4–30) for brain tumour, 2·0 (0·9–4·6) for pituitary adenoma, and 1·7 (0·9–3·0) for atherosclerosis. The PR for women compared with men was 1·61 (1·02–2·54), with a ratio of 2·2 (1·3–3·6) in study populations with a mean age of more than 50 years. Compared with patients older than 80 years, we found no differences by age, except for patients younger than 30 years (0·01, 0·00–0·12). Compared with the USA, PRs were similar for other countries, including Japan (0·8, 0·4–1·7) and Finland (1·0, 0·4–2·4). There was no statistically significant time trend.

Interpretation

The prevalence of UIAs is higher in patients with ADPKD or a positive family history of intracranial aneurysm of subarachnoid haemorrhage than in people without comorbidity. In Finland and Japan, the higher incidence of subarachnoid haemorrhage is not explained by a higher prevalence of UIAs, implicating higher risks of rupture.

Funding

Julius Centre for Health Sciences and Primary Care and Department of Neurology and Neurosurgery, University Medical Centre, Utrecht.

Introduction

Rupture of an intracranial aneurysm causes subarachnoid haemorrhage. Because such haemorrhage mostly affects relatively young people (ie, younger than 65 years) and has a high case fatality and morbidity, it is an important subtype of stroke.1 The proportion of years of potential life lost from subarachnoid haemorrhage is similar to that of ischaemic stroke and intracerebral haemorrhage,2 and a recent calculation found a total economic burden of £510 million annually for subarachnoid haemorrhage in the UK.3

The incidence of subarachnoid haemorrhage is higher in Finland and Japan than in other regions, increases with age, and is higher in women.4 These regional, sex, and age differences and the slight decline in the incidence of subarachnoid haemorrhage between 1950 and 20054 might result from differences in the prevalence of aneurysms, differences in the risk of rupture, or both.

In 1998, we published a systematic review on the prevalence of unruptured intracranial aneurysms (UIAs).5 Since then, non-invasive techniques for imaging of intracranial vessels have become increasingly available and used, which has coincided with an increase in incidental detection of aneurysms6 and the publication of many new studies on the prevalence of UIAs. We aimed to incorporate the new data into the existing pooled data to provide more accurate estimates on the prevalence of UIAs in healthy populations and in groups of people undergoing brain imaging for a specific reason. We also aimed to increase the knowledge of prevalence in sex, age, and comorbidity subgroups, and to study regional differences and time trends in the extended dataset.

Section snippets

Search strategy and selection criteria

Our search methods were similar to those in our previous review.5 We did a PubMed and Embase search to retrieve all studies on the prevalence of UIAs published before March, 2011. In brief, we used the keywords “aneurysm(s) AND (cerebral OR brain OR intracranial OR berry OR basilar OR saccular OR communicating) AND (unruptured OR incidental OR prevalence OR risk)” (see webappendix p 1). We also checked the Web of Science for articles citing our previous review and searched the personal database

Results

68 studies met our predefined inclusion criteria (table 1 and figure 1),9, 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, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76 19 studies from our previous review5 and 49 new studies. We included four case-control studies (of which one was an autopsy study),26, 58, 61, 74 63

Discussion

In our analysis, the prevalence of UIAs was influenced by the presence of polycystic disease, a positive family history, age, and sex, but not by region. The prevalence was significantly higher in patients aged 30 years or older compared with those who were younger than 30 years. Women had a higher prevalence of UIAs than men, mainly attributable to an excess in women older than 50 years. Patients with ADPKD and patients with a positive family history of intracranial aneurysm or subarachnoid

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