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

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.