Brain Aneurysms May Be Twice as Common as Previously Thought

UNRUPTURED brain aneurysms may be considerably more common than previously thought, with their prevalence more than doubling over the past two decades, according to the largest analysis of its kind.

The systematic review and meta-analysis found that the prevalence of unruptured intracranial aneurysms amongst otherwise healthy adults increased from 2.9% in studies conducted between 2002–2015 to 6.6% between 2016–2022. This suggests that approximately one in 15 healthy adults may now be found to have an aneurysm.

How Common Are Brain Aneurysms?

An intracranial aneurysm is a weakened area of a blood vessel in the brain that bulges outwards. Most remain unruptured and cause no symptoms, but rupture can result in a subarachnoid haemorrhage, a severe and potentially fatal form of stroke.

Previous estimates of the prevalence of unruptured intracranial aneurysms were largely based on research conducted more than a decade ago. Researchers therefore sought to provide updated estimates and determine how prevalence varies according to patient characteristics, underlying conditions, and established risk factors.

The systematic review and meta-analysis included 162 studies published between 1955–2025, encompassing 316,131 people. Overall, 11,822 participants were found to have at least one unruptured intracranial aneurysm.

The researchers examined prevalence across healthy populations and groups with medical conditions associated with increased aneurysm risk.

Prevalence Has More Than Doubled

Amongst healthy adults assessed using modern vascular imaging, the prevalence of unruptured intracranial aneurysms increased from 2.9% in studies conducted between 2002–2015 to 6.6% in studies from 2016–2022.

Improved imaging technology and an ageing population could contribute to more aneurysms being detected. However, the researchers reported that these factors did not fully explain the increase.

Several groups were substantially more likely to have an aneurysm. Women had almost twice the prevalence observed amongst men, while rates were particularly high amongst people with certain underlying conditions or a family history of subarachnoid haemorrhage.

The highest prevalence was identified amongst people with autosomal dominant polycystic kidney disease, a genetic condition characterised by the development of cysts in the kidneys and other organs. Increased prevalence was also observed amongst people with connective tissue disorders.

Smoking and high blood pressure were both associated with a higher prevalence of intracranial aneurysms, reinforcing the importance of potentially modifiable vascular risk factors.

Does Greater Detection Mean More Treatment?

Despite the higher prevalence, the findings do not mean that one in 15 adults requires treatment for a brain aneurysm.

Most unruptured aneurysms never rupture, meaning the potential benefit of preventive intervention must be carefully balanced against the risks associated with treatment.

The increase in detection therefore presents an important clinical challenge. As brain imaging becomes more common and increasingly sensitive, clinicians are likely to encounter more incidental aneurysms in people undergoing scans for unrelated reasons.

Determining an individual’s rupture risk is consequently more important than the presence of an aneurysm alone. Factors including aneurysm size and location, age, smoking, blood pressure, family history, and other medical conditions can all inform clinical management.

The researchers also caution that increasing prevalence across studies does not necessarily mean that the true biological occurrence of aneurysms has doubled. Changes in imaging, study populations, and detection practices over time could have contributed to the observed trend.

Nevertheless, the findings provide the most comprehensive contemporary estimate of unruptured intracranial aneurysm prevalence to date and highlight the importance of individualised risk assessment as increasing numbers of aneurysms are detected.

Reference

Dremel J et al. Prevalence of unruptured intracranial aneurysms according to comorbidities, risk factors, country, and time period: a systematic review and meta-analysis. Lancet Neurol. 2026. DOI: 10.1016/S1474-4422(26)00276-0.

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