Rising Prevalence of Unruptured Brain Aneurysms Raises Concerns: Lancet
Germany: A systematic review and meta-analysis has found that the prevalence of unruptured brain aneurysms increased from 2.9% to 6.6% over the past two decades. This rise was only partly explained by population aging and improved imaging, suggesting that other unidentified risk factors may be contributing. Researchers recommend targeted screening for high-risk individuals rather than routine screening of the general healthy population.
Published in The Lancet Neurology, the study was led by Judith Dremel, DrMed, Department of Neurosurgery, Medical Faculty Mannheim, University of Heidelberg, Germany, and colleagues. The researchers investigated whether changes in unruptured intracranial aneurysm (UIA) prevalence mirrored the decline in aneurysmal subarachnoid haemorrhage (aSAH) seen between 1980 and 2010, a period that also saw reductions in smoking and hypertension.
The investigators searched Embase, PubMed, and Web of Science for studies published between January 2011 and December 2025 and reassessed 68 studies from an earlier systematic review. Overall, 162 studies involving 316,131 participants and 11,822 individuals with UIAs were included.
Among a hypothetical reference population with a mean age of 50 years, 50% women, and no comorbidities, the estimated prevalence of UIAs was 3.9%.
Several conditions and risk factors were associated with a greater prevalence:
- Individuals with atherosclerosis had a UIA prevalence of 5.5%, with an adjusted prevalence ratio of 1.3 compared with the reference population.
- Those with a positive family history of aSAH or UIA had a prevalence of 7.9%, with an adjusted prevalence ratio of 2.4.
- Patients with connective-tissue disorders had a prevalence of 10.3%, corresponding to an adjusted prevalence ratio of 3.9.
- Individuals with autosomal dominant polycystic kidney disease (ADPKD) had the highest prevalence among the evaluated comorbidities at 12.8%, with an adjusted prevalence ratio of 4.4.
- Current smoking was associated with a 1.4-fold higher risk, while hypertension was associated with a 1.6-fold higher risk.
- Women had a 1.9-fold higher risk of UIAs than men.
The prevalence of UIAs among healthy individuals undergoing MR or CT angiography increased from 5.0% in 2002–2015 to 6.6% in 2016–2022, with an adjusted prevalence ratio of 1.8. Aneurysms measuring ≥5 mm doubled from 0.7% to 1.4%. Prevalence was similar across countries, although considerable variation was seen between studies, and the certainty of evidence ranged from very low to moderate.
The increase could not be fully explained by improved detection of small aneurysms or population aging, suggesting that environmental or other unidentified factors may also play a role. The study was limited by its reliance mainly on selected cohorts and cross-sectional studies, while findings on connective-tissue disorders may not apply uniformly across all disorders.
The researchers called for further evaluation of personalized screening and management for high-risk groups, particularly individuals with ADPKD, a family history of aSAH, or connective-tissue disorders.
Reference:
Dremel, J., Rücker, V., Badel, C., Ziebart, A., Vlak, M., Hetjens, S., Abdulazim, A., Jírů-Hillmann, S., Heuschmann, P., Rinkel, G. J. E., & Etminan, N. (2026). Prevalence of unruptured intracranial aneurysms according to comorbidities, risk factors, country, and time period: A systematic review and meta-analysis. The Lancet Neurology. https://doi.org/10.1016/S1474-4422(26)00276-0
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