Prevalence of unruptured intracranial aneurysms is increasing, particularly over the past two decades, which is only in part explained by improved detection of small UIAs and an ageing population, with other factors such as environmental ones likely involved.
In a hypothetical reference population (mean age 50 years, 50% women, no comorbidities), the estimated prevalence of unruptured intracranial aneurysms (UIAs) was 3.9%.
UIA prevalence increased significantly over time, with an adjusted prevalence ratio of 1.8 for 2016–2022 versus 2002–2015 in studies of healthy individuals using MR or CT angiography.
Female sex was associated with a risk ratio of 1.9 for having a UIA compared with male sex.
Hypertension was associated with a risk ratio of 1.6 for UIA prevalence.
Current smoking was associated with a risk ratio of 1.4 for UIA prevalence.
Autosomal dominant polycystic kidney disease (ADPKD) was associated with the highest adjusted prevalence ratio among comorbidities at 4.4 compared to the reference population.
Connective-tissue disorders were associated with an adjusted prevalence ratio of 3.9 for UIA compared to the reference population.
Positive family history of aneurysmal subarachnoid haemorrhage (aSAH) or UIA was associated with a UIA prevalence of 7.9% and an adjusted PR of 2.4.
Atherosclerosis was associated with a UIA prevalence of 5.5% and an adjusted prevalence ratio of 1.3 compared to the reference population.
UIA prevalence did not differ significantly between countries.
The systematic review screened 4708 studies and included 162 articles after eligibility assessment.
This research suggests that brain aneurysms that have not yet burst (called unruptured intracranial aneurysms, or UIAs) are being found more frequently in recent years. By analyzing data from 162 studies covering more than 316,000 people, researchers estimated that approximately 1 in 25 people (about 3.9%) in a typical middle-aged population harbor a UIA. However, in studies of healthy people using modern brain imaging between 2016 and 2022, the detected prevalence was even higher—around 6.6%—and nearly double the rate seen in studies from 2002 to 2015. While better imaging technology and an older population explain some of this increase, the authors found these factors alone do not fully account for the rise, suggesting that other unknown factors, possibly environmental, may be contributing. The research also identified specific groups with substantially higher rates of UIAs. People with autosomal dominant polycystic kidney disease (a hereditary kidney condition) had about a 12.8% prevalence, and those with connective tissue disorders had about a 10.3% prevalence—both roughly 4 times higher than the reference population. A family history of brain aneurysm or related bleeding was also associated with higher prevalence. Among lifestyle and health factors, being female nearly doubled the likelihood of having a UIA compared to men, having high blood pressure increased risk by 60%, and current smoking increased risk by 40%. These findings matter because UIAs can rupture and cause a life-threatening type of stroke called subarachnoid hemorrhage. This research suggests that people in high-risk groups—particularly those with polycystic kidney disease, connective tissue disorders, or a family history of aneurysms—may benefit from personalized screening strategies. The unexplained increase in UIA prevalence over recent decades also highlights a need for further investigation into what environmental or lifestyle changes may be driving more people to develop these aneurysms.
Dremel J, Rücker V, Badel C, Ziebart A, Vlak M, Hetjens S, et al.. (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