Incidence, prevalence, and “how many are never diagnosed?”

Population imaging studies and autopsy studies both suggest that unruptured aneurysms are common, while rupture is relatively uncommon but high impact.

UIA prevalence ~3% of adults (varies by study and population)
Autopsy prevalence typically a few percent; highlights silent aneurysms
aSAH incidence ~6–9 per 100,000 person‑years globally

Unruptured intracranial aneurysm (UIA) prevalence

Systematic reviews commonly cite a prevalence around 3.2% in adults. Prevalence varies with age, sex, geography, and imaging thresholds.

  • Higher prevalence with increasing age
  • Often higher in women
  • Higher in people with smoking and hypertension
Many people with aneurysms will never know they have one, and many aneurysms will never rupture.

Aneurysmal subarachnoid hemorrhage (aSAH) incidence

Rupture causes bleeding into the subarachnoid space (aSAH). The estimated global incidence is about 7–9 per 100,000 person‑years, with regional variation (historically higher in Japan and Finland).

Even with modern care, aSAH remains a leading cause of stroke‑related death and disability in working‑age adults.

aSAH is a time‑critical emergency. Outcomes depend heavily on early recognition and rapid neurovascular treatment.

“Never diagnosed” estimate from post‑mortem findings

Autopsy studies help estimate aneurysms that were present but not diagnosed during life. Reviews of autopsy data report a wide range, often roughly 0.3%–4% for unruptured aneurysms across all ages (with variation by cohort, autopsy rate, and detection methods).

Interpretation caveats:

  • Autopsy cohorts are not always representative of the general population.
  • Small aneurysms can be missed unless careful dissection is performed.
  • Some cohorts are enriched for neurological disease or risk factors.
Practical takeaway: It is plausible that most aneurysms present in the community remain undetected simply because people are never imaged or remain asymptomatic.

Screening: who should be checked?

Routine screening of the general population is not recommended. Screening is usually reserved for higher‑risk groups (for example, strong family history, certain genetic syndromes, or prior aneurysmal SAH).

Discuss screening with a clinician if you have:

  • Two or more first‑degree relatives with intracranial aneurysm or aneurysmal SAH
  • Autosomal dominant polycystic kidney disease (ADPKD) or other relevant syndromes
  • Prior aneurysm rupture or multiple aneurysms
Search within this page
Type a word or phrase to search this page.