Incidence of de novo intracranial aneurysm formation in initially aneurysm-free adults

Nearly all evidence on intracranial aneurysm risk factors comes from people who already harbour an aneurysm because prevalence reflects both formation and survival to detection. The rate at which new aneurysms form in initially aneurysm-free adults has rarely been measured directly, and recent reviews have identified this incidence — and the optimal re-imaging interval — as open research priorities.

In 10 995 initially aneurysm-free Japanese adults followed by serial MR angiography for 32 941 person-years, de novo aneurysm formation occurred at 1.03 per 1000 person-years (3 year cumulative incidence, 0.28%); cumulative cigarette exposure showed a graded, dose-dependent association with formation, identified here as an exploratory secondary finding.

These findings provide a screening-based quantitative reference for re-imaging strategy in adults with a normal baseline MR angiogram and identify smoking as a modifiable risk factor at...