Incidence of unruptured intracranial aneurysms: A nationwide population based longitudinal study

Background: Understanding the epidemiology of unruptured intracranial aneurysm (UIAs) is crucial for risk stratification, clinical decision making, and public health planning. The aim of this study was to perform a nationwide population-based analysis to examine the incidence of unruptured intracranial aneurysms in Sweden. Methods: Data were obtained from the Swedish National Patient Register for all persons, aged 18 years and older, diagnosed with an intracranial aneurysm (ICD-10: I67.1) between the years 2000 and 2020. Crude incidence was calculated for the total population and age- and gender-stratified groups. Age standardized incidence was assessed using the European standard population. The incidence of intracranial aneurysms diagnosed with concurrent subarachnoid hemorrhage (SAH) was also examined. Results: During the study period, 8681 patients were diagnosed with UIA. The median age of diagnosis was 63 years and 65.1% were women. The age-standardized incidence increased approximately 74% % between 2000 and its peak: from 4.6 (95% CI: 4,26-4.95) per 100,000 in the year 2000 to 7.99 (95% CI: 6.7-7.54) per 100,000 in the year 2019. The increase in incidence of UIAs was most pronounced among women and those aged above 60. During the study period, the number of cases with SAH decreased slightly. Conclusions: The increasing incidence of UIAs in Sweden might be due improved clinical detection rates, demographic changes, and changes in the prevalence of risk factors. These findings highlight the importance of enhanced surveillance, effective risk stratification, and targeted public health strategies to address the growing burden of UIAs.