Pnd8 incidence rates of subarachnoid hemorrhage in patients with unruptured aneurysm in south korea from 2006-2009

To investigate the incidence of subarachnoid hemorrhage(SAH) in patients with unruptured intracranial aneurysm(UIA) in South Korea from 2006-2009. A longitudinal study using national representative health claim database including all hospital records for every Korean citizen was employed. We identified patients with UIA who were 18-80 years old using ICD-10 codes of I67.1 in 2006. To select eligible patients, history period was applied for one year from first diagnosis of UIA (i.e. index date) in 2006. We excluded patients with UIA diagnosis, SAH, or treatments(clip and coil) during history periods. Patients with head trauma or brain tumor during study periods were also excluded. Eligible patients were followed for at least 3 years from index date. SAH patients were defined as ICD-10 codes of I60 excluding I60.8 with the hospitalization of >=14days or death within 14days from hospitalization. Sensitivity analysis was conducted to see the robustness using different definition of SAH. Additionally, the length of stay of SAH was estimated using generalized linear model with log link and gamma distribution. We identified 7404 eligible patients with UIA, including 1,466(20%) treated patients and 5,938(80%) untreated patients for median follow-up of 3.4 years. For patients with untreated UIA, the incidence rate of SAH was 0.7/100person-years(PYs) (133/5,934 patients). In the definition of SAH of all hospitalization, the incidence rate increased by 1.3/100PYs. The incidence of SAH was highest in the first year after first diagnosis of UIA. Mean length of stay of SAH was 30days(95%CI:24.0-36.2) for males and 38days(95%CI:32.8-42.8) for females, respectively. The rupture rate for untreated UIA patients were 0.7-1.3/100 PY from 2006-2009. This study results indicate that careful follow-up for UIA patients is needed to prevent rupture and decrease economic burden of SAH.