Incidence and case fatality of aneurysmal subarachnoid hemorrhage admitted to hospital between 2008 and 2014 in Norway

Background To provide age- and sex-specific incidence and case fatality rates for non-traumatic aneurysmal subarachnoid hemorrhage (aSAH) in Norway. We also studied time trends in incidence and case fatality, as well as predictors of death following aSAH. Methods A nationwide study using discharge data for patients admitted with aSAH between 2008 and 2014. Results A total of 1732 patients with aSAH were included. The mean age was 60 years (SD 14) and 63% were females. Crude annual incidence was 5.7 per 100,000 person-years (95% CI 5.4-6.0) and was higher in females (6.3 per 100,000, 95% CI 5.9-6.7) compared with males (4.9 per 100,000, 95% CI 4.5-5.3). The annual decline in aSAH incidence was 3.2% per year (p = 0.007). The cumulative proportions of fatalities at days 30, 90, and 1 year were 22%, 25%, and 37%, respectively. The 30-day mortality rate did not change during the study period. Age (HR 0.7-2.2) and aneurysms in the posterior circulation (HR 1.7, 95% CI 1.3-2.3,p = 0.001) were associated with higher 30-day case fatality following aSAH, while aneurysm repair (HR 0.2, 95% CI 0.2-0.3,p < 0.001) was associated with lower risk. Conclusions The incidence of aSAH declined in Norway between 2008 and 2014. Case fatality following aSAH continues to be high, and the 30-day mortality during the study period was unchanged. Increasing age and aneurysms in the posterior circulation were associated with increased risk of death within 30 days following aSAH.