Abstract TP1: Changing Trends in the Epidemiology of Subarachnoid Hemorrhage: A Population-Based Study

Abstract

Background: There are conflicting data on temporal trends in subarachnoid hemorrhage (SAH) incidence and outcomes. We examined trends from 1993-2020 in a long-running population-based stroke study conducted in the Greater Cincinnati Northern Kentucky (GCNK) region. Methods: Using a well-validated approach, we ascertained all incident nontraumatic SAHs among residents of the GCNK region in the following study periods; July 1993-June 94, calendar years 1999, 2005, 2010, 2015, and 2020. Potential cases were identified by ICD codes, abstracted, and then adjudicated by physicians. Aneurysmal SAH (aSAH) was defined as those with culprit aneurysms; cases with no available vessel imaging were considered aSAH if the hemorrhage volume was “massive” or if the patient died rapidly after onset. Incidence rates were compared over time using linear regression after normalizing to 2010 census demographics. The primary outcome assessed was unadjusted 30-day Case Fatality Rate (CFR), which was available through 2015. Results: We identified 518 SAH cases, of which 372 were aSAH (71.8%). Overall SAH incidence rate was stable over time, ranging from 8-10 cases per 100,000 person-years (Figure Panel A); however, the rate of aSAH showed a statistically significant decline, going from 7.2 cases/100,000 person-years in 1993 to 5.2 cases/100,000 person-years in 2020 (trend P =0.02). There was a nonsignificant increase in nonaneurysmal SAH ( P =0.09 for trend). Overall 30-day CFR declined significantly through 2015 ( P =0.006, Figure Panel B), driven predominantly by a decline in aSAH CFR (from 39.3% to 23.7%, trend P =0.04). Conclusion: We observed a significant decline in the incidence of aSAH from 1993-2020; however, overall SAH incidence was stable in the setting of numerically more nonaneurysmal SAHs. Further study is needed to understand the causes of this trend. 30-Day CFR has significantly improved both for overall SAH and for aSAH.