Trends in hospitalizations for non-traumatic subarachnoid hemorrhage in the United States: 2012–2020

Background Although non-traumatic subarachnoid hemorrhage (SAH) remains an important cause of death and disability worldwide, contemporary research on hospitalization trends over time and across demographic groups remains scarce. Methods We performed a cross-sectional study of U.S. SAH hospitalizations from 2012 to 2020 using data from the National Inpatient Sample. SAH-related hospital discharges were identified using diagnostic codes from the International Classification of Disease , Ninth and Tenth Revisions (ICD-9/10). Incidence per 100,000 hospitalizations was calculated (2012–2020), pre- and post- the ICD-9 to ICD-10 transition (2012–2015; 2016–2020), and yearly among all hospitalizations and in subgroups defined by patient age, sex, race and ethnicity, and hospital region. Linear regression models were used to estimate change in incidence over time (separately for 2012–2015 and 2016–2020). Estimates are reported per 100,000 hospitalizations. Results From 2012 to 2020, the overall incidence of SAH hospitalization was 88.9 per 100,000 hospital discharges (95%CI = 88.6,89.3). We observed a discontinuity in incidence prior to (72.9, 95%CI = 72.5,73.5) and after (102.1, 95%CI = 101.6,102.5) the transition to ICD-10. From 2012 to 2015 the annual incidence of non-traumatic SAH hospitalization was relatively stable (3.6, 95%CI=-0.1,7.3), but higher among males, individuals of White, Black, and Asian or Pacific Islander race, and in the Midwest. From 2016 to 2020, the annual incidence of non-traumatic SAH hospitalization decreased (-2.9, 95%CI=-3.4,-2.3). This finding was largely consistent across age, sex, race or ethnicity, and region subgroups, with the largest decrease in incidence observed for aged ≥ 75 years (-8.4, 95%CI=-12.7,-4.2) and for individuals of Asian or Pacific Islander race (-11.3, 95%CI=-20.2,-2.4). Conclusions Although the incidence of non-traumatic SAH hospitalization remained stable from 2012 to 2015 and decreased from 2016 to 2020, our analysis suggests persistent differences in the risk of SAH hospitalization across subgroups defined by age, sex, and race/ethnicity.