A Population-Based Study of the Incidence and Case Fatality of Non-aneurysmal Subarachnoid Hemorrhage

Background: There is a paucity of reliable and recent data regarding epidemiology of non-aneurysmal subarachnoid hemorrhage (SAH) in population-based studies. Objectives: To determine the incidence and case fatality of non-aneurysmal SAH using a population-based design. Methods: Medical records and angiographic data of all patients from Stearns and Benton Counties, Minnesota, admitted with SAH were reviewed to identify incident case of non-aneurysmal SAH. Patients with a first-time diagnosis of non-aneurysmal SAH (based on two negative cerebral angiograms performed ≥7 days apart) between June 1st, 2012 and June 30th, 2014 were considered incident cases. We calculated the incidences of non-aneurysmal and aneurysmal SAH adjusted for age and sex based on the 2010 US census. Results: Of the 18 identified SAH among 189,093 resident populations, five were true incident cases of non-aneurysmal SAH in this population-based study. The age- and sex-adjusted incidence of non-aneurysmal SAH were 2.8 [95 % confidence interval (CI) 2.7–2·9] per 100,000 person-years which was lower than aneurysmal SAH incidence of 7.2 [95 % CI 7.1–7.4] per 100,000 person-years. The age-adjusted incidence of non-aneurysmal SAH was similar (compared with aneurysmal SAH) among men; 3.2 [95 % CI 3.1–3.3] per 100,000 person-years versus 2.2 [95 % CI 2.1–2.3] per 100,000 person-years, respectively. The age-adjusted case fatality rate at 3 months was 4.46 and 0.0 per 100,000 persons for aneurysmal and non-aneurysmal SAH, respectively. Conclusions: The incidence of non-aneurysmal SAH was higher than previously reported particularly among men.