Subarachnoid Hemorrhage in Germany Between 2010 and 2013: Estimated Incidence Rates Based on a Nationwide Hospital Discharge Registry.

BACKGROUND: Nordic countries are the primary source for nationwide data on the incidence of subarachnoid hemorrhage (SAH). Reliable estimates of national incidence rates of SAH in other countries are lacking, yet studies from Nordic countries with exceptional incidence rates are sometimes disregarded because of concerns regarding external validity. Autopsies are rarely performed for sudden deaths; therefore, estimates of the SAH incidence commonly reflect the hospital discharge rates. Our aim was to estimate the nationwide incidence of nontraumatic SAH in Germany using a national hospital discharge register.

METHODS: The German federal statistical office provided the number of patients discharged from all German hospitals between 2010 and 2013 with the primary diagnosis of nontraumatic SAH (ICD code I60.0-I60.9) and corresponding age distribution. Age-standardized attack rates of nontraumatic SAH were calculated using the 2011 German demographic distribution.

RESULTS: Between 2010 and 2013, the overall age-standardized incidence rate of nontraumatic SAH was 11.3 per 100,000 person-years, and it reached a maximum of 22.1 per 100,000 person-years in the oldest age group. The absolute number of SAHs was highest in the 50-55-year age group. The distribution of intracranial aneurysms displayed a propensity toward the posterior circulation with advancing age (P < 0.001), although in absolute numbers SAH originated mostly from the anterior circulation.

CONCLUSIONS: Our estimate of the German nationwide attack rate suggests that the incidence of nontraumatic SAH is more homogeneous than previously assumed. Rejecting the external validity of studies from countries believed to display an exceptional incidence rates may therefore not be justified.