title: Intracranial aneurysm rupture is predicted by measures of solar activity.
abstract: The cause precipitating intracranial aneurysm rupture remains unknown in many cases. It has been observed that aneurysm ruptures are clustered in time, but the trigger mechanism remains obscure. Because solar activity has been associated with cardiovascular mortality and morbidity, we decided to study its association to aneurysm rupture in the Swiss population.
  
  
  
  Patient data were extracted from the Swiss SOS database, at time of analysis covering 918 consecutive patients with angiography-proven aneurysmal subarachnoid hemorrhage treated at 7 Swiss neurovascular centers between January 1, 2009, and December 31, 2011. The daily rupture frequency (RF) was correlated to the absolute amount and the change in various parameters of interest representing continuous measurements of solar activity (radioflux [F10.7 index], solar proton flux, solar flare occurrence, planetary K-index/planetary A-index, Space Environment Services Center [SESC] sunspot number and sunspot area) using Poisson regression analysis.
  
  
  
  During the period of interest, there were 517 days without recorded aneurysm rupture. There were 398, 139, 27, 12, 1, and 1 days with 1, 2, 3, 4, 5, and 6 ruptures per day. Poisson regression analysis demonstrated a significant correlation of F10.7 index and RF (incidence rate ratio [IRR] = 1.006303; standard error (SE) 0.0013201; 95% confidence interval (CI) 1.003719-1.008894; P < 0.001), according to which every 1-unit increase of the F10.7 index increased the count for an aneurysm to rupture by 0.63%. A likewise statistically significant relationship of both the SESC sunspot number (IRR 1.003413; SE 0.0007913; 95% CI 1.001864-1.004965; P < 0.001) and the sunspot area (IRR 1.000419; SE 0.0000866; 95% CI 1.000249-1.000589; P < 0.001) emerged. All other variables analyzed showed no significant correlation with RF.
  
  
  
  We found greater radioflux, SESC sunspot number, and sunspot area to be associated with an increased count of aneurysm rupture. The clinical meaningfulness of this statistical association must be interpreted carefully and future studies are warranted to rule out a type-1 error.
authors.affiliation: Department of Neurosurgery, Kantonsspital St. Gallen, St. Gallen, Switzerland; Department of Neurosurgery, University Clinic Geneva, Geneva, Switzerland. Electronic address: mnstienen@gmail.com.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Stienen
authors.affiliation: Gippsland Medical School, Monash University, Melbourne, Australia; Department of Surgery, Frankston Hospital, Melbourne, Australia.
authors.forename: Nicolas R
authors.initials: NR
authors.lastname: Smoll
authors.affiliation: Fachhochschule Nordwestschweiz FHNW, Hochschule für Technik, Institut für 4D-Technologien, Windisch, Switzerland.
authors.forename: Marina
authors.initials: M
authors.lastname: Battaglia
authors.affiliation: Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland; Department of Neurosurgery, Georg-August-University of Göttingen, Göttingen, Germany.
authors.forename: Bawarjan
authors.initials: B
authors.lastname: Schatlo
authors.affiliation: Department of Neurosurgery, University Hospital Zürich, Zurich, Switzerland.
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Woernle
authors.affiliation: Department of Neurosurgery, Inselspital Bern, Bern, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Fung
authors.affiliation: Department of Neurosurgery, University Clinic Basel, Basel, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Roethlisberger
authors.affiliation: Department of Neurosurgery, CHUV, Lausanne, Switzerland.
authors.forename: Roy Thomas
authors.initials: RT
authors.lastname: Daniel
authors.affiliation: Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: Ali-Reza
authors.initials: AR
authors.lastname: Fathi
authors.affiliation: Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: Javier
authors.initials: J
authors.lastname: Fandino
authors.affiliation: Department of Neurosurgery, Kantonsspital St. Gallen, St. Gallen, Switzerland.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hildebrandt
authors.affiliation: Department of Neurosurgery, University Clinic Geneva, Geneva, Switzerland.
authors.forename: Karl
authors.initials: K
authors.lastname: Schaller
authors.affiliation: Department of Neurosurgery, University Clinic Geneva, Geneva, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bijlenga
mesh_terms: D017542:Aneurysm, Ruptured / Q000150:complications* / Q000453:epidemiology*; D016001:Confidence Intervals; D016208:Databases, Factual; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications* / Q000453:epidemiology*; D008297:Male; D016012:Poisson Distribution; D012044:Regression Analysis; D019445:Solar Activity; D013557:Switzerland / Q000453:epidemiology
keywords: Aneurysmal subarachnoid hemorrhage; Geomagnetic energy; Intracranial aneurysm; Rupture risk; Solar activity; Temporal clustering