Oceanic Meteorological Conditions Influence Incidence of Aneurysmal Subarachnoid Hemorrhage Thierry Patrice, MD, PhD, Bertrand Rozec, MD, PhD, Hubert Desal, MD, and Yvonnick Blanloeil, MD Objective: Publications concerning the weather pattern of occurrence of the sub- arachnoid hemorrhage have produced controversial results. We chose to study subarachnoid hemorrhage occurring in oceanic climate with deep variations fo- cusing on partial oxygen volume (pO2) and patient history. Methods: Seventy- one patients had been successively recruited from a single center 45 km from the Atlantic shore. Climate conditions had been analyzed from 72 hours before sub- arachnoid hemorrhage to 24 hours after. According to Dalton’s law, climate conditions influence pO2, recalculated with Dupré’s formula, and patient history analyzed and scored according to the induced oxidative stress. Results: Subarachnoid hem- orrhage risk is highest during spring and autumn, lowest between midnight and 6:00 a.m. Risk is highest after a period of atmospheric pressure higher than 1010 hPa (83%) and high pO2 and lowest for atmospheric pressure lower than 990 hPa and pO2 lower than 20.6. According to the medical history, 2 groups of patients could be identified: patients without history (22%), women (62%), high atmospheric pres- sure, and relatively lower pO2; and patients with a medical history, relatively lower atmospheric pressure, and higher pO2. Atmospheric pressure decreased signifi- cantly before disruption (994 hPa) but with a constant pO2. Subarachnoid hemorrhages during high atmospheric pressure were preceded by a decrease of pO2 despite a highly stable period of high atmospheric pressure. Discussion: Atmospheric O2 changes and the subsequent oxidative stress could be the local ultimate trigger of subarachnoid hemorrhage that could result in the “ideal” fit of patient’s health conditions with the meteorological environment. Key Words: Subarachnoid hemorrhage—weather—atmospheric pressure—atmospheric oxygen pressure— pO2—intracranial cerebral aneurysm. © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved. Introduction Spontaneous subarachnoid hemorrhages (SAHs) account for about 5% of all strokes and are a major contributor to the stroke-related loss of productive life years, have an overall mortality of 45%, and thus represent a strong economic burden. Despite intense research, causes of intracerebral aneurysms (ICAs), accounting for 85% of SAH, remain largely unknown as are causes leading to their disruption. Periodically, studies aimed at correlating me- teorological conditions, seasons, and disruptions are published 1-4 as medical doctors (MDs) in charge often have the feeling that some periods of time seem more favor- able than the others. 5 Results of such studies appear controversial and heterogeneous as they are issued from very different areas around the world having each a pre- eminent weather regimen, i.e., continental, oceanic, or subtropical. Also, large cohorts of patients for epidemio- logical survey gather patients from different areas within a country, “diluting” the potential identification of me- teorological influences. 6 On the other hand, oxidative stress, the imbalance between reactive oxygen species (ROS) pro- duction and neutralization, is often cited among causes From the Anesthesiology and Intensive Care, Laënnec Hospital, University Hospital Nantes, Nantes, France. Received January 6, 2017; accepted February 9, 2017. Address correspondence to Thierry Patrice, MD, PhD, Laboratoire de Photobiologie, Anaesthesiology and Intensive Care, Laënnec Hospital, 44093 Nantes, France. E-mail: thierry.patrice@chu-nantes.fr. 1052-3057/$ - see front matter © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2017.02.031 ARTICLE IN PRESS Journal of Stroke and Cerebrovascular Diseases, Vol. ■■, No. ■■ (■■), 2017: pp ■■–■■ 1