Oceanic Meteorological Conditions Influence Incidence of Aneurysmal Subarachnoid Hemorrhage.

OBJECTIVE: Publications concerning the weather pattern of occurrence of the subarachnoid hemorrhage have produced controversial results. We chose to study subarachnoid hemorrhage occurring in oceanic climate with deep variations focusing 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 subarachnoid 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 hemorrhage 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 pressure, and relatively lower pO2 ; and patients with a medical history, relatively lower atmospheric pressure, and higher pO2 . Atmospheric pressure decreased significantly 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.