VascularThe influence of barometric pressure changes and standard meteorological variables on the occurrence and clinical features of subarachnoid hemorrhage
Introduction
Subarachnoid hemorrhage is a sudden and devastating event with a reported incidence of 6 to 16 per 100 000 inhabitants per year [4], [8], [17] and accounts for 25% of all cerebrovascular deaths. The case fatality is reported to be as high as 50% [12]. Among the remaining survivors, 50% are left severely disabled. The etiology of 80% of the cases is a ruptured intracranial aneurysm. Morbidity and mortality are largely due to rebleeding aneurysm and vasospasm [18]. Resulting from the neurosurgeon's everyday experience of a clustering of patients with SAH in times of unstable weather conditions, changing meteorological variables and even seasonal changes have been suggested to be potential risk factors. However, the influence of meteorological variables and seasonal changes on the incidence of cerebrovascular disorders including SAH is controversial, with some studies confirming a relationship [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], and others denying these findings [23], [24], [25], [26], [27].
Arising from the hypothesis that abrupt changes in weather conditions may cause an increasing rate of SAH and a clustering of patients with SAH, the aim of our study was to examine a possible association between standard meteorological variables and their changes and the occurrence and clustering of SAH in a prospective manner in a large patient group. Furthermore the association between clinical variables (Hunt and Hess grade, Fisher grade, hypertension) of patients with SAH and meteorological variables was tested.
Section snippets
Subjects
All patients referred to our department with spontaneous SAH, confirmed by CT or by lumbar puncture, between January 1, 1999, and June 4, 2005, were recruited for this study. Only patients with aneurysmal or spontaneous nonaneurysmal SAH were included. Patients with SAH due to trauma, rupture of an arteriovenous malformation, vasculitis, and other structural lesions were excluded. Only those patients were included in which the time point of the bleeding could exactly be determined in terms of
Baseline data
A total of 2347 days was evaluated, of which 465 were bleeding days and 1882 were non-bleeding days, with a total of 519 patients. Forty-three patients were excluded from the study because the exact time point of bleeding could not be determined or the SAH did not occur in our patient catchment area. Two kinds of accumulations of SAH were seen: (1) clusters of bleeding (cluster days), which was defined as an admission of 2 or more patients with SAH on the same day, and (2) bleeding series,
Discussion
During the second half of the last century, a series of articles was published concerning the association between weather conditions/seasonal climate changes and cerebrovascular disorders including SAH, with some studies supporting the occurrence of cerebrovascular disorders [21], [24], [29], [30], and some others not [20], [35]. Furthermore, reports were published concerning the association between weather conditions and an increased incidence of home deaths from cerebrovascular disease [2],
Conclusion
Atmospheric pressure changes of more than 10 hPa within 24 hours is an independent predictor of clustering of patients with SAH. Hypertension is an independent risk factor for the occurrence of SAH at change day. The exact pathophysiologic mechanism remains obscure.
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