Elsevier

Surgical Neurology

Volume 67, Issue 3, March 2007, Pages 264-272
Surgical Neurology

Vascular
The influence of barometric pressure changes and standard meteorological variables on the occurrence and clinical features of subarachnoid hemorrhage

https://doi.org/10.1016/j.surneu.2006.06.060Get rights and content

Abstract

Background

The purpose of this study was to examine a possible association between standard meteorological variables and their changes and the occurrence and clinical features of SAH.

Methods

Univariate association between the clinical/radiographic variables of patients with SAH and standard meteorological variables was evaluated. Next, a multivariate analysis was performed to find independent meteorological predictors for the occurrence of SAH by using a binary logistic regression analysis.

Results

Univariate analysis showed significant differences between bleeding days and non-bleeding days for the number of change days (maximal atmospheric difference of the day >10 hPa) (P < .001); for the maximal relative humidity (P < .05); for the maximal difference of vapor pressure of the day 24 hours before the bleeding day (P < .006) and between cluster days and noncluster days for the number of change days (P < .001); for the maximal difference of temperature of the day (P < .035); and for the maximal, minimal, and mean relative humidity (P < .027, P < .018, and P < .03, respectively). In the multivariate models, the variable “change day” (OR, 3.7; 95% CI, 1.2-11.3) and direction of the atmospheric pressure difference of the day (OR, 2.6; 95% CI, 1.8-7.8) were retained as independent predictors for the occurrence of SAH. For the variable cluster day as dependent variable, only change day was maintained in the model (OR, 6.9; 95% CI, 4.7-10.8).

Conclusions

Atmospheric pressure changes of more than 10 hPa within 24 hours are an independent predictor of clustering of patients with SAH. Hypertension is an independent risk factor for the occurrence of SAH at change day.

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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