Objective: A number of publications suggest that there are seasonal influences on the incidence of subarachnoid hemorrhage (SAH). Most series agree on a peak incidence during springtime. Meteorological influences have been assumed to be obvious explanations for seasonal variations. Furthermore, the perceived clustering of the incidence of subarachnoid hemorrhage is also intuitively related to meteorological influences. The present study was initiated to determine whether specific meteorological conditions are related to the occurrence of SAH in the mild climatic zone of North Rhine Westphalia.
Methods: We retrospectively examined 183 patients (107 women and 76 men) treated at our department between January 2003 and June 2005 for SAH that had occurred within the Düsseldorf metropolitan area. We correlated the date of SAH (Day 0) and of the week preceding the incident (Days -1, -3, -5, and -7) with the meteorological key parameters from Düsseldorf International Airport. Parameters analyzed were mean daily temperature (7C), relative humidity (%), barometric pressure (hPa), and weather condition (divided into 6 groups: clear, cloudy, rain, thunderstorms, snow, and not available).
Results: A relative peak incidence of SAH was found for the month of April. In addition, a diurnal rhythm with two peaks during morning and in the evening, and a statistically significant nadir during forenoon and midday was evident (P <0.002). None of the average meteorological key parameters of the day of SAH differed from the annual average, and no general trends during the days preceding hemorrhage could be identified. Apparent clustering of the occurrence of SAH could not be related to short-term meteorological trends.
Conclusion: The results of the present study demonstrate a trend toward a seasonal distribution in the incidence of SAH with a peak during spring in the metropolitan area of Düsseldorf. Furthermore, weather variables, such as temperature, barometric pressure, and humidity, were shown to be without influence on aneurysm rupture within the patient population. Therefore, the result indicates the need to validate further parameters in detail to isolate risk circumstances to achieve a risk pattern for patients with SAH.