Analysis for Climate Factors in Onset of Spontaneous Subarachnoid Hemorrhage: A Seasonal Variation Study

ABSTRACT

PURPOSE: The aim of this study was to determine whether there are monthly and seasonal variations of incidence of subarachnoid hemorrhage (SAH) in Seoul. METHODS: We conducted a cross-sectional, retrospective study on the incidence of SAH using the National Emergency Department Information System (NEDIS) of Korea, a nationwide electronic emergency medical care database. Meteorological data (daily and monthly mean sea level air pressure, daily and monthly mean air temperature, daily temperature range) between January 2010 and December 2010 in Seoul were acquired from the Korea Meteorological Administration. The incidence of SAH in patients visiting the ED was defined as those assigned the following codes of the Korea Standard Classification of Disease, 6th Revision (KCD-6codes) I600-I609. RESULTS: The diurnal variation of the onset of SAH showed two broad peak times from 10 a.m. to 2 p.m. and from 4 p.m. to 7 p.m. There was a clear seasonal variation in the occurrence rate of SAH, which was higher in winter than in any other season. Daily temperature (mean, maximum, and minimum) and mean sea-level barometric pressure were not associated with the occurrence rates of SAH. Univariate analysis showed no significant difference between bleeding days and non-bleeding days for the number of SAH patients. In multivariate analysis, the monthly mean temperature showed significant correlation with the occurrence of SAH. CONCLUSION: This study showed seasonal variation in the onset of SAH. Conduct of further population-based study would be required in order to obtain more precise and valuable information.