Seasonal fluctuation in the incidence of intracranial aneurysm rupture and its relationship to changing climatic conditions

Abstract

Seasonal and climatic variations have been linked to the occurrence of some types of cerebrovascular disease; however, the conditions that lead to intracranial aneurysm rupture are not known. The purpose of the present study was to determine whether seasonal and climatic conditions are related to intracranial aneurysm rupture. Data provided by the Connecticut Health Information Management and Exchange were analyzed for all patients with a primary diagnosis of aneurysmal subarachnoid hemorrhage (SAH) for the fiscal years 1981, 1983, 1985, 1987, 1988, and 1989. Patient records were correlated with climatic conditions for the years 1981 to 1989 obtained from the National Climatic Data Center, National Oceanic and Atmospheric Administration, National Environmental Satellite Data, and Information Service. During the time periods studied, 1487 patients with a primary diagnosis of aneurysmal SAH were treated by reporting hospitals. Seasonal variation in the incidence of aneurysmal SAH and admission clustering were observed but differed significantly between men and women. Men showed a single large peak in late fall (Roger's r = 11.5, p < 0.005), whereas women had an annual peak occurring in late spring (Roger's r = 10.3, p < 0.01). Substantial climatic change occurred during the 72 hours prior to 10 of the 14 clusters of men who were admitted (p < 0.01, Yates' corrected chi-square 7.33, df = 1). In contrast, clusters of women admitted were not related to preceding climatic change (p > 0.25, Yates' corrected chi-square 0.06, df = 1). Hospital admissions for aneurysmal SAH display seasonal fluctuation, with women showing a different seasonal pattern from men. Changing climatic conditions precede aneurysm rupture in men but not in women, which suggests that weather is causally related to aneurysm rupture in men, and that factors that lead to aneurysm rupture in women may be different from those in men. These data do not explain why weather fronts or gradients are associated with aneurysm rupture in men.

Differential Effects of Activity and Climate on Onset of Subarachnoid Hemorrhage.

“…7) The occurrence of SAH may be associated with larger change of atmospheric temperature or pressure. 2,7,11) In our study as well, decreases in mean and minimum temperature and mean vapor pressure from the previous day were significantly higher on the days with onset than the days without onset (Table 4). Thus, a larger change of those meteorological factors may underlie the prevalence of SAH in spring and fall, although we did not find any trend showing that the mean value of these factors for 10 years were larger in spring and fall (data not shown).…”

“…The peaks of onset in males and females were in early spring and late fall, respectively, in contrast to the result reported from Connecticut. 2) These trends in males and females were not statistically significant. K. Kawai et al…”

“…Other studies found that lower global solar radiation, lower sunshine hours, decrease in mean and minimum temperature from the previous day, and decrease in mean vapor pressure from the previous day were significantly associated with SAH. 2,7,11,13) How these meteorological factors affect biological factors, and which biological factors lead to aneurysmal rupture are unclear. Low temperature is known to increase blood pressure 2,4) but lower temperature is not always associated with onset of SAH.…”

“…Seasonal variation and meteorological association of stroke has long been controversial, but only a small number of studies have focused specifically on SAH, so whether such epidemiological phenomena exist has not been determined. Statistically significant seasonal or circannual cyclic trends have been reported [2][3][4]7,12,13,19,26,27) and some meteorological factors were significantly associated with the occurrence of SAH. 2,4,7,13,15) However, other studies have not found significant seasonal variation or meteorological association.…”

“…Statistically significant seasonal or circannual cyclic trends have been reported [2][3][4]7,12,13,19,26,27) and some meteorological factors were significantly associated with the occurrence of SAH. 2,4,7,13,15) However, other studies have not found significant seasonal variation or meteorological association. 1,10,14,[22][23][24] Interpretation of such results is complicated by the multiple factors associated with the design of each study, including the number of patients studied, criteria for patient selection (based on onset, admission, surgical treatment, or death), method of sampling (community-based or hospital-based), and the statistical method used for the analysis.…”