SEASONAL FLUCTUATION IN THE INCIDENCE OF INTRACRANIAL ANEURYSM RUPTURE AND ITS RELATIONSHIP TO CHANGING CLIMATIC CONDITIONS

Seasonal and climatic variations have been linked to the occurrence of some types of cerebrovascular disease; however, the conditions that l ead to intracranial aneurysm rupture are not known. The purpose of the present study was to determine whether seasonal and climatic conditio ns are related to intracranial aneurysm rupture. Data provided by the Connecticut Health Information Management and Exchange were analyzed f or all patients with a primary diagnosis of aneurysmal subarachnoid he morrhage (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, N ational Oceanic and Atmospheric Administration, National Environmental Satellite Data, and Information Service. During the time periods stud ied, 1487 patients with a primary diagnosis of aneurysmal SAH were tre ated by reporting hospitals. Seasonal variation in the incidence of an eurysmal SAH and admission clustering were observed but differed signi ficantly 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 o ccurring in late spring (Roger's r = 10.3, p < 0.01). Substantial clim atic change occurred during the 72 hours prior to 10 of the 14 cluster s 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 flu ctuation, with women showing a different seasonal pattern from men. Ch anging climatic conditions precede aneurysm rupture in men but not in women, which suggests that weather is causally related to aneurysm rup ture in men, and that factors that lead to aneurysm rupture in women m ay be different from those in men. These data do not explain why weath er fronts or gradients are associated with aneurysm rupture in men.