Aneurysmal subarachnoid hemorrhage in Izumo City and Shimane Prefecture of Japan. Seasonal variation.

During the five year period from 1980 to 1984, 83 patients with aneurysmal subarachnoid hemorrhage (SAH) were hospitalized in Izumo City and 548 patients in Shimane Prefecture. The seasonal variation in the onset of aneurysmal SAH in both areas was investigated. The number of patients with aneurysmal SAH was great in January, May, October and December, while small in April, June and July. No association ·could be demonstrated between the incidence of aneurysmal SAH and the mean ambient temperature or humidity. The incidence of aneurysmal SAH in this area may therefore be slightly higher in winter, but its seasonal variation does not appear to be so evident as other types of stroke such as hypertensive intracerebral hematoma.