Epidemiology of subarachnoid hemorrhage in the Yaeyama Islands, an isolated subtropical region of Japan most frequently affected by typhoons: A population-based study

ObjectiveThe present study analyzed epidemiological data for patients with subarachnoid hemorrhage (SAH) in a subtropical region of Japan that is the most frequently affected by typhoons.Patients and methodsThe medical records of hospitalized patients who had been diagnosed as having SAH at Okinawa Prefectural Yaeyama Hospital during a 13-year period were reviewed. Demographic and epidemiological data including date and time of onset and activity at onset and clinical data were collected. Meteorological data for typhoon's approaches to the Yaeyama Islands were obtained from the web-site of the Japan Meteorological Agency. In addition, patients who had developed SAH during a period of 3 days before and after the closest approach of a typhoon (CAT) were examined.ResultsA total of 94 patients were identified. A monthly peak in August, a weekly peak on Monday, and two daily peaks in the evening and morning were observed. The incidence of SAH during a period of 3 days before and after the CAT was approximately twice as high as that on other days, and a statistically significant difference was found.ConclusionPeriodic patterns of SAH onset revealed unusual monthly and circaseptan variations and the usual circadian variation. SAH onset was associated with typhoon's approaches.