Epidemiology of Subarachnoid Hemorrhage in the Yaeyama Islands, an Isolated Subtropical Region of Japan

Abstract

Epidemiological studies of periodicity, clustering, and meteorological association in relation to the onset of subarachnoid hemorrhage (SAH) have already been reported for populations in the temperate and subarctic latitudes. The purpose of the present study was to analyze epidemiological, especially environmental data for patients with SAH in the Yaeyama Islands, an isolated subtropical region of Japan. A total of 94 patients (31 males and 63 females, mean age 57.3 years) were diagnosed as having SAH during a 13-year period from 1989 to 2002. The age- and sex-adjusted annual incidence rate of SAH was 17.4 per 100,000 person-years. In comparison with other Japanese studies, the present demographic data indicated a stronger predominance of females, a relative younger age at onset, and an average annual incidence rate. Periodic patterns of SAH onset showed a seasonal peak in fall, a monthly peak in August, a weekly peak on Monday, a daily large peak in the evening, a daily small peak in the morning, and a daily trough in the period from midnight to dawn. The incidence of SAH for the 3 days before and after the day when a typhoon went nearest within 300km from the Ishigaki Island was about 1.8 times as high as but those days. SAH occurred more frequently during daily living or labor activities. Periodicity in the onset of SAH and its association with the approach of typhoons were demonstrated more clearly in patients with no or light stress at onset.