Trends in Incidence and Case Fatality Rates of Aneurysmal Subarachnoid Hemorrhage in Izumo City, Japan, Between 1980–1989 and 1990–1998

BACKGROUND AND PURPOSE: With aging of the population, the profile of subarachnoid hemorrhage (SAH) is likely to change; however, evaluation of long-term trends for incidence and case fatality rates of SAH is still limited. METHODS: We compared the incidence and case fatality rates of aneurysmal SAH during the 9-year period 1990-1998 with those during the 10-year period 1980-1989 in Izumo City, Japan. RESULTS: During 1980-1989 and 1990-1998, we diagnosed 170 and 188 patients as having aneurysmal SAH, respectively. The percentage of very elderly patients aged >/=80 years increased from 5% (8 patients) during 1980-1989 to 18% (33 patients) during 1990-1998 (P/=80 years were very high (63% and 79%, respectively) regardless of study periods. Consequently, the overall case fatality rates for patients with SAH were similar for the 2 study periods (39% and 36%). CONCLUSIONS: The age- and sex-adjusted incidence rates of aneurysmal SAH were stable over the 19-year period since 1980 and, despite improvement of outcome in patients aged </=79 years, the overall case fatality rate was not lower because the improvements were counterbalanced by increasing numbers of very elderly patients