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 greater than or equal to 80 years increased from 5% (8 patients) during 1980-1989 to 18% (33 patients) during 1990-1998 (P <0.001). The age-specific incidence rate of SAH has a tendency to increase with increasing age. The crude and the age- and sex-adjusted incidence rates using the 1995 population statistics for Japan were 21 and 23 per 100 000/y for all ages during 1980-1989 and 25 and 23 per 100 000/y during 1990-1998, respectively. The 3-month case fatality rate of patients aged less than or equal to 79 years decreased from 38% during 1980-1989 to 26% during 1990-1998 (P=0.021), whereas the case fatality rates in patients aged greater than or equal to 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 less than or equal to 79 years, the overall case fatality rate was not lower because the improvements were counterbalanced by increasing numbers of very elderly patients.