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

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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 <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 ≤79 years decreased from 38% during 1980–1989 to 26% during 1990–1998 (P =0.021), whereas the case fatality rates in patients aged ≥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.

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