Abstract WMP92: High Nationwide Incidence and Decline Trend of Subarachnoid Hemorrhage From Register-based Study in Japan

Abstract

Background and Purpose: There has never been a report of the nationwide incidence rate and the recent trend of subarachnoid hemorrhage (SAH) in Japan. This study aimed to clarify the age-standardized nationwide incidence rate and recent trend of SAH in Japan and reasons for recent changes in this trend. Methods: We compiled data from the Japan Neurosurgical Society and records from the Ministry of Health, Labor, and Welfare in Japan. We reviewed the age-standardized mortality rate and estimated crude incidence rate of SAH including the 95% confidence interval (CI) from 2002 to 2017. The trend in treatment numbers of unruptured cerebral aneurysms (UCAs), ruptured cerebral aneurysms, the estimated treatment rate of UCAs with 95% CI, and the prevalence of hypertension, current smoking and use of cholesterol-lowering drugs were assessed. Results: Based on the 2010 population as a reference, the age-standardized nationwide SAH mortality rate significantly declined from 13.91 (95%CI:13.90-13.91) to 8.12 (8.12-8.13) by 41.7% per 100,000 person-years from 2002 through 2017. The estimated crude incidence rate of SAH excluding conservative survivors per 100,000 also showed a significant decline from 25.41 (25.40-25.42) to 21.35 (21.34-21.36) by 16.0 % and from 23.89 (23.88-23.89) to 20.05 (20.04-20.05) by 16.1% , if the in-hospital mortality was 10% and 20%, respectively. The prevalence of hypertension and current smoking declined significantly (p<0.05) and use of cholesterol-lowering drugs increased significantly (p<0.05) during the same period. Conclusions: The nationwide incidence rate of SAH in Japan was higher than in other countries. However, the declining trend of SAH was shown in this study. Improving lifestyle might contribute to reducing the incidence of SAH in Japan.