Fusao Ikawa1, Akio Morita2, Takeo Nakayama3, Yoshihito Goto4, Nobuyuki Sakai5, Koji Iihara6, Yoshiaki Shiokawa7, Isao Date8, Kazuhiko Nozaki9, Hiroyuki Kinouchi10, Kiyohiro Houkin11, Nobuhito Saito12, Teiji Tominaga13, Michiyasu Suzuki14, Susumu Miyamoto15, Kaoru Kurisu1, Hajime Arai16. 1. 1Department of Neurosurgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima. 2. 2Department of Neurological Surgery, Nippon Medical School Hospital, Tokyo. 3. Departments of3Health Informatics and. 4. 4Clinical Epidemiology, School of Public Health, Graduate School of Medicine, Kyoto University, Kyoto. 5. 5Department of Neurosurgery, Kobe City Medical Center General Hospital, Kobe. 6. 6Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka. 7. 7Department of Neurosurgery, Kyorin University School of Medicine, Tokyo. 8. 8Department of Neurological Surgery, Okayama University Graduate School of Medicine, Okayama. 9. 9Department of Neurosurgery, Shiga University of Medical Science, Shiga. 10. 10Department of Neurosurgery, University of Yamanashi. 11. 11Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo. 12. 12Department of Neurosurgery, The University of Tokyo. 13. 13Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai. 14. 14Department of Neurosurgery, Yamaguchi University School of Medicine, Ube. 15. 15Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto; and. 16. 16Department of Neurosurgery, Juntendo University, Tokyo, Japan.
Abstract
OBJECTIVE: Japan has been reported to have the highest (and increasing) incidence of subarachnoid hemorrhage (SAH) in the world. However, there has never been a report on the nationwide incidence rate and recent trends for SAH in Japan. In this register-based study, the authors aimed to clarify the estimated nationwide SAH incidence rate and the recent trend in SAH incidence in Japan and the reasons for any changes in this trend. METHODS: The authors compiled data from the Japanese Ministry of Health, Labour and Welfare and from the records of the Japan Neurosurgical Society. They reviewed the age-standardized nationwide SAH mortality rate, the estimated age-standardized SAH incidence rate according to the age-standardized SAH mortality rate, and the estimated crude SAH incidence rate, including the 95% confidence intervals, from 2003 to 2015. The trends in the number of treatments for unruptured and ruptured cerebral aneurysms, as well as the prevalence of hypertension, current smoking status, and use of cholesterol-lowering drugs, were assessed. The estimated treatment rate for unruptured cerebral aneurysms (UCAs) was also calculated along with the 95% confidence interval. RESULTS: The estimated age-standardized nationwide SAH incidence rate significantly declined from 31.34 cases (95% CI 31.32-31.34) to 27.63 (95% CI 27.59-27.63; decrease by 11.8%) per 100,000 person-years. This decline was based on the 2010 population as the reference from 2003 through 2015 and a case-fatality rate of SAH that was assumed to decrease by 1% annually from 44% in 2003 to 32% in 2015. According to sensitivity analysis, the change rate of the estimated age-standardized SAH incidence rate ranged from -56.69% to 23.27%, with a mean of -30.91% (SD 20.52%), and there were decline trends in 92% of all trends. The estimated nationwide crude SAH incidence rate also showed a significant decline from 23.79 (95% CI 23.78-23.79) to 20.25 (95% CI 20.24-20.25; decrease by 14.9%) per 100,000 person-years. The trend in treatment numbers for UCAs increased significantly (p < 0.0001) from 2003 through 2015; however, the estimated treatment rate for UCAs was only 0.19 (95% CI 0.19-0.20) to 0.51 (95% CI 0.50-0.51) among all UCA patients. The prevalence of hypertension (males, p = 0.0003; females, p < 0.0001) and current smoking status (males, p < 0.0001; females, p = 0.0002) declined significantly from 2003 through 2015, while the use of cholesterol-lowering drugs increased significantly (males, p < 0.0001; females, p = 0.0005) during the same period. CONCLUSIONS: The estimated nationwide SAH incidence rate in Japan was higher than rates in other countries, although it has declined recently. An improving lifestyle may have contributed to the declining rate of SAH incidence in Japan.
OBJECTIVE: Japan has been reported to have the highest (and increasing) incidence of subarachnoid hemorrhage (SAH) in the world. However, there has never been a report on the nationwide incidence rate and recent trends for SAH in Japan. In this register-based study, the authors aimed to clarify the estimated nationwide SAH incidence rate and the recent trend in SAH incidence in Japan and the reasons for any changes in this trend. METHODS: The authors compiled data from the Japanese Ministry of Health, Labour and Welfare and from the records of the Japan Neurosurgical Society. They reviewed the age-standardized nationwide SAH mortality rate, the estimated age-standardized SAH incidence rate according to the age-standardized SAH mortality rate, and the estimated crude SAH incidence rate, including the 95% confidence intervals, from 2003 to 2015. The trends in the number of treatments for unruptured and ruptured cerebral aneurysms, as well as the prevalence of hypertension, current smoking status, and use of cholesterol-lowering drugs, were assessed. The estimated treatment rate for unruptured cerebral aneurysms (UCAs) was also calculated along with the 95% confidence interval. RESULTS: The estimated age-standardized nationwide SAH incidence rate significantly declined from 31.34 cases (95% CI 31.32-31.34) to 27.63 (95% CI 27.59-27.63; decrease by 11.8%) per 100,000 person-years. This decline was based on the 2010 population as the reference from 2003 through 2015 and a case-fatality rate of SAH that was assumed to decrease by 1% annually from 44% in 2003 to 32% in 2015. According to sensitivity analysis, the change rate of the estimated age-standardized SAH incidence rate ranged from -56.69% to 23.27%, with a mean of -30.91% (SD 20.52%), and there were decline trends in 92% of all trends. The estimated nationwide crude SAH incidence rate also showed a significant decline from 23.79 (95% CI 23.78-23.79) to 20.25 (95% CI 20.24-20.25; decrease by 14.9%) per 100,000 person-years. The trend in treatment numbers for UCAs increased significantly (p < 0.0001) from 2003 through 2015; however, the estimated treatment rate for UCAs was only 0.19 (95% CI 0.19-0.20) to 0.51 (95% CI 0.50-0.51) among all UCA patients. The prevalence of hypertension (males, p = 0.0003; females, p < 0.0001) and current smoking status (males, p < 0.0001; females, p = 0.0002) declined significantly from 2003 through 2015, while the use of cholesterol-lowering drugs increased significantly (males, p < 0.0001; females, p = 0.0005) during the same period. CONCLUSIONS: The estimated nationwide SAH incidence rate in Japan was higher than rates in other countries, although it has declined recently. An improving lifestyle may have contributed to the declining rate of SAH incidence in Japan.