Long-Term Trends in The 5-Year Risk of Recurrent Stroke over A Half Century in A Japanese Community: The Hisayama Study

Aim: Secular trends in the risk of recurrent stroke have been reported in several epidemiological studies worldwide, but this issue has not been investigated in general Japanese populations. We examined the trends in the 5-year risk of recurrent stroke over a half century using community-based prospective data in Japan. Methods: We established 4 cohort studies in 1961, 1974, 1988, and 2002. To examine the risk of recurrent stroke, participants who developed stroke during a 10-year follow-up period in each cohort were followed-up for 5 years from the date of first onset. A total of 154 (first sub-cohort: 1961-1971), 144 (second sub-cohort: 1974-1984), 172 (third sub-cohort: 1988-1998), and 146 (fourth sub-cohort: 2002-2012) participants from each cohort were enrolled in the present study. The 5-year cumulative risk of recurrent stroke was compared among the sub-cohorts using the Kaplan-Meier method and the age-and sex-adjusted Cox proportional hazards model. Results: The risks of recurrent stroke after any stroke and ischemic stroke decreased significantly from the first to the third sub-cohort, but they did not clearly change from the third to the fourth sub-cohort. The risk of recurrent stroke after hemorrhagic stroke decreased mainly from the first to the second sub-cohort and there was no apparent decrease from the second to the fourth sub-cohort. These trends were substantially unchanged after adjusting for age and sex. Conclusions: In the Japanese community, the risk of recurrent stroke decreased mainly from the 1960s to 1990s, but there was no apparent decrease in recent years.