Age-Period-Cohort Analysis of Suicide Mortality in Japan: A 40-Year Nationwide and Prefectural-Level Study

Introduction: Suicide remains a major public health concern in Japan. Age-period-cohort analysis can differentiate the effects of age, date, and birthyear on an outcome. This study used an age-period-cohort analysis to analyze suicide mortality in all of Japan and in the 47 prefectures. Methods: Suicide mortality data from 1980 to 2021 were from the Global Burden of Disease database. Trends in the crude and age-standardized mortality rate were analyzed using Joinpoint regression. Age-period-cohort analysis was conducted using a Poisson model. Results: The suicide rate was consistently greater in men than in women. Analysis of different age groups indicated the highest rate was in men aged >80 years, although it decreased in this group over time. The suicide rate increased in the group aged 15 to 19 years, particularly in cohorts born after 1972. A strong period effect occurred from the late 1990s to early 2000s, particularly among working-age men in their 50s and 60s. There were some disparities among prefectures, in that Akita had the highest rate and Tokyo had the lowest. Conclusions: We identified key age-period-cohort effects of suicide in Japan. Economic downturns and generational differences affected suicide risk, and adolescents and middle-aged men had high risk.