Suicide and ill-defined/undetermined deaths in urban areas in Japan: a national database study, 2008–2022

Abstract

Background

Suicide deaths are defined as deaths due to “intentional self-harm” in accordance with the International Statistical Classification of Diseases and Related Health Problems 10th Revision. However, “ill-defined and unknown causes of mortality,” “accidents,” and “event of undetermined intent” may also account for hidden suicides. This study compared the state of deaths due to suicide and ill-defined/undetermined causes across urban areas in Japan over the past 15 years using vital statistics.

Methods

We analyzed vital statistics data including information on all deaths identified under suicide and ill-defined/undetermined death category among Japanese citizens aged ≥10 years who lived in a government ordinance-designated city between 2008 and 2022. Standardized mortality ratios (SMRs) were calculated for each cause of death and compared among designated cities.

Results

Mortality rates due to “intentional self-harm” for those aged ≥65 years decreased during the study period, whereas mortality rates due to “ill-defined and unknown causes of mortality” for those aged ≥65 years sharply increased by nearly three times. Substantial differences in SMRs for “ill-defined and unknown causes of mortality” were observed among designated cities. There was no significant change in SMRs between the pre- and peri-COVID-19 pandemic periods in each designated city.

Conclusions

In Japan, the state of deaths due to “ill-defined and unknown causes of mortality” substantially differed among designated cities. Attention must be paid to changes in the state of deaths due to ill-defined/undetermined causes as well as suicide deaths.