OBJECTIVES: Accurate capture of death data from secondary data sources in Japan is challenging as it is often limited to inpatients. The generalisability of DeSC Healthcare database to the general Japanese population in terms of demographics has already been demonstrated. We aim to describe the representativeness of death data in DeSC.

METHODS: DeSC covers insured individuals from Employee Health Insurance, National Health Insurance (NHI), and Late-Stage Elderly Health Scheme (LSEHS). Unlike other commercially available databases, DeSC captures deaths in both in/outpatient settings for NHI and LSEHS using a death flag from local governments. This study used NHI and LSEHS files from April 2014 to August 2023. Mortality rates were calculated by dividing the number of deaths by the total individuals covered, stratified by sex and age in 2022-2023. The rate was compared to the Ministry of Health, Labour and Welfare (MHLW) data for the same period.

RESULTS: Between 2014-2023, DeSC included 8,592,267 and 5,425,110 individuals in NHI and LSEHS files, with women accounting for 52.2% and 58.1%, respectively. In 2022-2023, deaths were observed in 0.6% in NHI and 5.8% in LSEHS. Mortality rates stratified by sex and age groups in NHI and LSEHS in DeSC showed similar trends to those reported by MHLW, for both sexes and all age groups. Mortality rate difference between DeSC and MHLW ranged from 0.0% for ages 0-34 years (both sexes) to 11.6% in males aged 100-104 years.

CONCLUSIONS: We demonstrated that mortality rates in NHI and LSEHS datasets in DeSC align with MHLW trends across sexes and age groups, indicating the representativeness of the DeSC’s death data compared to the overall Japanese population. The comprehensive coverage of death data suggests that DeSC’s death data are relatively reliable and can be used as a clinical outcome in real-world studies in Japan.