Relationships between area deprivation and stillbirth, neonatal mortality, infant mortality, and child mortality rates in Japan from 2015 to 2022: A descriptive epidemiological study.

Abstract

Background: Evidence on the associations between area deprivation and child mortality in Japan after 2014 is limited. This study aimed to clarify the trends in stillbirth and neonatal, infant, and child mortality rates by municipal-level area deprivation index (ADI) after 2014.

Methods: We calculated the ADI for different municipalities using 2015 and 2020 Japanese census data, and applied the ADI to the analysis periods of 2015-2019 and 2020-2022. We then stratified the municipalities into quintiles by ADI, and calculated the stillbirth and neonatal, infant, and child mortality rates for each quintile from 2015 to 2022 using 3-year moving averages of data from the Vital Statistics of Japan.

Results: Throughout the study period, the stillbirth rates were higher in areas with higher ADI. The stillbirth rates decreased across all quintiles during 2019-2021 and 2020-2022, but disparities by ADI remained. For neonates, infants, and children, no clear associations were consistently observed between ADI and mortality rates until 2018-2020. From 2018-2020 onward, the mortality rates became higher in areas with higher ADI.

Conclusion: Municipal disparities in stillbirth rates according to ADI were observed throughout 2015 to 2022. In contrast, disparities in neonatal, infant, and child mortality according to ADI were not apparent from 2015 to 2019 but observed from 2020 to 2022. This period coincided with the COVID-19 pandemic period. Because this study was descriptive, the reasons for these temporal changes cannot be determined. Further studies are needed to clarify the underlying mechanisms.