Abstract
OBJECTIVES: Global data often link greater socioeconomic deprivation to higher coronavirus disease 2019 (COVID-19) mortality. However, whether decentralized governance can mitigate this disparity by enabling tailored, equitable local responses remains unclear. We assessed whether Japan's decentralized pandemic response moderated the association between area-level socioeconomic deprivation and COVID-19 mortality across municipalities. METHODS: We analyzed 20,760 COVID-19 deaths from all Japanese municipalities during 2020-2021. We computed standardized mortality ratios using national age-specific and sex-specific rates to derive expected counts. We then fit a Bayesian spatial Poisson regression model with the log of expected counts as an offset to estimate smoothed relative risks (RRs). The Area Deprivation Index (ADI) represented the primary predictor; structured and unstructured random effects captured spatial correlation and residual variability. RESULTS: Mapping of smoothed RRs, categorized into quintiles, revealed higher mortality risk in northern, central, and western municipalities, with lower risk in southern and scattered central regions. Contradicting global trends, deprivation and COVID-19 mortality demonstrated an inverse association (ADI coefficient, -0.095; 95% credible interval, -0.173 to -0.018), indicating that more deprived municipalities exhibited lower RRs for COVID-19 mortality (9.1% reduction per 1-unit increase in ADI). CONCLUSIONS: The inverse relationship between area deprivation and COVID-19 mortality in Japan contrasts with global patterns. Although Japan's decentralized health system ensured equitable access to COVID-19 treatment, lower mortality in more deprived areas likely reflects additional protective factors, including population density patterns and community-specific adaptations. These findings underscore the complex interplay between socioeconomic conditions and health outcomes during global health emergencies.