The Unseen Aftermath: Associations Between the COVID-19 Pandemic and Shifts in Mortality Trends in Japan

Abstract

The COVID-19 pandemic disrupted healthcare systems globally, potentially altering mortality trends for non-COVID-19 diseases, particularly in aging populations like Japan's. Assessing these impacts is essential for responsive healthcare planning. We analyzed Japanese vital registration mortality records from January 2018 to December 2021 for adults aged 25 and older, excluding COVID-19-related deaths. Data were stratified by sex and ICD-10 cause-of-death chapters. Poisson regression models assessed changes in mortality rates and trends, incorporating pandemic-related variables and interactions between time, age group, and the pandemic term. Among the 4,920,942 deaths analyzed, 2,456,750 occurred during the pandemic years. Significant sex-specific changes in mortality trends were observed. Women experienced increases in mortality rates and trends for endocrine, nutritional, and metabolic diseases; skin and subcutaneous tissue diseases; circulatory diseases; and genitourinary diseases, reversing some pre-pandemic declines. Men showed increases in mortality trends for endocrine, nutritional, and metabolic diseases and genitourinary diseases but no significant changes for skin or circulatory diseases. These findings indicate that the pandemic differentially affected mortality trends between sexes, with women experiencing broader increases across multiple disease categories. The COVID-19 pandemic was associated with significant changes in mortality trends for certain non-COVID-19 diseases in Japan, with notable sex differences. Increased mortality among women across multiple disease categories highlights the pandemic's indirect health impacts and underscores the need for sex-specific healthcare strategies in the post-pandemic era.

Keywords: COVID-19; Japan; epidemiology; gender disparities; health policy; healthcare systems; mortality trends; non-communicable diseases; pandemic; public health.

Figure 1

Mortality distribution per 100,000 by cause and sex, 2020–2021.

Figure 2

Summary of COVID-19 pandemic impact on mortality trends and levels by cause of death, sex, and age group using the Poisson model. Level changes represent immediate shifts in mortality following the pandemic onset (January 2020), where coefficients greater than 1 indicate an acute increase in average mortality, while coefficients below 1 indicate an acute decrease. Trend changes capture the long-term trajectory of mortality over time during the pandemic period, where interaction coefficients greater than 1 indicate an accelerating upward trend, and coefficients below 1 indicate a declining trend compared with pre-pandemic patterns. Level changes were assessed using the pandemic term coefficient, while trend changes were determined by the interaction between pandemic and time variables.

Figure 3

Predicted (Solid line) vs. actual death (dots) rates for: (A) metabolic disease mortality (E00–E90), (B) circulatory disease mortality (I00–I99), (C) skin disease mortality (L00–L99), and (D) genitourinary disease mortality (N00–N99) by age group and gender. The vertical dashed line marks the onset of the COVID-19 pandemic and the dotted lines represent the pre-pandemic trend. Note: The scale of the Y-axis varies between plots.