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Association of Socioeconomic Characteristics With Disparities in COVID-19 Outcomes in Japan

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Key Points

Question  Are the COVID-19 outcome disparities between Japanese regions associated with the socioeconomic characteristics of those regions?

Findings  In this cross-sectional study of the 47 prefectures in Japan, a higher burden of COVID-19 cases and deaths was observed in prefectures with lower household incomes; a higher proportion of the population receiving public assistance; a higher unemployment rate; higher numbers of retail, transportation and postal, and restaurant industry workers; more household crowding; and higher smoking and obesity rates.

Meaning  This study found an unequal pattern of COVID-19 outcomes that was associated with the socioeconomic circumstances in Japanese regions, suggesting that these disparities in COVID-19 outcomes are not unique to the US and Europe.

Abstract

Importance  Socioeconomic factors in the disparities in COVID-19 outcomes have been reported in studies from the US and other Western countries. However, no studies have documented national- or subnational-level outcome disparities in Asian countries.

Objective  To assess the association between regional COVID-19 outcome disparities and socioeconomic characteristics in Japan.

Design, Setting, and Participants  This cross-sectional study collected and analyzed confirmed COVID-19 cases and deaths (through February 13, 2021) as well as population and socioeconomic data in all 47 prefectures in Japan. The data sources were government surveys for which prefecture-level data were available.

Exposures  Prefectural socioeconomic characteristics included mean annual household income, Gini coefficient, proportion of the population receiving public assistance, educational attainment, unemployment rate, employment in industries with frequent close contacts with the public, household crowding, smoking rate, and obesity rate.

Main Outcomes and Measures  Rate ratios (RRs) of COVID-19 incidence and mortality by prefecture-level socioeconomic characteristics.

Results  All 47 prefectures in Japan (with a total population of 126.2 million) were included in this analysis. A total of 412 126 confirmed COVID-19 cases (326.7 per 100 000 people) and 6910 deaths (5.5 per 100 000 people) were reported as of February 13, 2021. Elevated adjusted incidence and mortality RRs of COVID-19 were observed in prefectures with the lowest household income (incidence RR: 1.45 [95% CI, 1.43-1.48] and mortality RR: 1.81 [95% CI, 1.59-2.07]); highest proportion of the population receiving public assistance (1.55 [95% CI, 1.52-1.58] and 1.51 [95% CI, 1.35-1.69]); highest unemployment rate (1.56 [95% CI, 1.53-1.59] and 1.85 [95% CI, 1.65-2.09]); highest percentage of workers in retail industry (1.36 [95% CI, 1.34-1.38] and 1.45 [95% CI, 1.31-1.61]), transportation and postal industries (1.61 [95% CI, 1.57-1.64] and 2.55 [95% CI, 2.21-2.94]), and restaurant industry (2.61 [95% CI, 2.54-2.68] and 4.17 [95% CI, 3.48-5.03]); most household crowding (1.35 [95% CI, 1.31-1.38] and 1.04 [95% CI, 0.87-1.24]); highest smoking rate (1.63 [95% CI, 1.60-1.66] and 1.54 [95% CI, 1.33-1.78]); and highest obesity rate (0.93 [95% CI, 0.91-0.95] and 1.17 [95% CI, 1.01-1.34]) compared with prefectures with the most social advantages. Among potential mediating variables, higher smoking rate (RR, 1.54; 95% CI, 1.33-1.78) and obesity rate (RR, 1.17; 95% CI, 1.01-1.34) were associated with higher mortality RRs, even after adjusting for prefecture-level covariates and other socioeconomic variables.

Conclusions and Relevance  This cross-sectional study found a pattern of socioeconomic disparities in COVID-19 outcomes in Japan that was similar to that observed in the US and Europe. National policy in Japan could consider prioritizing populations in socially disadvantaged regions in the COVID-19 response, such as vaccination planning, to address this pattern.

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Article Information

Accepted for Publication: May 11, 2021.

Published: July 14, 2021. doi:10.1001/jamanetworkopen.2021.17060

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Yoshikawa Y et al. JAMA Network Open.

Corresponding Author: Yuki Yoshikawa, MD, MPH, Department of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA 02115 (yyoshikawa@hsph.harvard.edu).

Author Contributions: Dr Yoshikawa had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: All authors.

Acquisition, analysis, or interpretation of data: Yoshikawa.

Drafting of the manuscript: All authors.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Yoshikawa.

Supervision: Kawachi.

Conflict of Interest Disclosures: None reported.

Additional Contributions: We thank the health care workers, public health officials, and all other essential workers for fighting the COVID-19 pandemic.

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