Why Are COVID-19 Mortality Rates by Country or Region So Different?: An Ecologic Study of Factors Associated with Mortality from Novel Coronavirus Infections by Country

Abstract

Background In order to find out the factors associated with the large disparities in COVID-19 mortality rates by country, we conducted an ecological study by linking existing statistics. In Japan, a large variation was observed in between geographical areas when assessing mortality. We performed a regional correlation analysis to find factors related to regional mortality. Methods This study design was an ecologic study. A multiple regression analysis was performed with COVID-19 mortality rates of different countries as the dependent variable together with various health care and economic factors. We calculated the cumulative mortality rate as of June 30, 2020. For the regional correlation analysis of Japan, 47 prefectures were divided into nine regions. The factors examined were health care and tourism. Data for 33 Organization for Economic Cooperation and Development (OECD) countries were analyzed. In Japan's regional analysis, the whole country was classified into nine regions. Results Factors related to mor tality were the incidence of Kawasaki disease (KD), number of computed tomographies (CTs), and alcohol consumption. Mortality was low in countries with high incidence of KD and high number of CTs, as well as in countries with high alcohol consumption. In European countries, high smoking prevalence and a high Gini coefficient were positively related to high mortality. According to a regional analysis in Japan, mortality was related to proportion of population in the densely inhabited districts, the number of foreign visitors per capita, and the number of Chinese visitors per capita. Conclusion Low mortality in East Asia was associated with specific disease morbidity (KD), alcohol consumption, and CT numbers. It was suggested that the mortality gap in Japan was related to the number of foreign tourists and the proportion of population in the densely inhabited districts.

Regional Variations in Coronavirus Disease 2019 Mortality in Japan: An Ecological Study

“…In this study, a 5.5-fold difference was observed in the COVID-19 mortality index by region. Such differences have also been observed in several regions (22) , (23) , (33) , (34) . For example, a previous study in 30 European countries reported up to 185-fold regional differences in the COVID-19-related deaths among these nations (34) .…”

“…Second, the risk of death among Omicron-positive individuals is known to be age-dependent (43) ; however, in this study, age adjustment could not be performed for the COVID-19 mortality index because the ages of patients who died due to COVID-19 were not publicly available in approximately one-third of the prefectures. Third, factors such as climate and the number of international travelers to Japan are known to be related to COVID-19 mortality (33) , (44) ; however, detailed regional data on these factors were not considered in this study. Fourth, this study analyzed the seventh wave, when Omicron variant BA.5 was predominant (7) ; however, whether similar results will be obtained in future pandemics may depend on the emergence of mutant strains and regional conditions.…”

The predictability of COVID-19 mortality rates based on ex-ante economic, health and social indicators

“…10 Within Japan, a large regional disparity in COVID mortality was observed. The ratio of mortality rates in the most and least affected territorial units was 83 to 1 during the first wave of the pandemic (Osaki et al 2021).…”

Detection of outlier prefectures on the mortality due to COVID-19 in Japan

“…Previous studies tried to describe the regional differences in COVID-19 epidemiology in Japan [ 5 , 6 ]. However, the prefectural differences in terms of mortality have not been well investigated, particularly on the outliers with significantly higher or lower mortality.…”