The Moderating Effect of Demographic and Environmental Factors in the Spread and Mortality Rate of COVID-19 during Peak and Stagnant Periods

This study explores the demographic and environmental factors affecting the spread and mortality rate of COVID-19 in countries around the world. We performed a hierarchical regression by adding interaction terms to such factors as the proportion of people aged 65 or older, the ratio of foreign migrants, the number of hospital beds available, population density, the Gini index, smoking rate among the population, mean population exposure to PM2.5 and NOx emissions in each country. We found that countries with a higher proportion of people over 65 had a higher rate of confirmed positive cases, a higher mortality rate, and a higher case fatality rate. We also found that there was a positive and significant statistical correlation between the number of foreign migrants in a country and the rate of confirmed positive COVID-19 cases and the number of deaths but an inverse relationship between this variable and the case fatality rate. We found a negative relationship between the number of hospital beds and mortality and case fatality rate while but a positive relationship between the level of nitrogen oxides in the environment and the rate of confirmed positive cases, the mortality rate, and the case fatality rate, although there was no such relationship for ultrafine dust. Overall, the variables affecting the spread and mortality of COVID-19 in June, during which it was expected there would be a lull after the virus had reached its peak in May, were similar to those affecting its spread and mortality in May, but the model’s explanatory power and significance were higher in May.