Changes in mortality rate of the general population during the COVID-19 pandemic: an interrupted time series study in Korea

Background Unlike other countries, South Korea did not implement a large-scale lockdown or closure of businesses to manage the coronavirus disease 2019 (COVID-19) pandemic, but relied on changes in population behaviours and early isolation and treatment of patients. It is important to evaluate the effectiveness of such alternative strategies on the mortality of the general population. Methods Mortality and monthly population data from 2013 to 2020 were obtained. A quasi-Poisson regression model adjusting for age structure, seasonality and time was used to evaluate whether underlying trends for monthly mortality rate have changed with the pandemic. Stratification analyses based on sex and location of deaths (inside vs outside of medical facilities) were conducted. Results The risk estimates showed no changes in non-accidental mortality during the COVID-19 pandemic [relative risk (RR) (95% confidence interval, 95% CI), slope change: 1.00 (1.00, 1.01), step change: 0.99 (0.97, 1.01)] compared with those before the pandemic. In cause-specific analysis, there was an abrupt and sustained decrease in the mortality rate of respiratory diseases [RR (95% CI), step change: 0.81 (0.77, 0.84)]. In the analysis of deaths by location, an increase in non-accidental mortality [RR (95% CI), slope change: 1.01 (1.01, 1.02), step change: 1.16 (1.11, 1.22)] and several cause-specific mortalities was observed outside of medical facilities. Conclusions The non-accidental mortality rate in South Korea for the first year of the pandemic followed the historical trends. However, there was a decrease in mortality associated with respiratory diseases, and an increase in mortality occurring outside of medical facilities. The findings may be attributed to changes in public behaviours, and availability of medical resources during the pandemic.