OBJECTIVES: This study aims to comprehensively investigate the impact of COVID-19 on national mortality in South Korea.

METHODS: We conducted interrupted time series (ITS) analysis using national mortality data by cause covering the period from January 1995 to December 2021. Causes of death were categorized based on the ICD-10 classification system. Our analysis focused on deaths per month, and three key variables were considered in the ITS models: time, a COVID-19 dummy variable, and time after COVID-19. Generalized linear square models with AR1 correlation structure were employed for each cause of death.

RESULTS: Our analysis included a total of 20 ITS models, encompassing various causes of death, including all deaths. The COVID-19 dummy variable exhibited a significant positive association (p<0.001) exclusively for patients who died from "Diseases of the respiratory system (J00-J99)". Moreover, the time after COVID-19 variable demonstrated a significant positive association (p<0.01) for total deaths, "Certain infectious and parasitic diseases (A00-B99)", "Diseases of the nervous system (G00-G99)", "Diseases of the genitourinary system (N00-N99)", and "Symptoms, signs and abnormal clinical and laboratory findings, NEC (R00-R99)".

CONCLUSIONS: Our findings highlight the substantial impact of COVID-19 not only on respiratory-related diseases but also on the nervous and genitourinary systems. These effects can be attributable to both the direct consequences of the virus and the implementation of policy responses, including lockdown measures and adjustments in emergency room operations and hospitalization management. Notably, in the case of "Diseases of the genitourinary system," reduced access to healthcare and potential COVID-19 infections may have led to decreased dialysis treatments and increased the number of deaths. Our study underscores the critical importance of developing and implementing effective disease management strategies in anticipation of future pandemics.