Impact of COVID-19 on national health screening participation and chronic disease detection: evidence from South Korea’s NHIS database

Background The COVID-19 pandemic disrupted preventive healthcare services worldwide, raising concerns about missed diagnoses of chronic diseases. South Korea’s national health screening program experienced a substantial decline in participation during 2020. This study investigated how changes in screening rates influenced chronic disease detection and what these shifts reveal about the resilience of the national health system. Methods Using the Korea Disease Control and Prevention Agency-National Health Insurance Service (K-COV-N) database, we analyzed trends in national health screening participation (2010–2020) and new diagnoses of hypertension, diabetes mellitus, and dyslipidemia before (2019) and during (2020) the COVID-19 pandemic. Analyses were stratified by sex and 10-year age groups to partially control for confounding factors. Relative risks (RRs) and 95% confidence intervals (CIs) for newly diagnosed chronic diseases were calculated for individuals who underwent health checkups and those who did not. Results Health screening participation dropped from 75.4% in 2019 to 68.7% in 2020. Despite this decrease, new diagnoses of chronic diseases increased by approximately 550,000 cases in 2020 compared with 2019. Hypertension, diabetes, and dyslipidemia all showed higher relative risks among individuals who underwent screenings than among those who did not. Cardiovascular and cerebrovascular diseases declined, while heart failure increased slightly. Conclusion The decline in preventive health screening did not correspond to a decline in chronic disease detection, suggesting a behavioral and systemic shift toward alternative diagnostic pathways. These findings underscore a resilient yet uneven health system, revealing both adaptive strengths and structural vulnerabilities that maintain continuity of essential services during public health crises.