BACKGROUND: Cancer is the leading cause of death in South Korea, underscoring the importance of screening. Despite the implementation of the National Cancer Screening Programme, persistent socioeconomic disparities remain a public health challenge. While previous studies have examined income-related inequalities in cancer screening, education-related inequalities have received comparatively less attention, and few studies have simultaneously quantified both dimensions of socioeconomic inequality over time. We aimed to quantify the absolute and relative socioeconomic inequalities in cancer screening among Korean adults aged 40-74 years. METHODS: Using repeated cross-sectional data from the Korea National Health and Nutrition Examination Survey (2016-2024), age- and sex-adjusted Slope Index of Inequality (SII) and Relative Index of Inequality (RII) were estimated annually, with the RII estimated using modified Poisson regression with robust variance to yield prevalence-ratio-based estimates. Joinpoint regression was used to assess temporal trends, and the Wagstaff Concentration Index (C-index) decomposition was used to identify contributing factors. RESULTS: Altogether, 31,272 participants were included. Overall screening rates increased from 69.0% in 2016 to 74.6% in 2024. Pro-rich inequalities persisted throughout the study period, with positive SII values and RII values greater than 1. Education-related inequality peaked in 2018 (SII 0.21; RII 1.34) and declined in 2024 (SII 0.10; RII 1.14), with no significant trend (SII: Annual Percent Change APC -4.25%, P = 0.142; RII: APC -0.98%, P = 0.225). Income-related inequality was consistently larger than education-related inequality across all years, peaked in 2016 (SII 0.27; RII 1.47) and declined significantly (SII: APC -3.26%, P = 0.011; RII: APC -1.36%, P = 0.010). The C-index decomposition indicated that income-related inequality was associated with several observed socioeconomic and healthcare coverage factors. Non-enrolment in private health insurance was a consistent positive contributor across all years, while unemployment or economic inactivity and Medical Aid beneficiary status showed larger positive contributions during the COVID-19 pandemic period. CONCLUSION: Despite increases in overall screening uptake, socioeconomic inequalities favouring advantaged groups persisted in South Korea. The narrowing of income-based disparities is consistent with partial mitigation of financial barriers, whereas education-based disparities persisted. Achieving equitable screening will require multifaceted interventions, including sickness benefits, tailored health literacy support, and proactive community outreach.
Won et al. (Sat,) studied this question.
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