Breast cancer is the most commonly diagnosed cancer among women worldwide, and its outcome depends heavily on the stage at which it is detected. Tumors identified through organized mammography programs are, on average, smaller and less advanced than those found after symptoms appear, which is why health authorities across high-income and middle-income countries have invested heavily in population-wide screening. South Korea operates one of the most comprehensive such programs, offering biennial mammography to women over designated ages through a national infrastructure administered in connection with the National Health Insurance Service. The program’s reach makes the country an unusually informative setting for studying whether organized screening delivers equitable participation.

Screening is most effective when it is repeated at regular intervals, yet most studies of screening disparities have examined only single rounds of testing. The new study takes a longer view, asking not simply whether women ever received a mammogram but whether they completed every one of the five biennial screening cycles recommended across a ten-year window. This distinction matters because organized screening programs are designed to detect tumors early through consistent, population-wide participation, and gaps in adherence can allow cancers to progress undetected between rounds. A woman who attends one appointment but misses the next three receives far less of the program’s protective benefit than the single-round statistics would suggest. Prior research has already documented that women with disabilities experience disparities not only in screening but also in cancer detection and treatment, contributing to poorer outcomes overall. The Korean team set out to quantify how disability status, disability type, and disability severity shape the odds of completing the full course of recommended screening.

To answer that question, the investigators assembled a retrospective cohort by linking two national data sources: the Korean National Cancer Screening Program Data, which records participation in the country’s organized screening services, and the Korea National Disability Registration System, which contains medically verified records of disability. The cohort comprised 4,956,744 women who participated in screening in 2011 or 2012 and were then followed for ten years. Because disability registration in Korea requires medical verification, the researchers were able to classify participants not only by whether they had a disability but also by its officially defined type and its severity. The fifteen disability types recognized under the national system were grouped into six broader categories: physical disabilities, brain injury, communication disabilities, major internal organ disabilities, intellectual disability and autism, and mental disorders.

This administrative linkage gave the study a foundation that survey-based research often lacks. Self-reported screening behavior is known to be imperfect, with respondents sometimes recalling tests that records do not confirm, and self-reported disability can be inconsistent across conditions and cultures. By drawing on government records of both screening attendance and disability status, the investigators minimized recall bias and misclassification, producing a dataset in which the exposure and the outcome were each documented independently of the participants’ own reports.

The primary outcome was deliberately stringent: completion of all five recommended biennial screening cycles over the follow-up period. This measure captures the kind of sustained, long-term engagement that screening programs depend upon, rather than a single episode of care. By anchoring the analysis in a universal, government-organized screening program, the study also offered an opportunity to examine whether disparities persist in a system where cost-related obstacles have been substantially reduced for participants, including provisions designed to ease access for people with disabilities.

The findings were unambiguous. Women with disabilities had lower odds of completing all five screenings compared with women who had no registered disability. The disparity was not uniform, however. The researchers observed a gradient pattern by severity: women with severe disabilities showed the lowest adherence, while those with mild disabilities had slightly higher adherence than their severely disabled counterparts, though the overall pattern still reflected disadvantage relative to women without disabilities. This gradient suggests that the barriers to long-term screening are not simply a binary matter of having or not having a disability, but intensify with the degree to which a disability affects daily functioning and health care access. In practical terms, the more support a woman needs to manage daily life, the less likely she was to remain within the screening program across an entire decade.

Disability type also mattered. Adherence differed across the six categories, with the lowest participation among women with intellectual disability and autism and the highest participation among women with physical disabilities. That physical disabilities were associated with comparatively better adherence, while intellectual and developmental disabilities carried the greatest disadvantage, points to barriers that extend beyond the logistical challenges of physically attending a screening appointment. Communication difficulties, differences in health literacy, caregiver dependence, and the ways screening services are designed and delivered may all play a role in shaping whether women with cognitive and developmental disabilities return for repeated mammograms over a decade. Mammography itself can be an uncomfortable and confusing procedure, and for women who have difficulty understanding explanation, consenting to the examination, or tolerating the positioning it requires, each successive appointment may become harder to arrange and complete without individually adapted support.

A central implication of the study is that financial support alone does not close the gap. Korea’s National Cancer Screening Program provides organized, population-based mammography with reduced or eliminated cost barriers, meaning that the disparities observed cannot be attributed primarily to an inability to pay. Instead, the authors argue, the persistence of these gaps points to structural and procedural obstacles embedded in how screening is offered, scheduled, communicated, and experienced by women with disabilities. The study’s conclusion calls explicitly for policy efforts such as a disability-responsive design of screening services and routine equity monitoring within organized screening programs, so that participation gaps can be tracked and addressed systematically rather than left to emerge unnoticed in aggregate statistics.

The research carries considerable weight because of its scale and design. A cohort of nearly five million women, drawn from nationwide administrative data and followed for a full decade, offers a level of statistical power and generalizability within the Korean context that smaller, clinic-based or survey-based studies cannot match. The size of the cohort also allowed the investigators to examine subgroups that smaller studies often cannot analyze reliably, including women with rarer disability types, without losing precision. The use of medically verified disability registration data also reduces the risk of misclassification that can arise when disability status is self-reported. The study was approved by the Institutional Review Board of the College of Medicine at The Catholic University of Korea, and the requirement for informed written consent was waived because the analysis used de-identified data originally collected for administrative purposes. The work was funded by the National R&D Program for Cancer Control through the National Cancer Center, supported by the Ministry of Health and Welfare, and by a National Research Foundation of Korea grant funded through the Ministry of Science and ICT.

Like all observational research, the study has limitations that shape how its findings should be interpreted. Because it relies on registered disabilities, women who have impairments but are not formally registered would be counted among those without disabilities, potentially diluting measured differences. If anything, this misclassification would tend to make the observed disparities appear smaller than they truly are, which lends additional weight to the gaps the study did detect. The cohort consists of women who participated in screening at the outset, in 2011 or 2012, which means the analysis focuses on long-term adherence among initial participants rather than on initial uptake itself; women with disabilities who never entered the program in the first place would fall outside the cohort entirely, so the full extent of screening inequity may be still greater. As with any retrospective cohort design, the study can identify associations between disability characteristics and screening adherence but cannot definitively establish the mechanisms through which those associations arise. The findings are also rooted in the specific structure of Korea’s organized screening program and disability registration system, and the degree to which they generalize to other health systems with different financing, delivery, and disability classification arrangements would require further study.

Nevertheless, the study adds an important international data point to a growing body of evidence that people with disabilities face systematic disadvantages across the cancer care continuum, from prevention and screening through diagnosis and treatment. International health frameworks have increasingly emphasized that persons with disabilities have the same right to the highest attainable standard of health as everyone else, and that health systems are obligated to remove the barriers that prevent them from exercising that right. By demonstrating that these disadvantages persist in a system with universal organized screening and reduced financial barriers, the Korean findings challenge the assumption that coverage and cost subsidies are sufficient to achieve equity. The severity gradient and the especially low adherence among women with intellectual disability and autism suggest that interventions will need to be tailored: accessible facilities and transportation support may help some women, while others may require adapted communication, longer appointments, caregiver involvement, or individualized reminder and navigation systems.

The authors’ call for disability-responsive design implies rethinking screening programs from the ground up, considering how appointment scheduling, facility layout, mammography equipment, staff training, and follow-up communication accommodate the full range of disability types and severities. Routine equity monitoring, meanwhile, would embed the kind of analysis performed in this study into the ongoing operation of screening programs, allowing administrators to detect widening gaps and evaluate whether interventions are working. As organized screening programs in many countries confront aging populations and growing attention to health equity, the Korean cohort study offers both a warning and a template: long-term adherence data, disaggregated by disability status, type, and severity, can reveal disparities that single-round participation statistics conceal, and addressing them will require deliberate design choices rather than the removal of financial barriers alone.