The research, published as an open-access article in BMC Complementary Medicine and Therapies, was conducted by a team of Korean medicine researchers led by Ji-eun Yu of Pusan National University and Yohan Choi, Hanbit Jin, Eunji Ahn and corresponding author Dongsu Kim of Dongshin University. Rather than running a clinical trial, the investigators turned to one of the most powerful tools available in Korean health research: the National Health Insurance Service National Sample Cohort, a large, de-identified database drawn from the claims records of the country’s single-payer health system. Because virtually every medical encounter in South Korea generates an insurance claim, this cohort allows researchers to track diagnoses, prescriptions and healthcare visits across millions of citizens with a completeness that few other data sources can match.

The study design was a retrospective cohort analysis. The researchers identified patients diagnosed with gastric cancer and assigned each person an index date anchored to that diagnosis. They then looked backward one year to characterize each patient’s baseline healthcare utilization, including total outpatient visits, and forward one year to measure outcomes. Patients were classified as Korean medicine users if they received outpatient Korean medicine services during the defined exposure window; everyone else was treated as a non-user. This distinction matters because Korean medicine in South Korea is not a fringe practice. It encompasses herbal medicine prescriptions, acupuncture, moxibustion and other therapies delivered by licensed practitioners in dedicated clinics, and it occupies a formal, regulated place in the national health system.

The outcomes the team examined came in two distinct forms, and that distinction turned out to be the intellectual heart of the paper. The first outcome was binary: whether a patient used any analgesics, or any opioids, at all during the follow-up year, recorded simply as yes or no. The second outcome was a count: the number of analgesic prescriptions and the number of opioid prescriptions each patient received over the same period. Separating these two measures allowed the researchers to ask two different questions. Does Korean medicine change whether a cancer patient ends up on pain medication? And does it change how much pain medication that patient receives?

To answer those questions credibly, the investigators had to confront a stubborn methodological problem that plagues nearly all observational research on complementary therapies: confounding by indication and by healthcare behavior. Patients who seek out Korean medicine are, almost by definition, different from those who do not. They tend to be heavier users of healthcare in general, they may have different symptom profiles, and they may hold different attitudes toward medication. If those differences are not accounted for, any apparent association between Korean medicine and painkiller use could simply reflect the underlying characteristics of the patients rather than any effect of the treatment itself.

The team addressed this with multivariable regression analyses that adjusted for a broad set of demographic and clinical characteristics, including measures of healthcare utilization in the year before the index date. They went further, running sensitivity analyses with stricter definitions of what counted as Korean medicine use, to test whether the results depended on how liberally the exposure was defined. They also performed stratified analyses, dividing the cohort into quartiles of total outpatient visits during the exposure window and re-examining the association within each stratum. Supplementary tables in the published article document the ATC codes used to define analgesics and opioids, the distribution of annual prescription counts, and the model-based predicted outcomes for each group, giving readers an unusually transparent view of the analytical machinery behind the headline findings.

What emerged was a nuanced and, in some ways, counterintuitive result. Korean medicine use was not significantly associated with the likelihood that a gastric cancer patient would use analgesics or opioids at all during follow-up. In other words, patients who used Korean medicine were not meaningfully more or less likely than non-users to end up taking pain medication in the first place. But when the researchers turned to the intensity of medication use, a different picture appeared. In the adjusted analyses, Korean medicine use was associated with significantly lower prescription counts for both analgesics and opioids. The association was with the volume of prescribing, not the presence of prescribing.

The authors interpret this pattern as suggesting that Korean medicine may play a complementary role in medication-based pain management, one that operates on the medication burden rather than on whether medication is used. For patients living with cancer, that distinction could carry real clinical weight. Long-term analgesic and opioid use is associated with a cascade of concerns, including adverse drug events, drug interactions with chemotherapy agents, constipation, sedation and the risk of dependence. If a complementary therapy were to reduce the number of prescriptions a patient needs over a year of care, even without eliminating the need for pain drugs entirely, it could meaningfully lighten that pharmacological load. The stratified analyses, which examined the association within quartiles of prior outpatient visit intensity, were designed in part to check whether this signal simply reflected differences in how often patients see doctors, and the sensitivity analyses using stricter exposure definitions tested the robustness of the classification itself.

At the same time, the researchers are careful about what their study can and cannot show. As a retrospective analysis of insurance claims, it captures associations, not causal effects. It cannot reveal whether patients used Korean medicine because their pain was already better controlled, whether herbal prescriptions or acupuncture directly modulated pain, or whether unmeasured differences between user and non-user groups still shaped the results. Claims data also record prescriptions, not necessarily consumption, and they cannot capture over-the-counter medication use. The authors explicitly call for further studies to confirm the findings and to elucidate the underlying mechanisms, a caution that is standard in this field but particularly warranted given the complexity of cancer pain and the heterogeneity of Korean medicine practice itself.

Nevertheless, the study adds a genuinely useful data point to an international conversation about integrative oncology and opioid stewardship. Conducted under the Declaration of Helsinki with approval from the Institutional Review Board of Dongshin University, and funded by the Korea Health Industry Development Institute through grants from the Ministry of Health and Welfare, it exemplifies the kind of large-scale, claims-based evidence that health systems with integrated traditional medicine can generate. For the growing number of gastric cancer patients who already use Korean medicine alongside conventional care, the findings suggest that such use is associated with a lighter prescription burden rather than a change in whether painkillers are used at all. For policymakers weighing how complementary therapies fit into cancer care pathways, the message is subtler: the value of traditional medicine in this context may lie not in replacing conventional analgesia, but in reducing how much of it patients ultimately need. Confirming that promise will require prospective studies, but this analysis provides a rigorous starting point built on national-scale data.

Subject of Research: The association between traditional Korean medicine use and analgesic and opioid utilization in gastric cancer patients

Article Title: Association between Korean medicine use and analgesic and opioid utilization among patients with gastric cancer

Article References: Yu, J.-E., Choi, Y., Jin, H., Ahn, E., & Kim, D. (2026). Association between Korean medicine use and analgesic and opioid utilization among patients with gastric cancer. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05583-0

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05583-0

Keywords: Korean medicine, gastric cancer, analgesics, opioids, pain management, complementary and alternative medicine, National Health Insurance Service, retrospective cohort study, prescription counts, integrative oncology, healthcare utilization, South Korea