Association between self-purchased medication use and gastric disease among Chinese adults: a cross-sectional analysis based on CHARLS 2018 data

BACKGROUND: Gastric diseases are a major health burden, especially in East Asia, with high incidence and mortality rates. While Helicobacter pylori infection and poor lifestyle behaviors are established risk factors, the impact of drug-related gastric injury in aging populations remains underexplored. In China, polypharmacy is common among older adults, with nearly 40% using self-purchased medications without professional guidance. Similar trends are observed in other aging societies, highlighting the global challenge of unregulated drug use. Existing studies lack adjustments for comorbidities, prediction tools, and methodological innovation. This study analyzes CHARLS 2018 data to: (1) examine the relationship between self-purchased medication use and gastric disease, and (2) identified strongly associated groups, such as patients with chronic kidney disease (CKD) and diabetes. METHODS: We included 19,752 participants from the CHARLS database. Participants were divided into gastric disease and control groups based on DA007_10 questionnaires. We compared baseline characteristics, including self-purchased medication use, between groups. Multivariate logistic regression models were used to assess the correlation between self-purchased medication use and gastric disease. The receiver operating characteristic (ROC) curve evaluated Model 3's predictive performance. Stratified analysis was conducted to assess the stability of the results. RESULTS: Significant differences were observed between the gastric disease (n = 659) and control (n = 5,428) groups in factors such as ethnicity, self-reported health status, hypertension, dyslipidemia, diabetes, chronic lung diseases, liver disease, kidney disease, smoking history, and medication use. In all models, self-purchasing medication was associated with an increased prevalence of gastric disease (adjusted OR = 1.75, 95% CI 1.46-2.09, p < 0.001), including Model 3 (adjusted OR = 1.75, 95% CI 1.46-2.09, p < 0.001). The model demonstrated moderate discriminatory ability in distinguishing individuals with and without gastric disease (AUC = 0.71). Stratified analyses revealed that the association between self-purchased medication use and gastric disease risk was consistent across covariates, with stronger effects observed in participants with CKD (adjusted OR = 1.89) and diabetes (OR = 1.82). CONCLUSIONS: This study found that self-purchasing medication was positively correlated with the risk of gastric disease in Chinese older adults (adjusted OR = 1.75), and the association was stronger among those with chronic kidney disease (adjusted OR = 1.89) or diabetes (OR = 1.82). This finding provides a reference for the risk stratification and prevention strategies of gastric disease.