Stigma moderates the relationship between health literacy and medication adherence among rural elderly pulmonary tuberculosis patients: a cross-sectional study

Background Rural elderly individuals are a high-risk population for pulmonary tuberculosis (PTB). Medication adherence is critical for treatment success but is often compromised by low health literacy and high stigma. This study aimed to investigate whether stigma moderates the relationship between health literacy and medication adherence. Methods In December 2024, a consecutive sampling method was used to recruit 283 rural elderly PTB patients who had completed four months of anti-tuberculosis treatment from 18 tuberculosis prevention and control institutions in Henan Province. Sociodemographic and clinical data were collected, and validated Chinese scales for health literacy, stigma, and medication adherence were used. Spearman correlation, simple linear regression, and hierarchical regression (controlling for 9 covariates) were performed to analyze main effects and moderating effects, followed by Johnson‑Neyman analysis and sensitivity analysis. Results Health literacy was positively correlated with medication adherence (ρ = 0.227, P < 0.001), and stigma was negatively correlated with medication adherence (ρ = -0.210, P < 0.001). Hierarchical regression showed that the health literacy×stigma interaction term was significant (b = 0.005, 95% CI 0.001–0.008, P = 0.010), whereas ordinal logistic regression yielded only marginal significance (OR = 1.004, P = 0.061). Simple slope analysis indicated that the effect of health literacy was not significant at low stigma (b = 0.017, P = 0.303) but was significant and stronger at high stigma (b = 0.076, P < 0.001). The Johnson‑Neyman threshold was a raw stigma score > 2.72, exceeding which 63.25% of patients fell. Sensitivity analyses showed generally consistent patterns, although the ordinal logistic regression yielded only marginal significance, the moderation finding should therefore be considered exploratory. Conclusions The present study offers exploratory evidence suggesting that stigma may play a moderating role in the relationship between health literacy and medication adherence. This moderating pattern suggests that the association between health literacy and adherence may be more pronounced among rural elderly PTB patients with high stigma. Routine assessment of stigma and targeted health education for those with high stigma could be considered, although the efficacy of such stratified strategies remains to be validated by future interventional research. Trial registration Not applicable.