Abstract
BACKGROUND: Angina, a major manifestation of ischaemic heart disease, affects 3-7% of adults and is a leading cause of cardiovascular morbidity. As an ambulatory care-sensitive condition, its outcomes can be improved through proactive outpatient management. However, the real-world impact of continuity of care (COC) and medication adherence, measured by the medication possession ratio (MPR)-on angina complications in South Korea remains poorly understood. OBJECTIVE: This study evaluated the effectiveness of COC and MPR in patients with angina using comprehensive national data and examined the outcomes at the hospital level. METHODS: This retrospective cohort study used data from the National Health Insurance Service of Korea between 2002 and 2019. We identified 11 127 patients aged >30 years newly diagnosed with angina, applying strict exclusion criteria to ensure cohort validity. COC was categorised as high (COC index=1.0) or low (<1.0), and MPR was classified as excellent (≥80%), good (60%-79%) or poor (<60%). Complications, defined as the onset of coronary artery disease (International Classification of Diseases, 10th Revision: I20-I25), were analysed using Kaplan-Meier survival curves and Cox proportional hazards models, adjusting for key sociodemographic and clinical covariates. RESULTS: Among the study cohort (mean age 63.4 years; 54.3% female), 64.2% had low COC. While patients with low COC had a 20% higher risk of complications compared with those with high COC (HR: 1.20; 95% CI: 0.87 to 1.65; p=0.266), this was not statistically significant. Similarly, patients with poor MPR had a modestly elevated but non-significant risk (HR: 0.96; 95% CI: 0.67 to 1.36). Subgroup analysis revealed significantly elevated complication risk in patients ≥80 years with low COC (HR: 2.00; 95% CI: 1.67 to 2.32; p=0.04). The lowest complication rates were observed in patients receiving care from clinics with high COC and excellent MPR. CONCLUSIONS: Higher levels of COC and MPR were associated with reduced angina-related complications, underscoring their importance in chronic disease management. However, the inconsistent statistical significance suggests disease-specific strategies may be needed to optimise continuity and adherence interventions. These findings have implications for refining ambulatory care models and enhancing chronic disease policies within Korea's single-payer system.