Impact of Individual Income Level on Late Mortality After Coronary Artery Bypass Grafting

Background: Coronary artery bypass grafting (CABG) is an important and viable option for patients with symptomatic or life-threatening ischemic heart disease. Few papers have explored whether socioeconomic status is a significantly important determinant in late outcomes of CABG, and individual-level socioeconomic data were particularly scarce. This study was conducted to explore the impact of individual income level on clinical outcomes after CABG. Methods: This nationwide longitudinal population-based study was conducted in South Korea using the National Health Insurance Service database. Overall, 29 810 adult patients who underwent first-time isolated CABG from 2005 to 2015 were included. The individual income level was stratified into 4 quartiles (Q1-Q4). The primary outcome was overall mortality. Results: After adjustment for preoperative comorbidities, no significant difference in the in-hospital mortality rate was observed between the lowest (income Q1 group) and highest (income Q4 group) quartiles. The risk of overall mortality increased significantly with a reduction in income level, and having an income in the lowest quartile was a significant predictor of worse late mortality compared with the highest quartile (hazard ratio, 1.23; 95% CI, 1.17-1.30). Moreover, the overall incidence of stroke and myocardial infarction was significantly higher in the income Q1 group than in the income Q4 group. The median follow-up duration was 7.0 years (interquartile range, 4.1-10.2 years). Conclusions: Patients with a lower individual income level had an increased risk of the poorer long-term outcomes after CABG compared with the highest individual income level quartile.