Socioeconomic Factors, Secondary Prevention Medication, and Long-Term Survival After Coronary Artery Bypass Grafting: A Population-Based Cohort Study From the SWEDEHEART Registry

Abstract

Background Low income and short education have been found to be independently associated with inferior survival after coronary artery bypass grafting (CABG), whereas the use of secondary prevention medications is associated with improved survival. We investigated whether underusage of secondary prevention medications contributes to the inferior long-term survival in CABG patients with a low income and short education. Methods and Results Patients who underwent CABG in Sweden between 2006 to 2015 and survived at least 6 months after discharge (n=28 448) were included in a population-based cohort study. Individual patient data from 5 national registries, including the SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry, covering dispensing of secondary prevention medications (statins, platelet inhibitors, β-blockers, and RAAS inhibitors), socioeconomic factors, patient characteristics, comorbidity, and long-term mortaity were merged. All-cause mortality risk was estimated using multivariable Cox regression models adjusted for patient characteristics, baseline comorbidities, time-updated secondary prevention medications, and socioeconomic status. Long-term mortality was higher in patients with a low income and short education. Statins and platelet inhibitors were dispensed less often to patients with a low income, both at baseline and after 8 years. The decline in dispensing over time was steeper for low-income patients. Short education was not associated with reduced dispensing of any secondary prevention medication. Use of statins (adjusted hazard ratio=0.57 [95% CI, 0.53-0.61]), RAAS inhibitors (adjusted hazard ratio=0.78 [0.73-0.84]), and platelet inhibitors (adjusted hazard ratio=0.74 [0.68-0.80]) were associated with reduced long-term mortality irrespective of socioeconomic status. Conclusions Secondary prevention medications are dispensed less often after CABG to patients with low income. Underusage of secondary prevention medications after CABG is associated with increased mortality risk independently of income and extent of education.

Keywords: coronary artery bypass grafting; medication; mortality; secondary prevention; socioeconomic status.

Figure 1

Flowchart describing included and excluded patients. CABG indicates coronary artery bypass grafting.

Figure 2

Use of medication over time by income level in coronary artery bypass grafting patients, at baseline, after 4 years and after 8 years. Shaded area represents 95% CIs based on binomial distribution. CABG indicates coronary artery bypass grafting; Q1 to Q5 income quintile (Q1=lowest level); RAAS, renin‐angiotensin‐aldosterone system.

Figure 3

Use of medication over time by education level in coronary artery bypass grafting patients at baseline, after 4 years and after 8 years. Shaded area represents 95% CIs based on binomial distribution. RAAS indicates renin‐angiotensin‐aldosterone system.

Figure 4

Multi‐adjusted effects of time‐updated secondary prevention medications on all‐cause mortality among coronary artery bypass grafting patients. Hazard ratios for use of time‐updated use of medication vs no use of medication (reference) are presented for each socioeconomic status category. HR indicates hazard ratio; Q1 to Q5, income quintiles (Q1=lowest level); RAAS, renin‐angiotensin‐aldosterone system.