Income, education, and the clustering of risk in cardiovascular disease in the US, 1999–2018: an observational study

Background: Health metrics in the United States (US) have lagged behind other high-income countries in recent decades, and show persistent gaps between socio-demographic groups. Top 20% income earners and college graduates have also increasingly diverged from the reminder of the population in various dimensions over the past few decades. This study described population patterns in cardiovascular diseases (CVD) by income and education over a twenty-year period. Methods: This analysis used nationally representative data from 10 cycles (1999-2018) of the National Health and Nutrition Examination Survey (NHANES). Participants were stratified by income and education into four groups: top 20% income earners, college graduates; top 20% income earners, non-college graduates; bottom 80% income earners, college graduates; and bottom 80% income earners, non-college graduates. For income, we created a binary variable (ratio > 5 cutoff) using NHANES income-to-poverty ratio variable to create a standardized measure of income. We calculated the age-standardized prevalence and odds ratios of four conditions: congestive heart failure (CHF), angina, heart attack, and stroke, for each income-education group. Findings: 49,704 participants reported data for both income and education. The age-standardized prevalence of CVD outcomes varied across the four groups. This was most significant when comparing the prevalence among the top 20% income, college graduate group to the bottom 80% income, non-college graduate group: CHF (0.5% vs. 3.0%), angina (1.4% vs. 2.8%), heart attack (1.7% vs. 3.9%), and stroke (1.1% vs. 3.4%). Compared to the top 20% income, college graduate group, the odds of all CVD conditions were significantly higher in the bottom 80% income groups (college graduates: odds ratios (ORs) 1.48-3.67; non-college graduates: ORs 2.36-6.52), as well as for CHF and heart attack in the top 20% income, non-college graduates (OR 3.11 [95% CI: 1.92, 5.06] and OR 1.92 [95% CI: 1.35, 2.73], respectively). Interpretation: Health gaps extend beyond extremes, with risk clustering favoring top 20% income earners with college degrees while most Americans are left behind. Future research should include longitudinal studies that focus on the mechanisms through which both income and education intersect to shape CVD outcomes in the US. Funding: The Rockefeller Foundation.