Background: Socioeconomic status has been linked to ischemic heart disease (IHD). High-income neighborhoods may expose individuals to a walking-promoting built environment for daily activities (walkability). Data from the association between income and IHD is lacking in middle-income countries (MIC). It is also uncertain whether walkability mediates this association.
Objectives: To investigate whether: income is associated with IHD in a MIC; and whether neighborhood walkability mediates the income-IHD association.
Methods: This cross-sectional study evaluated 44,589 patients referred for myocardial perfusion imaging (SPECT-MPI). Income and walkability were derived from participants’ residential census tract. Walkability quantitative score combined four variables: street connectivity, residential density, commercial density, and mixed land use. IHD was defined by an abnormal myocardial perfusion during a SPECT-MPI study. We used adjusted mixed effects models to evaluate the association between income level and IHD; and performed a mediation analysis to measure the percentage of the income-IHD association mediated by walkability.
Results: From 26,415 participants, those living in the lowest income tertile census tract were more physically inactive (79.1 vs 75.8 vs 72.7%) when compared to higher income census tracts (p<0.001). Income was associated with IHD (OR 0.90 [95%CI 0.87 – 0.94] for each US$ 1,000.00 increase in income). Census tracts with higher income were associated with better walkability (p <0.001), however, walkability did not mediate the income-IHD association (percent mediated = -0.3%).
Conclusions: Income was independently associated with higher prevalence of IHD in a MIC. Although walkability was associated with census tract income, it did not mediate the income-IHD association.