Association of Income Level and Ischemic Heart Disease: Potential Role of Walkability

BACKGROUND

Association of Income Level and Ischemic Heart Disease: Potential Role of Walkability Association of ischemic heart disease (adjusted for traditional risk factors and socioeconomics variables) and income level (A), and walkability z-score (B), and association of walkability z-score and income level (C).

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. It is also uncertain whether walkability mediates this association.

OBJECTIVES

To investigate whether income is associated with IHD in a middle-income country 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 4 variables: street connectivity, residential density, commercial density, and mixed land use. IHD was defined by abnormal myocardial perfusion during a SPECT-MPI study. We used adjusted mixed effects models to evaluate the association between income level and IHD, and we performed a mediation analysis to measure the percentage of the income-IHD association mediated by walkability. We considered p values below 0.01 as statistically significant.

RESULTS

From 26,415 participants, those living in the lowest-income tertile census tract were more physically inactive (79.1% versus 75.8% versus 72.7%) when compared to higher-income tertile census tracts (p < 0.001). Income was associated with IHD (odds ratio: 0.91 [95% confidence interval: 0.87 to 0.96] for each 1,000.00 international dollars increase in income) for both men and women equally (p for interaction = 0.47). Census tracts with a 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 middle-income country irrespective of gender. Although walkability was associated with census tract income, it did not mediate the income-IHD association.

4223Income level and the prevalence of ischemic coronary heart disease in a low-mid-income country with high social inequalities. Influence of neighborhood walkability

Background

The greater burden of coronary heart disease (CHD) comes from low-middle income countries (LMIC). Socioeconomic status, environmental factors, poor access to healthcare, physical inactivity and excess consumption of carbohydrates, have explained part of this burden. However, the association between income level and CHD in LMIC with marked social inequalities is not fully understood, and whether there is influence of neighborhood walkability (walking-promoting potential of the residential built environment for daily activities) in this association requires further investigation.

Purpose

To investigate to what level income is associated with ischemic CHD in a LMIC with great social inequalities and to explore the potential role of neighborhood walkability in this association.

Methods

We evaluated patients referred for myocardial perfusion imaging with SPECT (SPECT-MPI) from February 2010 to August 2017 at a reference imaging center in our city, Brazil. Each patient was georeferenced and the exposure variable was the average income in Brazilian currency (Real) per month, from the patient's residential census block. Ischemic CHD was defined by an abnormal myocardial perfusion (summed stress score >3) during a SPECT-MPI study. Walkability was measured by a score combining street connectivity, residential density, commercial density and mixed land use. We used mixed effects models to evaluate the association between income level and ischemic CHD, adjusted for potential confounders, and performed a mediation analysis to measure the percentage of this association mediated by walkability.

Results

From 26,810 participants, those living in the lowest tertile income neighborhoods were younger (61±12 vs 63±13 vs 65±12 yrs old); with higher body mass index (28.4±5 vs 27.7±5 vs 27.4±4 kg/m2); more likely to be women (52 vs 49 vs 47%), current smokers (10 vs 9 vs 8%), sedentary (79 vs 76 vs 73%), having diabetes (27 vs 24 vs 23%), hypertension (65 vs 62 vs 60%) and with known CHD (21 vs 20 vs 19%) when compared to the second and the highest tertiles respectively, all with p<0.001. After adjusting for these potential confounders, income level was inversely associated with ischemic CAD (Figure). Neighborhoods with higher income levels were associated with better walkability scores (R = 0.34eta; p<0.001), but walkability did not mediate the association between income level and ischemic CHD (percent mediated = −0.3%).

Figure 1. Association of income and CHD

Conclusions

In this large registry from a LMIC population, living in a lower-income neighborhood was associated with higher prevalence of ischemic CHD. Even though neighborhood walkability was directly associated with neighborhood income, it did not explain the association between income level and ischemic CHD.