Association of median household income with burden of coronary artery disease among individuals with diabetes.

BACKGROUND

Low income is associated with adverse cardiovascular outcomes. Diabetes is more prevalent among low income groups, and low income patients with diabetes have been shown to have a greater burden of cardiovascular risk factors and worse cardiovascular outcomes. The objective of this study was to determine whether income status was associated with burden of coronary atherosclerosis in patients with diabetes.

METHODS AND RESULTS

All patients with diabetes presenting for cardiac catheterization between January 1, 2000, and December 31, 2002, in Calgary, Canada, were identified through the use of the Alberta Provincial Project for Assessing Outcomes in Coronary Heart Disease (APPROACH) database. This clinical database was merged with Canadian 2001 Census data on median household income per dissemination area using patient postal code data, and income quintiles were derived. Clinical profiles, severity of coronary atherosclerosis, and myocardial jeopardy were compared across income quintiles. Mean scores for severity and jeopardy were compared across income quintiles using analysis of variance. Multivariate linear regression was used to control for baseline differences across income groups. A total of 4596 patients were eligible for inclusion in this study. Clinical profiles differed significantly across income quintiles, with the highest income quintile being younger (P<0.0005), more likely to be male (P=0.029), and having a lower prevalence of smoking (P=0. 039). Low income groups were more likely to report a history of myocardial infarction (P<0.0005) or congestive heart failure (P<0.0005). The highest income groups has significantly less coronary atherosclerosis as measured by the weighted Duke index (6.67 versus 7.38, P<0.002), but there were no differences in lesion severity as measured by the Duke severity scale (2.31 versus 2.41, P=0.334). High income patients has significantly less myocardial jeopardy compared with the lowest income group as measured by the Duke and APPROACH scores (36.44 versus 46.23, P=0.0187, and 39.96 versus 45.36, P=0.0182, respectively). These differences remained significant even after controlling for baseline clinical differences in cardiovascular risk factor burden.

CONCLUSIONS

Low income is associated with a greater degree of atherosclerosis and greater myocardial jeopardy in patients with diabetes. More needs to be done to reduce cardiovascular risk factor burden in this vulnerable population.