Low Income Predicts Mortality Independently from the Presence of Type 2 Diabetes and Preexisting Coronary Artery Disease

A low socioeconomic status has been associated with increased mortality. Whether low income predicts mortality risk independently from the presence of type 2 diabetes (T2DM) and preexisting coronary artery disease (CAD) is not known and is addressed in the present study. We assessed the annual net income through a standardized questionnaire in a consecutive series of 438 patients referred to coronary angiography for the evaluation of established or suspected stable coronary artery disease (CAD). Prospectively, we recorded mortality over a mean follow-up period of 10.0±2.3 years. Annual net income was <€20.000 in 58.0%, €20.000-35.000 in 33.1% and >€35.000 in 8.9% of our patients. It was significantly lower in women (<€20.000 in 70.4%, €20.000-35.000 in 25.6%, >€35.000 in 4.0%) than in men (<€20.000 in 53.0%, €20.000-35.000 in 36.1%, >€35.000 in 10.9%; p<0.001) but did not differ significantly between patients with T2DM (n=116) and nondiabetic subjects (p=0.147) nor between patients with CAD (n=353) and those who did not have CAD at angiography (p=0.391). During follow-up, mortality significantly increased with decreasing income: it was 7.7%, 17.9%, and 25.6% in patients with net incomes of >€35.000, €20.000-35.000 and <€20.000, respectively; p=0.009). Annual net income significantly predicted the incidence of cardiovascular events both univariately (HR 0.59 [0.41-0.85]; p=0.004) and after adjustment for age, gender, smoking, LDL cholesterol, HDL cholesterol, hypertension, BMI, waist circumference, T2DM and angiographically determined baseline CAD (HR 0.61 [0.40-0.96]; p=0.033). We conclude that a low net income predicts cardiovascular event risk independently from the presence of T2DM and preexisting CAD.