Racial differences in prevalence and impact of electrocardiographic subclinical myocardial injury risk factors

Background: We explored whether the reported racial differences in subclinical myocardial injury (SCMI) are due to variations in the prevalence or differential impact of the SCMI risk factors. Methods: This analysis included 3074 Whites, 1337 Blacks, and 1441 Mexican Americans from the Third National Health and Nutrition Examination Survey who were free of cardiovascular disease. SCMI was defined from standard electrocardiograms as a cardiac infarction/injury score >= 10 points. Multivariable logistic regression analysis was used to assess the association of SCMI with its risk factors stratified by race. Multiplicative interaction between each risk factor and race was also examined. Results: Overall prevalence of SCMI was 20.3%, with Mexican Americans exhibiting a lower prevalence than Whites and Blacks (16.5%, 20.4%, and 20.7%, respectively). Whites had more prevalence of dyslipidemia and smoking. Mexican Americans had more diabetes, while Blacks had more hypertension, obesity, and left ventricular hypertrophy. Significant risk factors for SCMI were older age, lower income (<20 K), smoking, diabetes, and no regular exercise. The association of SCMI with age was more pronounced in Mexican Americans (p-value for interaction 0.03), whereas the associations of SCMI with smoking, no-regular exercise, and diabetes were stronger in Whites (p-value for interaction 0.04, 0.001, 0.007, respectively). Conclusions: Heterogeneity in the racial differences in the prevalence of SCMI risk factors exists, but they do not explain racial differences in SCMI. The stronger associations of smoking, diabetes, and no regular exercise with SCMI partially explain the higher prevalence of SCMI in Whites.