Racial Disparities in Patient Characteristics and Survival After AMI
To what degree do nonrace characteristics explain observed survival differences between white and black patients following acute myocardial infarction (AMI)?
The authors used a cohort study (TRIUMPH and PREMIER registries) with extensive socioeconomic and clinical characteristics from patients recovering from an AMI that were prospectively collected at 31 hospitals across the United States between 2003 and 2008. Survival was assessed using data from the National Death Index from December 2016 to July 2018. Patient characteristics were categorized into eight domains including age and sex, socioeconomic status, social support, lifestyle factors, medical history (major risk factors, prior MI, prior coronary revascularization, prior stroke or transient ischemic attack, chronic heart failure, left ventricular systolic function, chronic kidney disease, dialysis, chronic lung disease, and cancer), clinical presentation (ST-elevation MI, cardiac arrest, and initial hemoglobin), health status, and depressive symptoms. The degree to which each domain discriminated black from white patients was determined by calculating propensity scores associated with black race for each domain as well as cumulatively across all domains. The final propensity score was associated with 1- and 5-year mortality rates.
The study consisted of 6,402 patients with mean age 60  years; 2,127 [33.2%] female; and 1,648 [25.7%] black. The 5-year mortality rate following AMI was 28.9% (476 of 1,648) for black and 18.0% (856 of 4,754) for white patients (hazard ratio, 1.72; p < 0.001). Most categories of patient characteristics differed substantially between black and white patients. The cumulative propensity score discriminated race, with a C-statistic of 0.89, and the propensity scores were associated with 1- and 5-year mortality rates (hazard ratio for the 75th percentile of the propensity score vs. 25th percentile, 1.72; p < 0.001). Patients in the lowest propensity score quintile associated with being black had a 5-year mortality rate of 15.5%, while those in the highest quintile had a 5-year mortality rate of 31.0% (p < 0.001). After adjusting for the propensity associated with being black, there was no significant mortality rate difference by race (adjusted hazard ratio, 1.09; 95% confidence interval, 0.93-1.26; p = 0.37) and no statistical interaction between race and propensity score (p = 0.42).
Characteristics of white and black patients differed significantly at the time of admission for AMI. Those characteristics were associated with an approximate threefold difference in the 5-year mortality rate following AMI and mediated most of the observed mortality rate difference between the races.
While not conclusive, this important observational study with good geographic representation across the United States questions the long-held concern that treatment differences and quality of care are responsible for difference between races in outcomes following AMI. Socioeconomic and social factors that are seldom incorporated into risk models were two of the most important factors differentiating white and black patients.
Keywords: Acute Coronary Syndrome, African Americans, Depression, European Continental Ancestry Group, Heart Arrest, Heart Failure, Hemoglobins, Ischemic Attack, Transient, Life Style, Lung Diseases, Myocardial Infarction, Neoplasms, Primary Prevention, Renal Insufficiency, Chronic, Risk Factors, Social Class, Social Support, Socioeconomic Factors, Stroke
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