The lifetime cumulative risk of sudden cardiac death (SCD) is much higher in black patients than in whites, according to an analysis of the Atherosclerosis Risk in Communities (ARIC) Study published in Circulation Feb. 4.
The cohort study of 3,832 blacks and 11,237 whites in the ARIC database was designed to assess the risk of SCD between races in a large-scale, community-based setting, wrote first author Di Zhao, PhD, and colleagues at the John Hopkins University School of Medicine in Baltimore.
“Blacks have a higher incidence of out-of-hospital sudden cardiac arrest in comparison with whites, as evidenced in emergency medical service systems data in several U.S. cities,” the authors wrote. “In addition, in some but not all studies, survival from sudden cardiac arrest is worse in blacks in comparison with whites.”
Zhao et al. relied on self-reported race data from the ARIC study for their work, defining sudden cardiac death as “a sudden pulseless condition from a cardiac cause” in someone who was previously stable. All SCD cases were adjudicated by an expert committee, and the researchers considered demographic and socioeconomic information, cardiovascular risk factors, presence of coronary heart disease and electrocardiographic parameters as potential mediating factors between races.
Over 27 years of follow-up, the authors said 215 black patients and 332 white patients experienced SCD, making the lifetime cumulative incidence of SCD at age 85 years 9.6 percent for black men, 6.6 percent for black women, 6.5 percent for white men and 2.3 percent for white women. The sex-adjusted hazard ratio for SCD comparing blacks with whites was 2.12—a number that was still statistically significant after adjusting for other confounders.
Zhao and co-authors said that in mediation analysis, known risk factors explained 65.3 percent of the excess risk of SCD in blacks compared to whites. The single most important factor was income, explaining 50.5 percent of the difference, followed by education (19.1 percent), hypertension (22.1 percent) and diabetes (19.6 percent).
“The incidence of cardiac arrest was 30 percent to 80 percent higher in U.S. areas of lowest versus highest socioeconomic status,” the authors wrote. “The associations of income and education with SCD were similarly strong for blacks and whites, but blacks were four times more likely to be in the lowest income category. Income and education are upstream factors with wide implications on cardiovascular risk, including associations with multiple cardiovascular risk factors.”
Low income and education have also been linked to unhealthy behaviors, low disease awareness and limited access to care, they said, possibly contributing to poor SCD outcomes in those populations. Blacks also have a higher prevalence of mutations in the cardiac sodium channel variant SCN5A, which could mediate an increased risk of ventricular arrhythmias.
Zhao et al. said the increased risk associated with race in their study was more pronounced in women than in men, with CHD prevalence in blacks higher in women than in men. They said black women are a “particularly vulnerable” subgroup for SCD, and nonischemic heart disease like dilated cardiomyopathy and valvular heart disease might be a more common precursor of the condition in black women. But, they said, their analysis implies that intervention and control of known risk factors like hypertension should gradually reduce disparities between races and sexes.
“The high burden of SCD in the general population, particularly in blacks, requires better approaches to improve preventive measures,” the authors wrote. “Efforts to reduce the SCD risk in blacks should focus on improving cardiopulmonary resuscitation outreach, medical care engagement in response to cardiac arrest events and quality of treatment in medical institutions in predominantly black neighborhoods.”