Social Factors Contribute to Race Differences in Premature CVD: CARDIA

The significantly higher risk of premature cardiovascular disease seen among Black participants in the CARDIA study compared to their white counterparts can be explained primarily by clinical factors, but neighborhood, socioeconomic, and lifestyle factors also come into play, researchers report.

It is well known that a variety of interrelated psychosocial factors affect cardiovascular outcomes—and that there are major race- and sex-based differences—but the study, published online last week in Circulation, was designed to take a deeper look.

“This approach that we took, it wasn't just about identifying which factors explain the differences between Black adults and their white adult counterparts, but also what was the relative contribution,” lead author Nilay Shah, MD (Northwestern University Feinberg School of Medicine, Chicago, IL), told TCTMD. “Because the idea was that if we could learn what some of the largest contributors to these differences were, it will start to provide a groundwork for what are likely to be some of the more-effective interventions to narrow the disparities that are prevalent in cardiovascular disease in the US.”

Looking at the web of risk factors that affect CVD, Harriette Van Spall, MD, MPH (McMaster University, Hamilton, Canada), who was not involved in the study, told TCTMD “it's a complex issue because those clinical factors in themselves are known to be related to socioeconomic factors, and in particular, to structural racism. So, it's hard to uncouple those factors because we know that even the clinical factors themselves are more common in patients who are Black, who are historically marginalized, who are subjected to systemic racism, and these socioeconomic drivers also give rise to some of the lifestyle factors that are being analyzed, such as smoking.”

What Affects Race-Based Differences?

For the study, Shah and colleagues looked at data on 2,785 Black and 2,327 white participants of the CARDIA study who were followed for a median 33.9 years.

After adjustment for age and hospital, Black women (HR 2.44; 95% CI 1.71-3.49) and Black men (HR 1.59; 95% CI 1.20-2.10) were at significantly higher risk for premature CVD than their white counterparts. However, these differences were ameliorated after full adjustment for clinical, lifestyle, psychosocial, socioeconomic, and neighborhood factors.

For women, race-based differences were explained mostly by clinical factors (87% reduction in the β estimate after adjustment), followed by neighborhood (32%) and socioeconomic (23%) factors. For men, clinical factors also contributed most strongly (64%), but socioeconomic (50%) and lifestyle (34%) factors also contributed.

Shah explained that while the factors affecting race-based differences did change over time, this was accounted for in their analysis. “The CARDIA study followed participants for over 30 years, but in those 30 years, the participants had somewhere on the order of 10 follow-up exams in the interim,” he said. “The way we designed our analysis is that every time a participant had an updated value for one of these factors, we accounted for the change in those factors. So when we were looking at the contribution of these factors to racial differences in premature cardiovascular disease, it wasn't just the factor at one level, but it was the factor and how it changed over the course of the 30 years.”

Vast Implications

This is powerful data not only for clinicians, but especially for policy makers. “With the growing recognition that these differences in heart disease between racial groups are not because of biological differences, the emphasis at multiple levels is to really understand and address the factors that we identified as contributing to the differences,” Shah continued. For one, he said, clinicians should be inquiring about the social determinants that may affect the health of their patients and how those factors—things like obesity and hypertension—can contribute to race-based disparities.

“At the policy level, when we think about the contribution of things like neighborhood-level environments and lifestyle factors—which account for factors like neighborhood-level poverty and the ability to participate in physical activity in built environments and the quality of diets that individuals are consuming—there are policy interventions that may target these factors that play the largest role in explaining these differences to actually be most effective at reducing disparity,” he added.

Van Spall agreed. “We really need to do a better job at the public health level and the population level in our policy—not just health policy, but social justice, education, and urban design—in order to really tackle the problem of cardiovascular disease and race-based differences in outcomes,” she said.

For physicians, it might be easier prescribe a therapy for hypertension, say, than to address challenging socioeconomic factors that patients live with, but “we see some of those factors manifest themselves in our patients' ability to make it to their appointments, to fill their prescriptions, and engage in self-care activity,” she said. “We need to account for these with compassion.”

Moreover, many of these patient groups have long been “marginalized in our healthcare system such that they don't receive the care for those risk factors,” Van Spall continued. “It's different in a registry when patients are routinely being contacted to see how they're doing to measure those risk factors for the incidence of cardiovascular disease, [but] in reality those patients receive less care in real-world situations, so we need to be mindful of that.”

As for next steps, Shah said he would like to better “understand the contribution of social determinants not to cardiovascular disease events, but actually to cardiovascular health and cardiovascular risk factors, because we suspect that a big component of the differences in cardiovascular risk factors or these clinical factors that we identified is actually also due to social determinants.”

Also, he said, clinical assessment of patients can improve by better incorporating consideration of social determinants of health.

Van Spall said “it would be interesting to measure in a robust manner how health policy changes impact population-level risk factors and outcomes. Higher-level interventions are harder to test robustly in clinical trials, and those types of studies need to get done because policy needs to be informed on evidence and it often isn't. . . . There are different ways to assess relative contributions and each really gives you a different set of results. There's no doubt that clinical risk factors drive cardiovascular disease, but the clinical risk factors are driven by other factors that we must recognize.”