Addressing disparities in ASCVD within the US South Asian population

The South Asian population in the U.S. is one of the fastest-growing minority ethnic groups, and these individuals are a particularly higher-risk population.

The U.S. South Asian population has rates of atherosclerotic CVD approximately 2.5 times greater than other racial and ethnic groups, particularly when compared with non-Hispanic white individuals. In addition to an increased prevalence of ASCVD, the development of atherosclerosis and subsequent clinical consequences (specifically, MI) often occurs approximately 5 years earlier in South Asian patients compared with their non-Hispanic white counterparts (Figure 1).

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These disparities persist even after controlling for the overall presence of established ASCVD risk factors. Traditional risk factors used for risk assessment of ASCVD such as type 2 diabetes/glucose intolerance, overweight/obesity status and dyslipidemia are found with a higher prevalence in South Asian individuals compared with non-Hispanic white and European individuals (Table).

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A closer look at diabetes

South Asian adults in the U.S. have a higher rate of prediabetes, type 2 diabetes and transitioning to type 2 diabetes compared with non-Hispanic white, Black, Hispanic and Chinese adults. Further differences are observed when analyzing South Asian subpopulations (Figure 2). Additionally, Asian Indian adults are diagnosed with type 2 diabetes approximately 5 to 10 years younger compared with non-Hispanic white adults.

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The etiology of type 2 diabetes is multifactorial and attributed to a combination of factors, but South Asian individuals are at higher risk for developing type 2 diabetes at lower BMI values (even when accounting for other traditional risk factors). These findings have informed recommendations by the American Diabetes Association and WHO that suggest screening for type 2 diabetes at a lower cutoff of a BMI of at least 23 kg/m², a waist circumference of at least 90 cm or a waist-to-height ratio of at least 0.39.

Dyslipidemia

South Asian adults generally have lower/similar levels of LDL and lower levels of HDL compared with non-Hispanic white adults. The protective nature of HDL may be blunted in South Asian individuals. Furthermore, South Asian individuals had a lower mean LDL compared with all other Southeast Asian subgroups (mean LDL, 125 mg/dL vs. 150 mg/dL) during their hospitalization for MI, suggesting that South Asian individuals may be at an elevated ASCVD risk even at lower LDL concentrations. This may be partially explained by South Asian adults having smaller and less dense LDL particles; therefore, they may carry a higher atherogenic particle load.

Understanding the sociocultural context of health

Recognizing sociocultural factors that impact health behaviors is essential for clinicians caring for South Asian patients. For example, concerns for cultural modesty, gender norms and communication gaps with the health care system may contribute to lower physical activity rates among certain South Asian adults. This also appears to differ by generation (ie, first- vs. second-generation South Asian individuals).

Tobacco use is also largely underestimated in the South Asian population, as many standard tobacco questionnaires do not appropriately capture cultural forms of smoked and smokeless tobacco such as hookah, chilam, gutkha and naswar.

Socioeconomic variability within South Asian subgroups can also contribute to large differences in health-seeking behavior. Differing views on alternative medicine, fears of drug toxicity and the stigma toward “Western medicine” play an important role in how South Asian individuals make decisions about their health care. Understanding these factors will allow clinicians to provide culturally sensitive advice around exercise, tobacco cessation and nutrition.

Accuracy of ASCVD risk calculators

While adjusting cutoffs and adapting estimation calculators may be prudent (ie, screening South Asian patients with BMI 23 kg/m² to screen for type 2 diabetes or considering testing for lipoprotein(a) among those with a family history of ASCVD), other differences found in the prevalence of obesity, nutrition, physical activity level and tobacco use may require a more nuanced and personalized evaluation of cultural practices, family history, length of stay in the U.S. and health care literacy.

The heterogeneous nature of the South Asian population impacts our ability to assess and manage ASCVD risk in this group. Commonly used risk assessment models have clear limitations and shortcomings that often lead to an underestimation of risk. The American College of Cardiology/American Heart Association Pooled Cohort Equation did not include South Asian individuals as a cohort in the development of their models but did classify South Asian ethnicity as a risk enhancer. Recent investigations suggest that both the Pooled Cohort Equation and Framingham Risk Score underestimate ASCVD risk even when applying crude adjustment values that some guidelines recommend. Other guidelines suggest no changes to risk calculation but rather encourage assessment for South Asian patients at younger years compared with their other ethnic counterparts.

Improving our ability to estimate risk can be difficult. Cultural and lifestyle differences within the various South Asian subgroups make it difficult to make generalized disaggregated adjustments to existing models. Additionally, without sorting through the differences between native and migrant populations, meaningful CVD risk factor discrepancies are often masked. Because of our inadequate ability to accurately assess risk and the overall heterogeneity of risk factor prevalence, culture and health-seeking behavior, there exists a need for more personalized and accurate ASCVD risk assessment.

Potential role of CAC scoring

Coronary artery calcium scoring provides a cost-effective, objective and reproducible marker to assess personalized atherosclerosis burden. When assessing measures of CAC among South Asian adults in correlation with the Pooled Cohort Equation, South Asian patients have often been found to have increased CAC burden within a higher number of vessels compared with patients from other ancestries that were in similar risk groups.

CAC scoring improves risk assessment to guide the intensity of preventive lifestyle and pharmacotherapy. It can be beneficial when informing clinicians and patients about the need for intensification of BP therapy and statin initiation within low- and intermediate-risk patients by the Pooled Cohort Equation. Considering diabetes and dyslipidemia are shown to be disproportionally prevalent in the South Asian population, traditional risk assessment in conjunction with selective use of CAC scoring may be of clinical importance.

Improving risk factor management

There exist gaps in the current literature that thoroughly investigate the etiology of increased ASCVD risk among South Asian adults, but improvements are expected with maturation of the MASALA, MASALA 2G, Our Health and other prospective studies. A recent manuscript from Anandita Agarwala, MD, a preventive cardiologist and women’s heart specialist at The Heart Hospital Baylor Plano, Baylor Scott & White Health and clinical assistant professor at Texas A&M University College of Medicine, and colleagues provides high-quality evidence-based recommendations to help guide ASCVD risk identification and management in South Asian adults. As further efforts to improve risk estimation in this population are needed, incorporation of personalized risk stratification with the selective use of CAC scoring may better inform clinicians when pursuing intensification of therapies for risk factor management.

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For more information:

Christopher Chew, MD, is an internal medicine resident at Johns Hopkins Medicine.

Priyanka Satish, MD, is a cardiology fellow at Houston Methodist DeBakey Heart and Vascular Center. Twitter: @psatishmd.

Roger S. Blumenthal, MD, is director of the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease and professor of medicine at Johns Hopkins University School of Medicine. He is also the editor of the Prevention section of the Cardiology Today Editorial Board. Twitter: @rblument1.

Jaideep Patel, MD, is a cardiologist at Johns Hopkins Heart and Vascular Institute and director of preventive cardiology at GBMC Health Care. Twitter: @jaideeppatelmd.

The authors can be reached at Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, Division of Cardiology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Halsted 560, Baltimore, MD 21827.