Risk for ASCVD among South Asians may be underestimated by current risk calculators
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Atherosclerotic CVD was more prevalent among individuals of South Asian ancestry compared with those of European ancestry, a finding not explained by the addition of various risk factors to the Pooled Cohort Equations, researchers reported.
According to data published in Circulation, elevated risk for ASCVD events among individuals of South Asian ancestry may be associated with social determinants of health, other unmeasured risk factors and genetics.
“We need to dig deeper to better understand why South Asians are having heart attacks and strokes at higher rates even after accounting for these risk factors,” Aniruddh P. Patel, MD, cardiology fellow at Massachusetts General Hospital, said in a press release. “Our ability to study South Asian and other populations in general in the United States using public databases has been limited because individuals are grouped together by race rather than ancestry. This makes recognizing and addressing these disparities among a fast-growing South Asian population in the U.S. more difficult. In addition to recruiting more South Asians in clinical trials and cohort studies, better reporting of ancestry in addition to race in hospital data systems and electronic medical records would help us better understand and target these disparities.”
According to the study, individuals of South Asian ancestry represent 1.8 billion people, or approximately 23% of the global population.
For this prospective analysis of data from the UK Biobank that included 8,124 participants of South Asian ancestry (mean age, 54 years; 52% men) and 449,349 participants of European ancestry (mean age, 57 years; 44% men) with no ASCVD at baseline, researchers assessed the relationship between ancestry and risk for an ASCVD event (MI, coronary revascularization or ischemic stroke).
ASCVD risk among South Asian vs. European individuals
Compared with individuals of European ancestry, those of South Asian ancestry more often reported a history of diabetes (19.5% vs. 5.3%), income less than 18,000 British pounds (31.4% vs. 21.4%), central adiposity (waist-hip ratio, 0.9 vs. 0.87) and prescription of BP medications (24% vs. 19.4%).
Researchers reported that during a median follow-up of 11 years, 6.8% of the South Asian cohort experienced an ASCVD event compared with 4.4% of the European cohort. This finding represented a more than twofold greater risk among individuals of South Asian vs. European ancestry that remained consistent across age, sex and clinical subgroups (HR = 2.03; 95% CI, 1.86-2.22; P <.001).
Despite the greater observed risk, the 10-year risk for ASCVD among individuals of South Asian ancestry, as predicted by the American Heart Association/American College of Cardiology Pooled Cohort Equations (4.8% vs. 6%) and QRISK3 (9.7% vs. 8.3%), was similar to the predicted risk among those of European ancestry.
“The higher ASCVD risk for South Asian individuals was not predicted by the American College of Cardiology/American Heart Association Pooled Cohort Equations, likely because the populations used to derive these models lacked individuals of South Asian ancestry,” the researchers wrote. “The current QRISK3 calculator accounts for South Asian subgroup ancestry using a multiplicative factor variable ranging from approximately 1.3 to 1.7 according to country of origin. The findings of residual risk in this study after accounting for the list of risk factors lend further credence to such an approach but suggest that even these correction factors may not be adequate to fully capture the higher risk.”
According to the study, the heightened risk for ASCVD events among those of South Asian ancestry was not captured by either of the risk calculators and was only modestly attenuated by the addition of traditional and emerging risk factors (HR = 1.45; 95% CI, 1.28-1.65; P < .001).
“Despite accounting for these imbalances in prevalence and influence of traditional and emerging risk factors between individuals of South Asian and European ancestry, a residual unexplained risk remains, raising the possibility of genetic causes,” the researchers wrote. “We and others have recently started to assess the relationship of a polygenic predictor of ASCVD in South Asian individuals and to establish larger reference populations that may identify common or rare genetic factors distinct to South Asian individuals.”
‘A unified, global effort’
In a related editorial, Namratha R. Kandula, MD, MPH, co-director of the Institute for Public Health and Medicine at Northwestern University, and Alka M. Kanaya, MD, professor of medicine at University of California, San Francisco, discussed the elevated ASCVD risk among individuals of South Asian ancestry overlooked by current predictive models and the need to invigorate efforts in reducing CV disparities within this large population.
“We now have several prospective cohort studies showing that cardiovascular health disadvantages of South Asians in Europe and North America cannot be explained by traditional risk factors, and that there are important differences by country of origin,” Kandula and Kanaya wrote. “There is now the need to advance a unified, global effort to fully understand and address ASCVD disparities in South Asians. Studying the health of South Asian immigrants provides a key opportunity to understand how heterogeneity in sociocultural, environmental, interpersonal and individual factors underlie ASCVD disparities by country of origin, but very few studies have examined these relationships in large samples and with more detailed socioecological measures.
“The reasons underlying the increased risk of cardiovascular and metabolic disease are still not known, and solving this puzzle is of tremendous global importance,” Kandula and Kanaya wrote. “Future studies should enroll adequate samples to disaggregate South Asian subgroups and utilize a conceptual framework-driven approach to articulate and understand mechanisms that link drivers of cardiovascular health at the contextual, interpersonal and individual level.”
Reference:
Kandula NR, et al. Circulation. 2021;doi:10.1161/CIRCULATIONAHA.121.055159.
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