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Appreciating Cardiovascular Disease Risk in South Asians: The Time is Now

Disclosure: None
Pub Date: Thursday, May 24, 2018
Author: Nathan D. Wong, PhD, MPH, FAHA, FACC
Affiliation: Heart Disease Prevention Program, Division of Cardiology, University of California, Irvine

View the full Science News coverage for Atherosclerotic Cardiovascular Disease in South Asians in the United States: Epidemiology, Risk Factors, and Treatments

Citation

Volgman AS, Palaniappan LS, Aggarwal NT, Gupta M, Khandelwal A, Krishnan AV, Lichtman JH, Mehta LS, Patel HN, Shah KS, Shah SH, Watson KE; on behalf of the American Heart Association Council on Epidemiology and Prevention; Cardiovascular Disease in Women and Stroke and Special Populations Committee of the Council on Clinical Cardiology; Council on Cardiovascular and Stroke Nursing; Council on Quality of Care and Outcomes Research; and Stroke Council. Atherosclerotic cardiovascular disease in South Asians in the United States: epidemiology, risk factors, and treatments: a scientific statement from the American Heart Association [published online ahead of print May 24, 2018]. Circulation. DOI: 10.1161/CIR.0000000000000580.

Article Text

South Asians, deriving mainly from India, Pakistan, Bangladesh, Sri Lanka, and Nepal represent over 1.5 billion individuals, one-fifth of the world’s population1. Multiple waves of immigration of South Asians to North America, dating back to the late 18th century and continuing to the present day have brought the South Asian population to over 3.4 million in the United States as of the 2010 US Census, with approximately 80% being of Asian Indian origin. In recent decades, multiple reports have documented their increased atherosclerotic cardiovascular disease (ASCVD) risk; however this is not widely appreciated in the public and preventive strategies aimed to address their excess ASCVD risk remain inadequate among South Asians2.

In the AHA Scientific Statement on Atherosclerotic Cardiovascular Disease in South Asians in the United States published in this issue of Circulation, Volgman and colleagues explore the biologic and non-biologic mechanisms contributing to excess risk of ASCVD in South Asians as well as the current state of risk factor interventions used to reduce ASCVD risk2. They note that perhaps the most significant disparity compared to other ethnic groups is the excess prevalence of type 2 diabetes and impaired glucose tolerance. In fact, the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study has recently shown a prevalence of diabetes of 23%, nearly double that found in age and adiposity matched Chinese-Americas (13%) and four times that of non-Hispanic Whites (6%)3. The greater diabetic ASCVD risk in South Asians has been well-known for decades, and while 30 years ago an increase in mortality was seen among South Asians with type 2 diabetes in England and Wales, more recent data from the UK suggest this pattern may be reversing with lower mortality in those with type 2 diabetes of South Asian versus European descent, possibly because of better screening and treatment of risk factors, more second generation migrants, and early detection and treatment of diabetes4. It is not clear, however, whether this is the case among South Asians living in the United States.

Other major risk factor differences noted between South Asians and other ethnic groups in the US include specific dyslipidemias, namely elevated triglycerides and low HDL-C being more common in South Asians, and often secondary to diabetes and impaired fasting glucose, as well as elevated lipoprotein(a) levels which may further explain some of the excess ASCVD risk observed in South Asians. Moreover, they note the diets of South Asians are high in refined carbohydrates and saturated fat, and low in fruits and vegetables along with physical activity being lower when compared to other race/ethnic minorities. While these disparities in risk have been known for decades and the findings are not surprising, they underscore the need for greater educational efforts directed to healthcare providers to improve the identification of these problems in their South Asian patients, which may help to explain their excess ASCVD risk. What appears to be the case, however, is that these and other risk factor differences do not fully explain the excess cardiovascular risk present, and that there is a complex interplay between abdominal obesity and insulin resistance involving both genetic and environmental contributors that justifies South Asian ethnicity as an independent cardiovascular risk factor as has been previously proposed5.

A key first step in addressing the burden of ASCVD in South Asians is to increase their awareness of their cardiovascular risks and educate them about how to improve their risks through healthier lifestyles. The American Heart Association has championed the concept of cardiovascular health through educating the community about knowing their Life’s Simple 7™ –ideal levels of blood pressure, cholesterol, glucose / diabetes, weight/obesity, dietary, physical activity, and smoking status, and has promoted the use of My Life Check™ (opens in a new window)  as a useful tool for one to evaluate where one stands on each of these seven metrics, providing a summary “cardiovascular health score” and guidelines on what areas need improvement and how. Such a tool should be more widely promoted in the community at large, and modified (as well as other educational materials promoting heart health) for the cultural needs of South Asians. In addition, better use of global risk assessment tools by clinicians is crucial, such as the AHA/ACC risk calculator (although not yet validated in South Asians or other groups) or as Volgman and colleagues2 recommend, the QRISK2 calculator (opens in a new window) may be even more appropriate as it provides designation of South Asian ancestry. But while validated in South Asians, it is based exclusively on South Asians in the UK. Physicians caring for South Asians should not only be encouraged to use these tools to better inform clinical decision making but to promote the clinician-patient “risk discussion” about the best ways to reduce ASCVD risk through lifestyle as well as pharmacologic therapies. Moreover, given the greater subclinical disease observed in South Asians from several studies involving CT angiography, carotid intimal medial thickness / plaque, and coronary calcium, as well as inflammatory factors such as hs-C-reactive protein are elevated in South Asians, it may be reasonable to consider their assessment in further refining the treatment decision. The ACC/AHA risk assessment guidelines in fact recommends evaluation for premature family history of ASCVD (which should always be done as part of every patient risk evaluation), hs-C-reactive protein, coronary calcium, and ankle brachial index to further inform the treatment decision when uncertain based on global risk assessment alone6. As studies have shown South Asians to have similar7 or greater8 levels of coronary calcium relative to other ethnic groups and designation of coronary calcium by recent guidelines as perhaps the most useful of measures for risk stratification beyond global risk assessment6 suggests the potential usefulness of this tool for identifying early disease and for prompting earlier or more aggressive risk factor management in South Asians. The presence (or abnormalities in) of these factors can be an impetus for beginning or intensifying preventive treatments such as statins or antihypertensive medicines. On the other hand, given the increased baseline risk in this population, with up to 10% of ASCVD cases occurring below 45 years of age, some have called for consideration of prophylactic statin therapy for those above age 45 and lipid guidelines in India have gotten more strict at recommending statins at lower thresholds of risk in primary prevention9, 10. While generic statins are inexpensive in the United States, it is unlikely any national guideline in the near future will recommend their universal use as a prophylactic.

Besides the recommendation to calculate ASCVD risk, Volgman and colleagues2 also recommend using the International Diabetes Federation race-specific cutpoints for diagnosing abdominal obesity (as a component of the metabolic syndrome) specific to South Asians being >90 cm (35.4 inches) in men and >80 cm (31.5 inches) in women11. While waist circumference measures are seldom performed in the clinic, its value in identifying visceral adiposity and those likely to have other cardiometabolic risk factors cannot be understated, and these being significant issues in the South Asian population should hopefully motivate our healthcare providers to make waist circumference measurement a priority (over the less accurate body mass index frequently calculated from routine weight and height measurements) and groups such as the American Heart Association to advocate for it. Other recommendations note the need to increase educational efforts by targeting community gathering areas including temples and cultural and health fairs to improve awareness of CVD. The American Heart Association in general and their Community Impact Division (previously known as Multicultural Initiatives) programs can also further expand awareness through promoting Go Red for Women™ as well as My Life Check™ assessments and Target BP™ and Check Change Control Cholesterol™ programs to the South Asian community. Finally, at the individual doctor-patient level, the authors point out the need to demonstrate cultural competency in understanding the needs of South Asian patients and providing South Asian-specific recommendations on lifestyle and pharmacologic therapies2.

While the statement does provide a good review of lifestyle intervention trials done in South Asians and their findings, it was perhaps beyond the scope of this statement to provide specific guidance regarding South Asian-specific nutritional and physical activity modifications. This brings up the great opportunity for the American Heart Association to collaborate with groups with expertise in Asian Indian – specific nutritional needs, such as the Asian Indians in Nutrition and Dietetics group, as well as those with significant cardiovascular nutrition expertise, specifically the Sports Cardiovascular and Wellness Nutrition (SCAN) practice group, both groups within the Academy of Nutrition and Dietetics. These groups should work together to develop healthful approaches for modifying the South Asian diet (e.g., examples of food substitutions and menus that can be used), including culturally sensitive materials in nutrition and lifestyle management for the South Asian community. The predominance of obesity and diabetes as key factors explaining the cardiovascular risk in South Asians makes addressing their lifestyle determinants of particular priority.

The statement nicely describes some of the important findings from the MASALA prospective study of cardiovascular disease in South Asians living in the United States, probably the most relevant study we currently have to examine cardiometabolic risk and its consequences in an exclusively South Asian population. Continued follow-up of this cohort will yield valuable information about the value of traditional and newer risk factors as well as subclinical cardiovascular disease measures for the prediction of cardiovascular disease events. Because of comparable methodology it adopted based on the Multiethnic Study of Atherosclerosis, it has good validity to make comparisons to other major ethnic groups in the United States. Several needs for future research studies are also suggested, including better defining cutpoints for waist circumference and body mass index identifying increased risk in South Asians, determining optimal glucose cutpoints, improving and validating ASCVD risk calculators, and furthering research disaggregating Asian sub-populations to personalize recommendations2. As an example, only since 2011 has the US National Health and Nutrition Examination survey even separated out Asians and Pacific Islanders as an aggregate – further national surveys should consider further division by key major subpopulations, including East and South Asians, so that national statistics such as those reported out by American Heart Association’s Heart and Stroke Statistics12 can provide their data with this delineation, enabling us to identify where there may be treatment gaps in these populations (e.g., in hypertension or cholesterol control). Moreover, given the threshold for efficacy for certain therapies such as statins are often different in Asian populations, clinical trials should further examine whether different thresholds exist across different Asian subpopulations, such as comparing East and South Asians. Finally, with the problem of obesity and diabetes central to the increased cardiovascular disease risk in South Asians, it will be of great importance to examine in South Asians the efficacy of newer antidiabetic therapies shown to have cardiovascular benefits (e.g., SLGT-2 inhibitors and GLP-1 antagonists), as well as the role of emerging therapies aimed to target certain lipid disturbances common in South Asians, such as elevated lipoprotein(a).

The AHA Scientific Statement on Atherosclerotic Cardiovascular Disease in South Asians in the United States2 represents an important step in increasing awareness of the excess CVD risk in South Asians, the key risk factors that drive this risk, and provides specific recommendations for healthcare providers to better identify those at increased risk and on risk factor modifications needed to reduce the excess ASCVD burden in South Asians. The burden of ensuring its key messages are disseminated and implemented sufficiently to impact on ASCVD in our South Asian population falls on us as healthcare providers, scientists, and staff and volunteers of the American Heart Association, American College of Cardiology, American Society for Preventive Cardiology and other societies who care about this important and ever growing segment of the American population.

References

  1. Yusuf S, Joseph P. The epidemic of cardiovascular disease in South Asians: Time for action. Am Heart J. 2017; 185:150-153.
  2. Volgman AS, Palaniappan LS, Aggarwal NT, Gupta M, Khandelwal A, Krishnan AV, Lichtman JH, Mehta LS, Patel HN, Shah KS, Shah SH, Watson KE; on behalf of the American Heart Association Council on Epidemiology and Prevention; Cardiovascular Disease in Women and Stroke and Special Populations Committee of the Council on Clinical Cardiology; Council on Cardiovascular and Stroke Nursing; Council on Quality of Care and Outcomes Research; and Stroke Council. Atherosclerotic cardiovascular disease in South Asians in the United States: epidemiology, risk factors, and treatments: a scientific statement from the American Heart Association [published online ahead of print May 24, 2018]. Circulation. DOI: 10.1161/CIR.0000000000000580.
  3. Kanaya AM, Kandula N, Herrington D, et al. Mediators of Atherosclerosis in South Asians Living in America (MASALA) study: objectives, methods, and cohort description. Clin Cardiol. 2013; 36:713-720.
  4. Johns E, Sattar N. Cardiovascular and mortality risks in migrant South Asians with Type 2 Diabetes: Are We Winning the Battle?   Cur Diab Rep. 2017; 17:100
  5. Goff DC Jr, Lloyd-Jones DM, Bennett G, et al. American College of Cardiology/American Heart Association Task Force on Practice Guidelines. 2013 ACC/AHA guideline on the assessment of cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014; 63:2935-2959.
  6. Kanaya AM, Kandula NR, Ewing SK, et al. Comparing coronary artery calcium among US South Asians with four racial/ethnic groups: the MASALA and MESA studies. Atherosclerosis; 2014; 234:102-107.
  7. Hatwalkar A, Agrawal N, Reiss DS, Budoff MJ. Comparison of prevalence and severity of coronary calcium determined by electron beam tomography among various ethnic groups. Am J Cardiol; 2003; 91:1225-1227.
  8. Gupta M, Vrister S. Is South Asian ethnicity an independent cardiovascular risk factor?  Can J Cardiol. 2006; 22:193-197.
  9. Jain A, Puri R, Nair DR. South Asians: why are they at higher risk for cardiovascular disease?  Curr Opon Cardiol. 2017; 32:430-436.
  10. Iyengar SS, Puri R, Narasingan SN. Lipid Association of India Expert Consensus Statement on Management of Dyslipidemia in Indians 2016; Part 1 – executive summary. J Clin Prev Cardiol. 2016; 5:51-61.
  11. International Diabetes Federation. The IDF consensus worldwide definition of the metabolic syndrome. 2006; Available at: idf.org/webdata/docs/IDF_Meta_def_final.pdf
  12. Benjamin EJ, Virani SS, Callaway CW, et al. Heart Disease and Stroke Statistics-2018 Update: A Report from the American Heart Association. Circulation. 2018; Jan 31.

-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --