American Heart Journal
Volume 159, Issue 1 , Pages 1-14, January 2010

Race, ethnicity, and heart disease: A challenge for cardiology for the 21st century

  • Vivian S. Rambihar, MD, FACC

      Affiliations

    • Department of Medicine, University of Toronto and The Scarborough Hospital, Toronto, Ontario, Canada
    • ,
  • Sherryn P. Rambihar, MD, FRCPC

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario, Canada
    • ,
  • Vanessa S. Rambihar, BHSc

      Affiliations

    • University of Toronto, Toronto, Ontario, Canada

Received 21 October 2009; accepted 21 October 2009.

Article Outline

 

Of all the forms of inequality, injustice in health care is the most shocking and inhumane.

Martin Luther King, Jr, 1966.

Fifty years ago, Danaraj et al1 (Figure 1) reported excess early myocardial infarction, mortality, and severe coronary heart disease in young Indians in Singapore, published in this Journal and reprinted in this issue. Fifty years later, this continues unchanged among the 25 million people of Indian origin worldwide and >1 billion in South Asia.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 Twenty-five years ago, this Journal also reported unexplained racial variation in coronary artery bypass graft use from one institution in the United States, with continuing reports of health disparities for blacks, Hispanics, and Native Indians in the United States reported in 2009.15, 16 Evidence of similar disparities in many countries has made the elimination of racial, ethnic, and other disparities in health, national priorities, and a health care equity and quality issue.9, 15, 16, 17 Globalization, increasingly multiethnic communities, and predicted worsening of disparities from obesity and global crises make this a continuing challenge for cardiology.6, 9, 17

Race, ethnicity, and health research is contentious, complex, and changing, becoming one of many ways of addressing health disparities.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 What started as epidemiology to understand and explain differences, is now used to create change and improve outcomes. The terms race and ethnicity are often used together or interchangeably, their complex meanings merging. Race is a social construct of shared external characteristics and social history, with limited biologic validity.9 Ethnicity includes overlapping social and cultural features such as ancestry, culture, customs, food, and language, as an evolving and complex variable that impacts health.6, 9, 17 Health is a dynamic process influenced by complex and dynamic interactions of biology, behavior, and environment, with diet and lifestyle modifying genetic or biologic predisposition.18

Race and ethnicity affect health through complex and dynamic interactions of associated factors. Social, political, and economic factors such as income, deprivation, access, education, barriers, language differences, racism, different health systems, and others interact with biologic factors and through social networks, demonstrated for smoking and obesity, to increase risk factors for disease.6, 9, 16, 17 There are no genes for racial or ethnic groups, with more diversity within than between them, although genetic studies can track geographic origins, population movements, and disease associations. Genetic factors with different prevalence in racial and ethnic groups, contribute to differences in gene expression and disease, whereas epigenetics allow transmission beyond genes. Multiple genes and gene-products for cardiovascular disease (CVD) interact with each other and the environment to increase CVD.

The publication by Danaraj1 in 1959 was the first to identify excess and premature CVD in Indian migrant men, reported since for South Asian men and women globally.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 In this necropsy study from 1950 to 1954 in Singapore, coronary heart disease (CHD) was 50% of all heart disease causes in Indian men but 20% in Chinese (with coronary disease 28.3% vs 4.5%) and complicated CHD (27% vs 3.4%), with small numbers for Europeans and Malays.1 The age-specific CHD mortality was much higher in Indians, especially between 40 and 49 years, 120/100,000 per year versus 17.1, despite similar age-specific death rates.1 Muir2 reported similar findings in 1960, with Wattley and Shaper mentioning similar ethnic differences in 1959.3, 4 South Asian refers to people with ancestry from India, Pakistan, Bangladesh, Sri Lanka, Nepal, and Bhutan, called Indian, Asian, or Asian Indian in different countries, with a similar pattern of excess risk reported.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 The reported high risk for the 3 million US South Asians is hidden in the diverse Asian or Asian and Pacific Islander group, with average lower risk.

Widespread South Asian migration led to recognition of similar excess risk reported from Uganda, Guyana, Mauritius, South Africa, Fiji, Trinidad, and United Kingdom from 1950s to 1990, then Canada, United States, and elsewhere from the 1990s. Singapore provided extensive research since 1959 and is considered a population laboratory to explore ethnic variations in the epidemiologic transition.11 Singapore is a small multiethnic stable island state with rapid economic development since 1959 and similar ethnic composition of Chinese, Malays, South Asians, and Europeans since, allowing comparison in a roughly controlled environment. Despite health programs and modernization producing annual CHD mortality declines from 1991 to 1999, the CVD incidence and survival rate difference remained for Indians, Malays, and Chinese.12

South Asians, like many ethnic communities, are prone to CVD and diabetes, with 50% to 300% higher CVD incidence and mortality, CHD 5 to 10 years earlier and a more progressive course.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 This consistent pattern emerges despite diversity of origins, culture, customs, socioeconomic state, changing environments, and differing adaptation and assimilation.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 South Asians develop diabetes younger and with lower body mass index and waist size.7 One Canadian study shows they present to hospital later, with more anterior myocardial infarction and more significant left main, multivessel, and distal coronary artery disease.8 There is diversity in South Asian and ethnic subpopulations, with differing risk and disease patterns, including many without premature CVD. Socioeconomic risk is complex, with professionals, physicians, and the middle class, a large segment of the US South Asian population, also at high risk. Smoking is also complex for South Asians, with high rates, but lower rates on migration for some groups and low rates in women in some countries.

The increased risk for South Asians reflects an adverse combination of gene-environment interactions on migration. It emerges despite similar or lower prevalence of traditional risk factors reported in many studies but attributed mostly to higher levels of 9 common risk factors in South Asian countries in the INTERHEART study.4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 Risk factors increase with urbanization or migration, producing a “typical pattern” of insulin resistance, prediabetes particularly impaired glucose tolerance, diabetes, abdominal obesity, metabolic syndrome, low high-density lipoprotein, high triglyceride, increased low-density lipoprotein, and hypertension.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 South Asian culture encourages overconsumption of high salt, saturated fat and high glycemic index foods, and reduced exercise, with social, cultural, and other barriers to change.

Other explanations include “thrifty gene” hypothesis with efficient storage of calories in times of want but risk in an environment of plenty, programming related to intrauterine growth and low birth weight, “genetic component” from high prevalence of disease genes and gene products, maternal hypercholesterolemia, adipose tissue hypothesis of smaller subcutaneous fat compartment and more visceral abdominal fat, mitochondrial and biochemical differences, maladaptation, stress, and social factors from migration.6, 7

Hidden risks and clustering of the “typical risk factors,” with multiplicative or nonlinear effects, explain some of the amplified risk and more severe and premature disease in South Asians.6, 7 South Asians have more glucose metabolic abnormalities for similar glucose levels, more abdominal visceral fat and insulin resistance despite “ideal” body mass index, and increased risk for diabetes starting young.6, 7, 8 One study from Singapore shows that when South Asians develop diabetes, the risk for CHD is higher compared to Chinese and Malays.13 The interaction of higher levels of emerging and thrombogenic risk factors found in South Asians, such as homocysteine, Lipoprotein(a), and others, with the “typical” lipid abnormalities, produce greater multiplicative effects.6, 7

Reducing excess risk in South Asians requires multilevel, positive, mainstream, and targeted measures using multiple approaches. These should address awareness, access, services, discrimination, cultural sensitivity, and biologic factors, modified for different countries, situations, and contexts.6, 7, 9 The Indo-US Healthcare Summit 2008 provides comprehensive, detailed, and practical recommendations, advocating primordial, primary, and secondary prevention by government, medical communities, the public, industry, and the media.7 Policy, grassroot change, and community building should encourage healthy living at all ages and remove barriers. Population screening, awareness, and change should start early and tap community strengths, such as social and cultural occasions. Treatment and risk reduction should be more aggressive, with risk scores modified for ethnicity, or ethnic specific tables used. Family history of premature CVD should be considered high risk and lower World Health Organization targets for waist circumference and waist-hip ratio adopted.6, 7

Innovative ideas and successful initiatives should be shared and replicated or scaled up. Examples include the Expecting Success program in the United States, demonstrating improved care after myocardial infarction and congestive heart failure, and Kush Dil (happy heart) in Edinburgh, improving risk factor profile for CVD. In Canada, a complex systems dynamic approach was used for health promotion, framing ethnicity and health as a “wicked problem.”6, 19, 20 Chronic disease initiatives should reduce disparities in health by addressing socioeconomic factors. New thinking on behavior, cognition, neuroscience of choice, and innovation and creativity in management, collaboration and change, especially using the Web, new media, and social networks, should be harnessed for health for ethnic and minority communities.

The experience of migrant ethnic populations has global implications. South Asians, 1.4 billion globally, will soon account for most of the world's heart disease with 50% of coronary artery disease deaths before age 50 by 2015 compared to 7% in the United States now, with CVD increasing steadily in China and in other emerging economies.7 Research on South Asians and Chinese abroad can guide health strategies for India and China, two fifths of world population, and the converse. Ethnic communities share more in disease causation than their differences, affirming the value of race, ethnicity, and health research for medicine, health, and all of humanity.17

Fifty years after the publication by Danaraj, racial and ethnic disparities in health remain. A World Health Organization editorial proposes addressing all systematic disparities, including race and ethnicity, as a new approach to public policy on tackling health inequalities and today's most far-reaching health policy challenge.21 Ethnic diversity is a new challenge for preventive cardiology and a health care equity and quality issue, with CVD accounting for most deaths globally.16, 17 Eliminating racial and ethnic disparities in health and making all communities healthy becomes a challenge for cardiology for the 21st century.

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Acknowledgements 

We thank Professor Raj Bhopal, Edinburgh, for valuable advice and manuscript review and Professor Srinath Reddy, New Delhi, for inspiration and advice. Suggested online resources: South Asian Health Foundation, South Asian Heart Center, http://www.healthy-india.org, http://www.femmefractal.com/tsunami.htm, and others. Correspondence: Dr Vivian S. Rambihar, The Scarborough Hospital, 3050 Lawrence E, Toronto, Ontario, Canada. M1P2V5. Email vivian.rambihar@utoronto.ca.

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References 

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PII: S0002-8703(09)00816-3

doi:10.1016/j.ahj.2009.10.020

American Heart Journal
Volume 159, Issue 1 , Pages 1-14, January 2010

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