Heart Disease among Indian Americans
- The US population is an amalgam of immigrants from virtually all countries and cultures in the world. Unlike in other countries, where Indians tend to congregate in selected pockets in the country, the 3.2 million Indians in the US are spread over a land area three times larger than India itself. The Indian population in the US grew 68% in the last decade. (2010 census)
- The government bears no responsibility for the health care and patients are at liberty to receive medical care from any physician anywhere in the US (if he/she can afford it directly or indirectly through health insurance). Furthermore, Indians are highly reluctant to participate in research for fear for of the researchers knowing the health information of the individuals.
- These unique features make it extremely difficult to study the incidence, prevalence, and mortality from CAD (coronary artery disease) and explain why the US was the last country to report an excess burden of CAD among the Indians.
- In the US, Asian Indians comprise 85% of the South Asians and enjoy a higher socioeconomic status than other Americans, by virtue of a very high proportion of professionals, especially physicians.1 Many of them have made maximum modification of lifestyle and have a low prevalence of conventional risk factors compared to the general population of the US.
- The Coronary Artery Disease among Asian Indians (CADI) Study was the first systematic investigation of CAD among Asian Indians in the US. The age-adjusted prevalence of CAD among men was 10% in the CADI Study compared to 2.5% in the Framingham Offspring Study ─ generally considered a standard sample of the US population.2
- More than half of the Asian Indians are lifelong vegetarians. Unlike other populations, heart disease rates are equally high among vegetarians and non-vegetarians.2 Vegetarians, compared to non- vegetarians, had similar levels of lipids but higher levels of diabetes.3 The prevalence of CAD was even higher for men (12%) in another small study.4 Women participants were few and young and had a lower rate.2
- The high rates of CAD in Asian Indians in the US are not limited to physicians. In a large study of 13,537 Americans in California, the rate of hospitalization from CAD among Asian Indians was four times higher than in whites and six times higher than in Chinese (Figure 009).5 The rates for Japanese, Filipinos, and other Asians were no different than whites.5 Thus, Chinese and Asian Indians are at the opposite extremes with regard to heart disease.5
- The 4-fold prevalence of CAD among Asian Indians in the US is higher than the rates reported from other countries.
- The high risk of CAD among Asian Indians is often missed because they are included among the 10 million Asian Americans who have low rates of CAD in the national data.6 7
- Although national mortality data for Asian Indians in the US are not yet available, standardized mortality ratios (SMR) and proportional mortality ratios (PMR) for CAD in the state of California have been reported and have given some insights. The PMR was highest for Asian Indians and women, when compared with 6 other ethnic groups.8 With 100 as the standard, the SMR for CAD was 120 and PMR was 350 in Asian Indian men 25-44 years of age. Again, with 100 as the standard, the SMR for CAD was 130 and PMR was 220 for women 45-64 years of age.9 Both these numbers indicate the high degree of premature CAD deaths in Indians in the US as is observed around the world.8
- CAD is the leading cause of deaths in Asian Indians in California accounting for 32% of deaths in women and 39% in men.10 The proportion of deaths from CAD increased with age in both genders. For men, it increased from 17% in those younger than 45 years of age to 43% in those aged 45-64 years to 44% in those older than 65. The corresponding figures for women were 3%, 25%, and 41% respectively.10
- CAD accounted for about 89% of CVD (cardiovascular disease) deaths in men of all age groups and over 84% of the CVD deaths in women aged >65 years.1 CAD claimed 5 times more deaths than from stroke, 7-12 times more deaths than diabetes, and 2 times more than cancer in women and 5 times more than cancer in men.10
- Unlike in the UK, where stroke mortality is substantially higher than whites, Asian Indians in the US have a very low stroke mortality accounting for only 5% of all deaths in men and 6% in women.10, 11
- Recent reports suggest that Asian Indians have the highest life expectancy of all Asian subgroups in California, which may represent a healthy migrant effect, salmon effect, or very low rates of competing causes like cancer.12
- The excess morbidity and mortality from CAD among Asian Indians in the US is consistent with the pattern seen in Indian Diasporas throughout the world. But the excess incidence and prevalence of CAD among Asian Indians in the US are considerably higher than that in Diasporas in other countries.
- Whereas the prevalence of traditional risk factors are similar or lower, Asian Indians have an excess of all emerging risk factors such as high levels of lipoprotein(a), homocysteine and high total/HDL ratio. High prevalence of prediabetes and overt diabetes may have a synergistic effect on the conventional and emerging risk factors.13, 14.
- The high rates of CAD in Asian Indians is due to a combination of nature (genetic predisposition) and nurture (lifestyle factors).15 The nature is attributed to elevated levels of lipoprotein(a). Given this genetic predisposition, the harmful effects of traditional modifiable risk factors related to lifestyle as well as the emerging risk factors are magnified.
1. Palaniappan L P, Araneta MR, Assimes TL, et al. Call to action: cardiovascular disease in Asian Americans: a science advisory from the American Heart Association. Circulation. Sep 21 2010;122(12):1242-1252.
2. Enas EA, Garg A, Davidson MA, Nair VM, Huet BA, Yusuf S. Coronary heart disease and its risk factors in first-generation immigrant Asian Indians to the United States of America. Indian Heart J. Jul-Aug 1996;48(4):343-353.
3. Chuang CZ, Subramaniam PN, LeGardeur BY, Lopez A. Risk factors for coronary artery disease and levels of lipoprotein(a) and fat-soluble antioxidant vitamins in Asian Indians of USA. Indian Heart J. 1998;50(3):285-291.
4. Mooteri SN, Petersen F, Dagubati R, Pai RG. Duration of residence in the United States as a new risk factor for coronary artery disease (The Konkani Heart Study). Am J Cardiol. Feb 1 2004;93(3):359-361.
5. Klatsky AL, Tekawa I, Armstrong MA, Sidney S. The risk of hospitalization for ischemic heart disease among Asian Americans in northern California. Am J Public Health. Oct 1994;84(10):1672-1675.
6. Jha P, Enas E, Yusuf S. Coronary Artery Disease in Asian Indians: Prevalence and Risk Factors. Asian Am Pac Isl J Health. Autumn 1993;1(2):163-175.
7. Enas E A. Cardiovascular Diseases in Asian Americans and Pacific Islanders. Asian Am Pac Isl J Health. Winter 1996;4(1-3):119-120.
8. Wild SH, Laws A, Fortmann SP, Varady AN, Byrne CD. Mortality from coronary heart disease and stroke for six ethnic groups in California, 1985 to 1990. Ann Epidemiol. 1995;5(6):432-439.
9. Palaniappan L, Wang Y, Fortmann SP. Coronary heart disease mortality for six ethnic groups in California, 1990-2000. Ann Epidemiol. Aug 2004;14(7):499-506.
10. Palaniappan L, Mukherjea A, Holland A, Ivey SL. Leading causes of mortality of Asian Indians in California. Ethn Dis. Winter 2010;20(1):53-57.
11. Wild SH, McKeigue P. Cross sectional analysis of mortality by country of birth in England and Wales, 1970-92. Bmj. 1997;314(7082):705-710.
12. Razum O, Zeeb H, Rohrmann S. The ‘healthy migrant effect’–not merely a fallacy of inaccurate denominator figures. Int J Epidemiol. Feb 2000;29(1):191-192.
13. Enas EA. Coronary artery disease epidemic in Indians: a cause for alarm and call for action. J Indian Med Assoc. Nov 2000;98(11):694-695, 697-702.
14. Enas EA, Dhawan J, Petkar S. Coronary artery disease in Asian Indians: lessons learnt and the role of lipoprotein(a). Indian Heart J. Jan-Feb 1997;49(1):25-34.
15. Enas EA. How to Beat the Heart Disease Epidemic among South Asians: A Prevention and Management Guide for Asian Indians and their Doctors. Downers Grove: Advanced Heart Lipid Clinic USA; 2011.