Preventive Cardiology for Asian Americans

It is well-documented that chronic diseases, such as cardiovascular disease (CVD), manifest differently in different ethnic groups. Due to rapidly increasing numbers of immigrants from Asian countries (Table 1), the extent of, and reasons for, such differences, have revived clinical as well as social justice interests in Asian Americans as one of the fastest growing racial groups in the U.S. The number of Asian Americans, at 13.5 million in 2003 and consisting of 60% immigrants, is expected to double by 2025, and reach almost 36 million by 2050 (Table 2). Cardiovascular disease (CVD), combining heart disease and stroke, remains as the leading cause of death in this group as it had over the past several decades. A higher incidence of stroke in Asian Americans, when compared with Caucasian Americans, has also been noticed with alarming concern1. In the Healthy People 2010 initiative, CVD is one of the six targeted health areas for Asian Americans. There is need for more ethnic specific data in order to quantify, qualify, and improve on the cardiovascular status of Asian Americans 2.

This knowledge deficit has been recognized by leading clinical and research experts in the cardiovascular areas as a dire need in the American healthcare system. Recently, there have been some concerted efforts by the U.S. National Heart, Lung, and Blood Institute (NHLBI) of the National Institute of Health (NIH) and the Centers for Disease Control and Prevention (CDC) to do prevention and manage cardiovascular risk factors, but much work remains to be done 3. The Heart Disease and Stroke Statistics – 2005 Update, a recognized statistical source of cardiovascular information in the U.S. and a joint publication of the American Heart Association and the American Stroke Association, does not contain a summary CVD and risk data on Asian Americans 4.

Asian Americans are a diverse racial group, consisting of people from over 20 different countries with over 100 different languages, collectively put together for statistical convenience but without consideration of clinical relevance. Meaningful data can, can become even more useful in clinical management for physicians when this group can be studied and yield data in a desegregated fashion.5. The Honolulu Heart Program (HHP) was probably an exemplary effort to study the risk factors of heart disease, from 1991 to 1993, in elderly Japanese-American men who were free of overt CVD at the time of enrollment into the study. Several articles on various important aspects of CVD and its risk factors have been published from the work of HHP and others, and as a result, more detailed knowledge about cardiovascular disease in Japanese Americans in Hawaii is known today than any other Asian subgroups in the U.S. Japanese are the 6th largest Asian subgroup by size (Table 1).

CVD Risk Factor Profiles of Asian Americans

Because CVD is a complex disease with an interplay of genetic, behavioral, psychosocial, and environmental factors, the CVD risk profiles for Asian Americans, which is composed of a large percentage of immigrants from different Asian cultural and language backgrounds, present a different composite inter- and intra-racially. The following is a summary of findings of Asian American’s CVD risk profiles presented in recent literature. These findings need to be interpreted with caution, as the majority of these studies have small numbers of subjects in the samples, most of which are convenient samples. Most of them are cross-sectional studies that have no comparison studies to check for data reliability.

Asian Americans

Heart disease was the leading cause of death for Asian men and women in 1980. When combined with stroke, the third leading cause of death, CVD remains as the top killer in Asian Americans. Smoking and hypertension are regarded as the two most important preventable risk factors for Asian Americans. English proficiency was found to be inversely associated with smoking in Asian males, in that males with a high English proficiency were found to smoke less, but the reverse was true for Asian women 6. Acculturation levels, on the other hand, had a direct association with smoking in Asian women, in that Asian women who were more acculturated tend to smoke more, and the opposite was true in Asian men 7. Coronary calcium scores were found to be similarly high for Asian American and Caucasian subjects at 60%, as compared with 36% of African American subjects 8. The metabolic syndrome, consisting of an aggregate of several risk factors (atherogenic dyslipidemia, hypertention, abdominal obesity, glucose intolerance or insulin resistance, prothrombotic state, and proinflammatory state), was roughly the same in the different Asian subgroups (33.4%), but higher than the white population 9. Asians also seemed to have smaller waist circumferences and require a separate measurement in the WHO criteria for obesity 10 .

Japanese Americans

Immigration and westernization were found to associate with an increase in cardiovascular risk factors such as hypercholesterolemia and triglyceride levels, insulin resistance, hypertension, microalbuminuria, waist-hip ratio, IMT and plague size 11-13. Japanese Americans were found to have a lower average blood pressure, with a higher treatment rate for hypertension, and a lower smoking prevalence, but higher body mass index, LDL, fibrinogen level 13, and carotid intima-media wall thickness (IMT), which was found to be significantly greater and developed quicker 14. In one study, the prevalence rates for hypertension were at 53% (ages 60 to 64), 59% (ages 65 to 74), and 67% (ages 75 to 81) 15. Japanese females (12.7%) were found to smoke more than females in other Asian subgroups 6. The ankle brachial index was found to be associated with CHD and can be used for risk assessment. Body mass index and sedentary lifestyle were found to have an association with two other CVD risk factors: elevated triglyceride and systolic blood pressure levels, possibly reflecting an insulin resistance syndrome 16. Lower levels of total cholesterol were found in older males and in those after bypass surgery or post stroke 17.

Filipino-Americans

Visceral adipose tissues (VAT) were found to be higher in Filipino women than white or black women 18, and a higher prevalence of hypertension and diabetes was found in Filipino-Americans as compared to Caucasians.

Asian Indian Americans

(from the Indian subcontinent)

Asian Indian Americans have a higher prevalence of dyslipidemia: low levels of HDL and elevated levels of triglycerides, Apolipoprotein A-1, and fibrinogen, high stress levels, hypertension, insulin resistance and diabetes, obesity, sedentary lifestyle, and an increased fat consumption, along with an associated higher incidence of coronary heart disease 19-23. Asian Indians have lower smoking rates overall when comparing within the Asian subgroups 6.

Chinese Americans

Chinese (both males, 59%, and females, 42%) have the second highest coronary calcification compared to other ethnic groups 24. Metabolic syndrome and diabetes are associated with an increased risk of aortic valve calcification 25. A subset of Chinese Americans in San Francisco showed a high prevalence rate of 69% in hypertension, with a low control rate of 14% 26. Tai Chi exercises were found to significantly reduce hypertension 27. Chinese Americans were found to have the lowest adjusted mean body mass index and smoking prevalence among the Asian subgroups 6. Stroke, especially hemorrhagic stroke, is a predominant cardiovascular mortality in the Chinese Americans 28.

Vietnamese Americans

In one study of hypertension in the Vietnamese Americans, it was found that nearly 44% of them are hypertensive, and there was a serious knowledge deficit in their understanding of hypertension as a chronic disease 29. Vietnamese Americans (1.1% of what population denominator) were found to smoke the least among the Asian subgroups6.

Korean Americans

In one study of elderly Korean Americans, they were found to have frequent risk factors hypertension (71%), hypercholesterolemia (53%), overweight (43%), sedentary lifestyle (24%), diabetes (18%), and smoking (7%) 30. Korean males 35.9% (29.2-42.6%) smoke more than males in the other Asian subgroups 6.

Discussion

Currently, huge data gaps exist for Asian Americans in areas of prevalence and incidence rates, both the primary and secondary prevention of CVD risk factors, cardiac rehabilitation, use of medications, and treatment compliance. Reliable national baseline data for Asians is still lagging despite the Healthy People 2010 project mandating outcome measurement.

Major challenges will remain ahead until appropriate adequate levels of funding exist for research as well as for public health programs to promote healthy lifestyle choices – diets high in fruits and vegetables, low in saturated fats and regular physical activity – for all Americans. Adding a consistent

Asian American component to the major national CVD database sources such as Get With the Guidelines (American Heart Association), the STS National Database (Society of Thoracic Surgeons), the National Registry for Myocardial Infarction (Genetech), the ACC-NCDR (American College of Cardiology), and the National Health and Nutritional Examination Survey (NHANES) will be useful to fill in the national health data gaps for the Asian American subgroups.

Table 1. Census 2000 data on major Asian subgroups in the U.S. by countries of birth

Asians (All 17 ethnic groups)	Chinese	Filipinos	Asian Indians	Korean	Vietnamese	Japanese	Cambodians
Number Counts in millions ( Asians in descending order, followed by NHOPI)
11.9	2.7	2.3	1.9	1.23	1.22	1.1	0.21

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