The MASALA Study Is Helping Doctors Understand Why South Asians Are Uniquely Vulnerable to Heart Disease 

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Are race and ethnicity risk factors for developing heart disease? According to the American Heart Association, yes. In 2018, the organization added race and ethnicity as factors in its high cholesterol risk guidelines, drawing attention to one overlooked health disparity in the process: Compared to the general United States population, South Asians have the highest risk of developing heart disease.

As part of the fastest-growing racial and ethnic group in the country, according to the 2020 census, South Asians are often lumped in with other Asian Americans despite major differences in income level, educational attainment, cultural norms, and health risks. The group’s ancestral roots lie in India, Pakistan, Bangladesh, Nepal, and Sri Lanka. Even among South Asians, religious and cultural practices widely differ from Hindu and Jain practitioners, many of whom adopt a vegetarian diet; to Muslims from across the subcontinent, who eschew pork.

Well before the AHA’s inclusion of race and ethnicity as a consideration in high cholesterol treatments, medical researchers have been studying how and why South Asians overall have an elevated risk of heart disease. Though research is still ongoing, scientists have discovered a mixture of biological and cultural factors influencing lifestyle habits—findings which may help lead to interventions that can help South Asians across the country stave off diabetes, heart disease, and stroke.

Since 2006, the Mediators of Atherosclerosis in South Asians Living in America (MASALA) Study has followed more than 900 South Asians in Chicago and the Bay Area. Researchers look at how lifestyle habits, social and cultural norms, and possible biological differences drive the development of heart disease and related conditions like diabetes and metabolic syndrome.

Run by researchers at Northwestern University and University of California, San Francisco, the still-ongoing MASALA Study has teased out South Asians’ unique health risks from other Asians and uncovered some startling statistics about the group. Compared to the overall U.S. population, South Asian Americans are four times more likely to develop heart disease. They also have a higher probability of heart attacks before the age of 50, and the highest prevalence of Type 2 diabetes, a major contributor to heart disease.

Compared to the overall U.S. population, South Asian Americans are four times more likely to develop heart disease.

Alka Kanaya, MD, the project’s principal investigator and an internist at UCSF, says that existing public health research on South Asians living in Singapore and other parts of the Western world, as well as her own personal awareness of diabetes and heart disease among family members, are what drove her to begin the MASALA Study. “Before that, there was really no existing data in the United States about this,” Dr. Kanaya says. “It’s really hard to see any of the nuances when you aggregate 40 very diverse cultural groups together.” Today, the study has expanded to include an additional 250 subjects, and hopes to add more Pakistani and Bangladeshi patients to the study. (Currently, the study is composed of 83 percent Indian Americans.)

Among other important findings, MASALA has also uncovered a relationship in South Asians between body composition and diabetes. Through CT scans, Dr. Kanaya’s team has found that the group has a tendency to store visceral fat, or fat found in and around the liver, intestines, and abdomen. This tendency towards abdominal fat is also found in other Asian ethnic groups.

As a collective group, Asian Americans have a lower risk of dying from heart disease, but South Asians actually have higher mortality risk than non-Hispanic whites and other Asian groups once East and Southeast Asian population health data is factored out. The reasons, both biological and sociocultural, for this increased risk are difficult to pin down, according to Abha Khandelwal, MD, a cardiologist and researcher at the Stanford South Asian Translational Heart Initiative.

“Part of the reason it's very difficult to truly understand cardiovascular disease in South Asians is that it's such a heterogeneous group of patients,” Dr. Khandelwal says, referring to both genetics and lifestyle behaviors shaped by cultural practices and norms. However, she adds that dietary practices are a large contributor, and that there is evidence that South Asians tend to have higher levels of lipoprotein A, a type of cholesterol particle which increases heart disease risk.

By and large, however, Khandelwal says hypertension and diabetes, both of which contribute to heart disease, are still globally quite prevalent in South Asians. Some of that is attributable to a vegetarian diet rich in processed starches and fried foods. (Although many South Asians, for religious and cultural reasons, eat a vegetarian diet, not all do.)

Internist Ronesh Sinha, MD, wrote The South Asian Health Solution in 2015 after realizing that the standard health guidelines most primary care doctors gave to high risk South Asian patients weren’t aligning with their culturally informed eating habits. A lot of South Asians may fly under the radar because they may lack subcutaneous fat, which can contribute to looking visibly overweight, he adds. Instead, they have hidden visceral fat, which the MASALA Study has also identified, and often lack muscle mass. Visceral fat, which typically wraps around organs, is associated with a higher risk of heart disease. “Weight is pretty misleading—for all ethnic groups,” Dr. Sinha says. Instead, he focuses more on waist circumference, or waist-to-height ratio. “If you take your height and you divide it by two, your waist circumference should really be at that number or below.”

“Weight is pretty misleading—for all ethnic groups." —Ronesh Sinha, MD

South Asians are also more likely to contract diabetes or metabolic syndrome, a pre-diabetic condition, at a lower body weight than the rest of the population, which is what contributed to the American Diabetic Association recommending lowering the BMI cutoff for Asian Americans in measuring diabetes risk in 2015, which Dr. Kanaya helped co-author. In midlife, Sinha himself developed metabolic syndrome, a collection of symptoms that signal insulin resistance, or the first signs of diabetes. “Seeing young patients come in [with early heart disease and diabetes] and then watching myself, in parallel, develop some of these risk factors was an eye-opening experience,” Dr. Sinha says.

Although a large percentage of Indian Americans (who make up the majority of the United States’ South Asian population) eat a vegetarian diet, it’s not necessarily healthy, he adds. Compared to a vegetable-rich Western vegetarian diet, a South Asian vegetarian diet might be more grain-focused, with a lot of flatbreads, fried snacks, and large servings of rice and starchy vegetables. In his practice, Dr. Sinha recommends his vegetarian South Asian patients integrate more plant-based protein sources and cut back on carbohydrates. “They can still enjoy their carbohydrates, but they just have to be conscious of the amount that they're consuming,” he says.

Overall, Dr. Kanaya, the MASALA Study’s lead researcher, hesitates to point the finger at any biological factors driving this disparity in heart disease and diabetes. Instead, she emphasizes cultural and social determinants, including adherence to traditional culture versus assimilation. Among South Asian women, the MASALA Study has found that women who had more Westernized cultural attitudes had fewer heart disease risk factors. “That’s completely different from what's been seen in other immigrant groups,” Dr. Kanaya says, citing evidence on Japanese Americans, who have seen higher rates of obesity, heart disease, and diabetes with each passing generation and increasing assimilation. Part of this is based on diet, but part may also be chalked up to fewer cultural beliefs that promote regular physical activity. “Things may be changing now in younger generations, because they’re exposed to messaging that it’s better to be physically active, versus a culture that has never promoted physical activity as important,” Dr. Kanaya says.

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