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Why South Asians are at a greater risk of heart disease than other ethnic groups
By Suman Guha Mozumder
Feb 26, 2019 (PDF Link)
On a flight home from Mexico a couple of years ago, Silicon Valley-based academic and entrepreneur Vivek Wadhwa felt a shooting pain in his left arm.
Wadhwa, then 45, did not feel much concerned as he had never been sick in a decade, but on arrival when he went to the University of North Carolina Medical Center for a checkup, he learnt he suffered a heart attack and needed two stents in his arteries.
Fortunately for Wadhwa, the Indian-American Distinguished Fellow and professor at Carnegie Mellon University Engineering, Silicon Valley, the sudden pain passed without any serious incident.
Another IT professional from Southern India, identified by researchers by his first name Sundar, suffered a sudden chest pain and a heart attack a few years ago in Illinois, although the 42-year old vegetarian did not have the typical profile of a high-risk candidate for heart disease: he weighed about 150 pounds, had a Body Mass Index (BMI) of 25, earlier classified as a healthy weight in an individual, was a nonsmoker and did workouts regularly.
Sundar also survived the heart attack, but experts say incidents like the one experienced by people like Wadhwa and Sundar are not at all uncommon in the South Asian community in the U.S., where almost everyone knows somebody among their friends and relatives who have died of some cardiovascular disease or suffered a heart attack or a stroke.
Experts have known for years that South Asians have an increased chance of developing cardiovascular disease, but the problem is that in the absence of any scientific research focused exclusively on the community, it has remained somewhat of a mystery as to why South Asians have a higher burden of cardiovascular risk factors at younger ages.
According to experts, South Asians have a higher risk of myocardialinfarction and higher proportionate mortality from
cardiovascular disease compared with most other race/ethnic groups in the United States. These experts admit that although Indian-Americans do not usually fit the typical profile of someone vulnerable to heart attacks or other major heart-related ailments, they have an increased chance of developing cardiovascular diseases and suffer a higher death rate than any other ethnic group.
Traditionally, South Asians’ preference for oil-rich food with lots of refined carbohydrate and high sugar consumption have been blamed for many an illness, including diabetes and heart diseases, but experts say such food habits alone may not be adequate to explain the reason for high incidence of cardiovascular disease among South Asians.
The American Heart Association noted in 2018 that South Asians living in the U.S. are more likely to die from heart disease than the general population, but this risk, it said, has been largely hidden by a lack of data.
To understand this issue better and study the issue in greater depth as to why South Asians — people from India, Pakistan, Bangladesh, Sri Lanka, Nepal, Bhutan and the Maldives — are at a greater risk for heart disease than other ethnic groups, and why they are four times more vulnerable to cardiac disease than the general population, a group of researchers has embarked on a research study on the subject since 2010.
This long-term research study has received substantial funding from the National Institutes of Health and is led by Alka Kanaya of the University of California, San Francisco and Namratha Kandula of Northwestern University in Chicago, the two co-principal investigators of the first-of-its-kind study on heart disease among South Asians in the U.S.
The idea is to find out the reasons for the high prevalence of heart diseases among South Asians, and if there are risk factors that are different than those found in the general population. The goal of the study is to generate new knowledge to improve the prevention and treatment of heart disease in South Asians.
The research study which is known by its acronym MASALA (Mediators of Atherosclerosis in South Asians Living in America), is being conducted in a population-based sample of 1164 South Asian men and women aged 40–84 years at the two university clinical field centers in San Francisco and Chicago.
“This is really a puzzle — why south Asians have higher rates of heart diseases compared to other racial and ethnic groups — and that is exactly why we are doing this study because no one seems to have an answer to that puzzle,” Kanaya, Associate Professor of Medicine in the Division of General Internal Medicine at UCSF, who is the research study’s co-principal investigator along with Kandula, told India Abroad.
The importance of the study lies in the fact that heart disease is the number one cause of death worldwide and accounts for 30 percent of all deaths.
South Asians comprise 60 percent of the world’s heart disease patients. South Asians have the highest death rate from heart disease in the United States compared to other ethnic groups. Studies from around the world have also shown that South Asians have a higher burden of cardiovascular risk factors at younger ages.
According to American Heart Association, there are around 3.4 million people of South Asian descent living in the U.S. as of 2010, based on the U.S. Census Bureau data.
Despite their numbers, the threats to South Asians’ cardiovascular health have been obscured because researchers have been looking at Asian-Americans as a monolithic group. When examined individually, South Asians have a higher risk of heart disease than other Asian groups, especially East Asians from China, Japan and Korea, according to the American Heart Association.
Studies of Japanese, Latinos and other groups have usually found that adapting to a Western culture increases rates of diabetes, high blood pressure or other risk factors for heart disease.
But MASALA’s participants reveal a different trend. The process of acculturation may be different for South Asians.
In 2017 Congresswoman Pramila Jayapal (D-Wash.) announced the introduction of the South Asian Heart Health Awareness and Research Act. The bipartisan bill, co-sponsored by Rep. Joe Wilson (R-S.C.), sought to raise awareness of the alarming rate at which the South Asian community was developing heart disease and to invest in ways to reverse this trend.
It also sought to include a Sense of Congress that U.S. medical schools should include as part of their nutrition curriculum, a focus on South Asian diet and ways to achieve optimal nutrition in these populations.
The bill also sought to create South Asian Heart Health Promotion Grants at the Centers for Disease Control to develop a clearing house and web portal of information on South Asian heart health and to develop culturally appropriate materials to promote heart health in the community and provide grants to work with community groups involved in South Asian heart health promotion.
“I would say that we have some clues to the puzzle, but we haven’t completely solved the puzzle as yet, and one of the first clues is the fact that South Asians have a lot of fat inside the body around the abdominal area, in the liver and around the heart,” Kandula, the other principal investigator for the MASALA study, who is associate professor of Medicine (General Internal Medicine and Geriatrics) and Preventive Medicine, told India Abroad.
Both Kandula and Kanaya said that even though the South Asians have a low body mass index, they tend to accumulate a lot of fat in certain parts of the body like the abdominal area that causes different types of inflammation and activate certain biological pathways that contribute to Atherosclerosis or hardening of arteries. “I definitely think this is an important contribution of our MASALA study and extends what we know about heart disease,” Kandula said.
The MASALA study is modelled on the 2001 Multi-Ethnic Study of Atherosclerosis (MESA), involving more than 6,000 men and women from six communities in the United States, including Chinese, Latino, Black and White and it has also learned from the Framingham Heart Study, a long-term, ongoing cardiovascular cohort study on White males of Framingham, Massachusetts that started in 1948 with 5,209 adult subjects.
But MASALA researchers said that none of the earlier studies in the U.S. had focused on South Asians and therefore, there is very little data available about the unique cardiovascular issues relating to South Asians.
Thanks to new information based among others on MASALA research, the American College of Cardiology, American Heart Association and 10 other health organizations, have issued new guidelines in November last year, stressing how race and specific ethnic characteristics may influence a person’s risk of developing cardiovascular diseases.
The guidelines also made clear distinctions among different Asian ethnicities, noting that people of South Asian descent have “a higher risk” of developing heart disease than the general American population.
“Everybody’s looking for a simple explanation, like it’s the diet or because people don’t exercise, because people are too stressed out, but the higher risk for heart disease in South Asians is most likely the result of several different factors acting together,” Kandula said. “So, there may be the genetic predisposition that is exacerbated by certain environmental factors and that can be made worse by stress or poor diet. We are thinking about how different factors interact to cause disease, and not just a single variable explaining this problem,” she said.
Similarly, Kanaya said the researchers are looking at all different factors, including genetics and epigenetics, dietary and physical factors and things like discrimination, psychological stress and depression and anxiety. “You can say we have a holistic approach and are taking a lot of things into consideration to understand this puzzle,” Kanaya told this correspondent. “We are taking a deep dive into South Asians cardiovascular health,” Kanaya said.
But she and Kandula emphasized the need to continue the study and follow participants over time, which will require longterm commitment from participants and continued funding “It is a relatively young study, started 10 years ago, and we need to follow people for at least 10 more years to find more definitive answers about the true incidence of heart disease in the U.S. South Asian community,” Kanaya told this correspondent.
According to the MASALA researchers, the same group of cohorts, some 1164 South Asian men and women, most of them from India but also from Pakistan and other countries — come every couple of years to the two clinical research centers in San Francisco and Chicago where various medical tests and blood work are done on them to monitor their health.
To begin with, the cohorts have to be South Asians, living permanently in the U.S and having no heart condition, meaning they have not been diagnosed with heart problems or and undergone any cardiac procedure done on them.
“We follow these healthy, middle-aged South Asians and we monitor them to find out if they develop any heart related issues over time, and if they do, we try to understand why it could have happened.
“And if someone stays healthy, that is also useful information because we can try to understand what are the factors that keep South Asians healthy, and free of heart disease” Kanaya said. The participants come for five hours of testing that includes CT scans of the heart, the abdomen and ultrasound of the neck arteries as well as EKGs, followed by blood samples.
“We keep the blood samples since we also want to do genetic studies,” Kanaya said.
Besides the fact that both the principal investigators are interested in the science of South Asians cardiovascular diseases they also have personal reasons to be committed to heart heath care. “My grandfather died of heart attack in India at the age of 56, and I grew up with his story, and I have always wondered why my grandfather died at a young age,” Kandula said.
“This is why I am passionate about the issue, and as an immigrant, I am committed to improving healthcare in the U.S. for immigrant communities.”
“We all have someone in our first-degree circle that has either died suddenly or had premature cardiovascular disease,” said one researcher.
By Anahad OʼConnor
Feb. 12, 2019
Mahendra Agrawal never imagined he would have a heart attack. He followed a vegetarian diet, exercised regularly and maintained a healthy weight. His blood pressure and cholesterol levels were normal.
But when Mr. Agrawal experienced shortness of breath in June 2013, his wife urged him to go to a hospital. There, tests revealed that Mr. Agrawal, who was 63 at the time, had two obstructed coronary arteries choking off blood flow to his heart, requiring multiple stents to open them.
“I’m a pretty active guy and I eat very healthy, my wife makes sure of that,” said Mr. Agrawal, who lives in San Jose and worked in the electronics industry. “It makes me wonder why this happened to me.”
Despite his good habits, there was one important risk factor Mr. Agrawal could not control: his South Asian ancestry. Heart disease is the leading killer of adults nationwide, and South Asians, the second fastest-growing ethnic group in America, have a higher death rate from the disease than any other ethnic group. People of South Asian descent, which includes countries like India, Pakistan, Bangladesh, Nepal, Sri Lanka, Bhutan and the Maldives, have four times the risk of heart disease compared to the general population, and they develop the disease up to a decade earlier.
“Every South Asian has a very common experience unfortunately, and it’s that we all have someone in our first-degree circle that has either died suddenly or had premature cardiovascular disease,” said Dr. Abha Khandelwal, a cardiologist at the Stanford South Asian Translational Heart Initiative.
Experts are only now beginning to uncover why rates of heart disease are so high in this group. For the last seven years, a team of researchers at the University of California, San Francisco and Northwestern University has followed more than 900 South Asians in Chicago and the Bay Area. Their ongoing study, known as Masala, for Mediators of Atherosclerosis in South Asians Living in America, has found that South Asians tend to develop high blood pressure, high triglycerides, abnormal cholesterol and Type 2 diabetes at lower body weights than other groups. South Asian men are also prone to high levels of coronary artery calcium, a marker of atherosclerosis that can be an early harbinger of future heart attacks and strokes.
“South Asians represent almost 20 to 25 percent of the world’s population, and this is a major public health problem in this huge population,” said Dr. Alka Kanaya, a professor of medicine at U.C.S.F. and one of the Masala principal investigators. Born in Mumbai and raised in California, Dr. Kanaya was inspired to launch the Masala project after seeing many of her friends and family members die from heart disease at relatively young ages.
In November, the American Heart Association and other medical groups issued updated cholesterol guidelines that, for the first time, urged doctors to consider ethnicity when determining a patient’s cardiovascular risk and treatment options. Citing studies by the Masala researchers, the guidelines identified South Asians as a “high risk” group and “stronger candidates” for statin medications when other risk factors are present.
Some of the most striking findings to come out of Masala relate to body composition. Using CT scans, Dr. Kanaya and her colleagues found that South Asians have a greater tendency to store body fat in places where it shouldn’t be, like the liver, abdomen and muscles. Fat that accumulates in these areas, known as visceral or ectopic fat, causes greater metabolic damage than fat that is stored just underneath the skin, known as subcutaneous fat.
Studies show that at a normal body weight — generally considered a body mass index, or B.M.I., below 25 — people of any Asian ancestry, including those who are Chinese, Filipino and Japanese, have a greater likelihood of carrying this dangerous type of fat.
Despite having lower obesity rates than whites, Asian-Americans have twice the prevalence of Type 2 diabetes, which promotes heart attacks and strokes.
Heart risks tended to be greatest in South Asians, the Masala researchers found. In one recent study, in the Annals of Internal Medicine, they found that 44 percent of the normal weight South Asians they examined had two or more metabolic abnormalities, like high blood sugar, high triglycerides, hypertension or low HDL cholesterol, compared to just 21 percent of whites who were normal weight.
The Masala researchers also found that using the standard cutoff point to screen for diabetes, a B.M.I. of 25 or greater, would cause doctors to overlook up to a third of South Asians who have the disease. “Many of them may never get to that B.M.I. and they will have had diabetes for years,” Dr. Kanaya said.
The findings helped prompt the American Diabetes Association to issue updated guidelines in 2015 that lowered their screening threshold for diabetes, to a B.M.I. of 23 for Asian-Americans. A public awareness campaign, organized by the National Council of Asian Pacific Islander Physicians, called Screen at 23 has drawn attention to the issue, and a.t least three states, including California, Massachusetts and Hawaii, have enacted policies to promote more aggressive health screenings of Asian-Americans. Representative Pramila Jayapal of Washington, the first Indian-American woman to serve in the House, recently introduced a bill to provide more funding for South Asian heart health awareness and research.
Most of the participants in the Masala study are first-generation immigrants, and the researchers found that their cultural practices also impact their disease rates. Cardiovascular risks tended to be highest in two groups: those who maintained very strong ties to traditional South Asian religious, cultural and dietary customs, and those who vigorously — embraced a Western lifestyle. Those with lower risk are what the researchers call bicultural, maintaining some aspects of traditional South Asian culture while also adopting some healthy Western habits.
This discrepancy plays out in their dietary behaviors. Almost 40 percent of Masala participants are vegetarian, a common practice in India that is widely regarded in the West as heart healthy. But vegetarians who eat traditional South Asian foods like fried snacks, sweetened beverages and high-fat dairy products were found to have worse cardiovascular health than those who eat what the researchers call a “prudent” diet with more fruits, vegetables, nuts, beans and whole grains (and, for nonvegetarians, fish and chicken). People who eat a Western style diet with red and processed meat, alcohol, refined carbohydrates and few fruits and vegetables were also found to have more metabolic risk factors.
Dr. Namratha Kandula, a Masala investigator at Northwestern, said she hopes to study the children of the Masala participants next because they tend to influence their parents’ health and lifestyle habits, and the researchers want to understand whether health risks in second-generation South Asians are similar or not. But for now, some experts say their goal is to increase outreach to South Asians who may be at high risk and neglecting their health.
“As a South Asian Bay Area resident, I see that we focus a lot on success and academic achievements in our families,” said Dr. Khandelwal at Stanford. “But we don’t necessarily look at our health success, and your health is something that you can’t easily get back.”
Anahad OʼConnor is a staff reporter covering health, science, nutrition and other topics. He is also a bestselling author of consumer health books such as “Never Shower in a Thunderstorm” and “The 10 Things You Need to Eat.”