The MASALA Study Unpacks South Asians’ Heart and Metabolic Disease Risk

As a person of Indian origin, Alka Kanaya saw diabetes and heart disease wreak havoc in her family. As a general internist and physician scientist at the University of California, San Francisco (UCSF), Kanaya witnessed a similar trend. “It's very common to see a young South Asian man present with a heart attack in their thirties and forties, where you don't see that in other groups,” said Kanaya.

While South Asians make up about a quarter of the world’s population, they bear nearly 60 percent of the global burden of heart disease.¹ They are also more prone to diabetes compared to other ethnic groups.² Some hypotheses attribute these outcomes to insulin resistance, wherein cells do not respond to insulin, and central adiposity, or fat accumulation around the midsection.

However, Kanaya was not entirely satisfied. “That didn't seem to really answer the big question for me about why and how do you prevent it,” she said.

To fill this gap, Kanaya launched a longitudinal study called the Mediators of Atherosclerosis in South Asians Living in America (MASALA). The study, whose acronym is a Hindi word for spices, started in 2006 with 150 participants and has now expanded to about 2,300. By examining various health parameters among South Asians, Kanaya and her team pinpointed factors that potentially contribute to heightened diabetes and heart disease risk in this ethnic group. Today, MASALA is the longest-running study tracking South Asian people’s health over time, contributing to a better understanding of not just risk factors but also screening guidelines.

Capturing Differences Among South Asians

For MASALA, Kanaya drew inspiration from the Multi-Ethnic Study of Atherosclerosis (MESA), a longitudinal study examining early atherosclerosis in White, African American, Hispanic, and Chinese populations. Hoping to get a fuller picture of the forces pushing disease in diverse populations, scientists from both studies joined forces.

“Having that MESA comparison really shines a light at how different South Asians are,” said Kanaya. For instance, comparing the body composition among MESA and MASALA participants revealed that the latter had more liver and visceral fat, which are strongly linked with heart disease and diabetes risk.³ They also had lower lean mass, another risk factor for diabetes, compared to other populations.

One of the studies under MASALA also revealed that insulin resistance is not as prevalent as once thought: South Asians are more prone to a less common variant of type 2 diabetes, wherein pancreatic beta cells do not produce enough insulin.⁴ While people who are insulin resistant may respond to certain lifestyle modifications, “those who have [impaired] pancreatic beta cell function are less likely to respond,” said Kanaya, highlighting that there is no one-size-fits-all treatment approach.

Kanaya and her team also argued that since South Asians can develop diabetes at a lower body mass index (BMI) level compared to other populations, the BMI cutoff point for diagnostic tests for them should be lower.⁵ This underscores the importance of having different screening guidelines for this population.

Aside from observing differences between South Asians and others, Kanaya and her team also uncovered an additional layer of variation within the South Asian community. Two centers at Northwestern University and New York University recently recruited Bangladeshi and Pakistani immigrants to the MASALA study. According to Kanaya, Pakistanis have a higher burden of diabetes compared to Indians, and Bangladeshis have an even higher rate of the disease, highlighting the pitfalls of categorizing diverse people under one umbrella population.

Serving the Community at the Heart of MASALA

Kanaya hopes that insights from the MASALA study will aid those she set out to help back in 2006. “It’s important to ground what we do in the communities that we intend to serve,” said Kanaya.

Kanaya and her team educate South Asian people about the novel findings from their studies, “so that what we learn is going back into the communities and hopefully helping raise awareness and prevent disease in those communities.”

Over time, Kanaya hopes to expand the study cohort to obtain even deeper insights into disease risk among South Asians. Until then, she wants to continue doing what they have been doing for the last two decades. “We [want to] continue to raise awareness and learn as much as we can from even this tiny little cohort,” said Kanaya.