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The formulas doctors use to determine a person's risk for heart disease – which guides prevention and treatment plans – may not accurately reflect the higher risk faced by people of South Asian descent, according to new research.

About a quarter of the world's population, about 1.8 billion people, are of South Asian descent, and they are twice as likely to have heart problems as people with European ancestry.

Yet, the study, published Monday in the ľ¹ÏÖ±²¥ journal , found the standard risk calculators used in the United States and Europe to predict the likelihood of having a heart attack or stroke failed to accurately predict the higher risk in people who were born in or descended from India, Pakistan, Bangladesh, Bhutan, Maldives, Nepal or Sri Lanka compared to those with white British, white Irish or other white European backgrounds.

"We were surprised by the magnitude of the increased risk – even within contemporary clinical practice, it was more than double – and how much of it remains unexplained by traditional clinical or lifestyle risk factors," senior study author Dr. Amit V. Khera said in a news release. Khera is a cardiologist in the Corrigan Minehan Heart Center and leads a research group at Massachusetts General Hospital's Center for Genomic Medicine in Boston.

Current risk assessment tools fail to predict the extra risk, he said, "likely because no South Asians were included in developing the U.S. tool, so we may be missing opportunities to prevent heart attacks and strokes in this group. Intensive control of risk factors like high cholesterol and Type 2 diabetes are even more important in this population."

Researchers analyzed medical data in the U.K. for 8,124 people of South Asian ancestry and 449,349 people of European ancestry, comparing their rates of developing cardiovascular disease. Over an average of 11 years, 6.8% of people with South Asian heritage had a heart attack or stroke or required a procedure to restore normal blood flow to the heart, compared to 4.4% of people with European ancestry.

People in the South Asian study group were more likely to have risk factors for heart disease, including Type 2 diabetes, high blood pressure and increased central adiposity, or belly fat. But even after accounting for these risks, people of South Asian ancestry still faced a 45% higher risk for heart trouble.

"We need to dig deeper to better understand why South Asians are having heart attacks and strokes at higher rates even after accounting for these risk factors," lead study author Dr. Aniruddh Patel said in the news release.

"Our ability to study South Asian and other populations in general in the United States using public databases has been limited because individuals are grouped together by race rather than ancestry," said Patel, a cardiology fellow at Massachusetts General Hospital.

That's made recognizing and addressing health disparities among a fast-growing South Asian population in the U.S. more difficult, he said.

"In addition to recruiting more South Asians in clinical trials and cohort studies," Patel said, "better reporting of ancestry, in addition to race in hospital data systems and electronic medical records, would help us better understand and target these disparities."

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