South Asians at greater risk for heart attack, even after immigrating: study

Provided by: Canadian Press
Written by: SHERYL UBELACKER
Jan. 16, 2007

TORONTO (CP) - South Asians have heart attacks at a younger age compared to other ethnic groups because of higher risk factors for cardiovascular disease - and the danger can persist even if they immigrate to Canada or another western country, a landmark study suggests.

The research, part of a massive Canadian-led international study on cardiovascular disease, found that deaths from heart attack occur among people native to India, Pakistan, Bangladesh, Nepal and Sri Lanka five to 10 years earlier than among those from other populations.

"South Asian people who represent approximately 1.5 billion people in the world, which is in fact a quarter of humanity, seem to have a special predilection for getting heart disease," said principal investigator Dr. Salim Yusuf of McMaster University.

"What this really means is we need to be very aggressive about promoting the right lifestyle in South Asians, and that should make a big impact," he said, noting that about 1.2 million people of South Asian descent live in Canada.

The research, published Wednesday in the Journal of the American Medical Association, is part of the much larger INTERHEART study, which included analysis of 30,000 participants from 52 countries. (This study involved roughly 1,700 heart attack patients and 2,200 controls from the five South Asian countries and about 10,700 heart attack cases and 12,500 controls from other countries.)

"We did this study to find out why do South Asians get more heart disease," Yusuf said Tuesday from Hamilton, noting that previous research has suggested that South Asians must have some unusual risk factors because of their propensity for heart problems at any earlier age.

No genetic predisposition has been identified that would increase South Asians' susceptibility to cardiovascular disease, although researchers worldwide are investigating genetic risk factors for various chronic diseases among different populations.

Yusuf and his fellow researchers - including a team led by Dr. Prashant Joshi of the Government Medical College in Nagpur, India - found that the average age for first heart attack was 53 in the five South Asian countries, compared with age 59 in other countries.

"And much to our surprise, we found that you could actually explain this excess in heart disease when you tabulate the data by age," said Yusuf, director of McMaster's Population Health Research Institute.

It turns out that the same nine risk factors for cardiovascular disease at play in populations from Australia to Zimbabwe are at play among South Asians - they are just more pronounced.

Leisure-time physical activity, daily consumption of fresh fruit and vegetables, and daily but moderate alcohol intake were markedly lower among South Asian study participants compared with those from other countries.

At the same time, South Asians tend to have a greater prevalence of diabetes, high blood pressure, abdominal obesity, psychosocial factors such as depression and stress at work or home, and artery-clogging blood fats (lipids). Tobacco smoking is also a factor.

While South Asian women are far less likely to smoke than the men, their risk for early death from heart attack is similar because of higher obesity and diabetes rates among females, the study found.

And moving to Canada or another western country doesn't necessarily alter those risks, either for immigrants themselves or their western-born offspring. In fact, other researchers have shown that "children of South Asians living in the U.K. have higher risk factors than the native Brits," Yusuf said. "Even at the age of six or seven, there are higher risk factors."

Ottawa cardiologist Dr. Andy Wielgosz said immigrants from South Asian countries may continue unhealthy, culturally ingrained behaviours in Canada - and those may get passed to their children.

"One's own home is a major influence in the kind of lifestyle that you develop," said Wielgosz, who is also a spokesman for the Heart and Stroke Foundation. "If their parents are smokers or physically inactive or eating a high-fat diet, then young Canadians of South Asian origin are already at increased risk for developing those same kinds of habits and being at increased risk."

Dr. Robert Hegele, an endocrinologist who specializes in cardiovascular disease, said the study confirms with hard data - by counting actual heart attacks - doctors' long-held suspicions that South Asian patients indeed have a higher risk profile than many other ethnic groups.

"The reasons for these differences are probably complex and it probably is a combination of lifestyle environmental factors and probably genetic as well, although actual genetic markers have not been yet discovered that would explain those differences," Hegele, director of the Blackburn Cardiovascular Genetics Lab at the Robarts Research Institute, said from London, Ont.

"What this study really shows is the good news, that these are largely modifiable risk factors and even if there is a genetic component, we know that in fact a lot of these things can be improved with lifestyle interventions."

While Wielgosz said that getting people to change is a challenge - he himself comes from an eastern European background with a culture of fatty diets - modifying behaviour can make a huge difference in preventing cardiovascular disease.

"This is where research is focusing now - how to motivate change . . . We certainly know you have to find the appropriate means of communication. A simple example is language: you need to be able to speak the language of those who are newly arrived immigrants and you need to phrase your recommendations in culturally relevant terms."

"But it can be done," he said. "And it doesn't have to take as long as another generation."