TORONTO - 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 has found.
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.
"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.
People in a total of 52 countries were studied.
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 almost 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, says the study published Wednesday in the Journal of the American Medical Association.
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. (1,732 heart attack patients and 2,204 controls from 15 medical centres in the South Asian countries and 10,728 heart attack cases and 12,431 controls from other countries.)
At the same time, South Asians tend to be 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.''
"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.
"We can't change people's genes, but we can change their lifestyles.''
