TORONTO - The longer immigrants reside in Canada, the greater their risk of developing cardiovascular disease -- and that effect is most pronounced among people of Chinese origin, a study suggests.
Doctors have long known that the longer people stay after immigrating to western countries like Canada, the less healthy they become, said principal investigator Maria Chiu, a doctoral fellow at the Institute for Clinical Evaluative Sciences.
"What we did not know was whether the degree to which this change happened was different for ethnic groups that lived in Canada."
Using population and health data, Chiu and her co-authors looked at the prevalence of risk factors for heart disease and stroke among immigrants who had lived in Ontario for 15 years or longer, compared to those who had resided in the province for less than 15 years.
They found that longer-term residents exhibited increased risk factors for cardiovascular disease -- among them Type 2 diabetes, obesity, smoking and high blood pressure -- compared with more recent ethnically matched immigrants.
"And it didn't matter whether you were white, Chinese, South Asian or black, this trend was seen across all the major ethnic groups living in Canada," Chiu said Monday. "We also noticed that the degree to which cardiovascular health declined was different across different ethnic groups."
Canadians of Chinese descent showed the worst decline in heart health over time, she said, followed by whites, blacks and South Asians.
Diabetes appears to be the primary reason: the disease was almost twice as common among long-term residents of Chinese and Caucasian descent than among more recent immigrants of the same ethnic backgrounds.
"This is likely driven by higher rates of obesity in these groups," said Chiu, noting that those living in Canada for 15 years or more had a 30 to 40 per cent higher obesity rate compared to their shorter-stay counterparts.
"Chinese are gaining more weight and developing more diabetes the longer they live here, more than any other ethnic group," she said. "It's no secret that the western diet is not the healthiest, and it's been found that the longer people stay in the western culture, the more likely they are to pick up bad habits, such as eating more frequently at fast-food restaurants, eating food high in fat and added sugars, and eating between meals.
"These bad habits are likely picked up by all the ethnic groups, but our study suggests that the Chinese and white groups are likely to adopt these bad habits to a greater degree than the other groups."
The study, published Tuesday in the Canadian Journal of Cardiology, also found smoking was a prominent risk factor for blacks and South Asians who had been in Canada 15 years or more -- and the difference was most evident among females.
"So South Asian and black females who were born in Canada or lived in Canada for at least 15 years were three to four times more likely to smoke than their recent immigrant counterparts," said Chiu, calling it a surprising finding since Ontario and the rest of the country have strict anti-smoking laws.
"We would have expected a decrease. But obviously there is vulnerability in the female population of people of South Asian and black descent that we really need to target our anti-smoking messages to, a little more effectively."
Higher psychosocial stress was also found among South Asian females who had been in the country at least 15 years, and although the researchers don't know the reasons behind it, stress rates correlated with increased tobacco use within this group.
While having a different genetic makeup can explain in part why some ethnicities are more prone to certain diseases, environment is also known to play a role. The question for researchers has long been which is it: one or the other or a combination of both?
"What makes this study interesting is that we compared similar genetic makeup, meaning Chinese versus Chinese who lived here longer versus those who were recent immigrants and we looked at how they differed," Chiu said. "So you're looking at people with similar genetic makeup and the only thing that's different between them is how long they've stayed here in a western culture.
"So this study further emphasizes that we can't blame all the risks of cardiovascular disease on genetics. We can't use that excuse that, 'Oh, we have bad genes, we can't help but get heart disease."'
She said the findings suggest that better strategies are needed to educate immigrants about trying to avoid adopting unhealthy dietary and other lifestyle habits in their new country that put them at an elevated risk of potentially deadly heart disease and stroke.
"Prevention is better than cure ... we need to protect the health of new immigrants from the get-go."
Some organizations, including the Heart and Stroke Foundation, have launched initiatives aimed specifically at ethnic populations.
"Having a better understanding of how length of time living in Canada impacts cardiovascular risk factors will help us to develop tailored prevention strategies to ensure the long-term heart health of all Canadians," said Vincent Bowman, director of research for the foundation's Ontario division.
Such programs are critical now -- more than 250,000 immigrants settle in Canada each year -- and for the country's future, said Chiu.
"Immigrants represent a large and growing segment of our Canadian population and we know that by 2031, immigrants are going to be responsible for the net growth of the Canadian population. So there's a need to better understand how we can preserve the healthy lifestyles of people who recently immigrate to Canada and how we can reduce the negative influences for the future."
