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Big data study shows “healthy immigrant effect” in rates of major cardiovascular events in Ontario

August 31, 2015 Toronto

A groundbreaking new study from researchers at the Institute for Clinical Evaluative Sciences (ICES) and the Sunnybrook Schulich Heart Centre demonstrates a “healthy immigrant effect” on heart health in Ontario, with an overall 30 per cent lower rate of major cardiovascular events in Ontario’s recent immigrant population, compared to long-term residents of similar ages. 

CANHEART Study SlideClick for full size image

However, this effect is not uniform: the study also shows that there are striking four-fold variations in the rates of cardiovascular events such as heart attacks and strokes among immigrants to Ontario from different ethnic groups born in various parts of the world. The effect also diminishes in some populations as they spend more time in Canada.

The results of the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) Immigrant study, a “big data” initiative, were published online today in the American Heart Association’s journal Circulation.

Linking information from Citizenship and Immigration Canada’s Permanent Resident database to nine population-based health databases, researchers examined the 10-year incidence of major cardiovascular events (heart attack, stroke, angioplasty, bypass surgery or cardiovascular death) of more than 800,000 first-generation immigrant adults who immigrated to Ontario in 1985 or later. They studied the data to determine patterns and trends across age groups, sex, major ethnic group and over two hundred countries of birth. This information was then compared to a group of over five million long-term Ontario residents, predominantly white, born in Canada.

This study is the most comprehensive and ethnically diverse study of cardiovascular disease in immigrants to Canada to date. It paints a very different picture in Ontario from previous studies, primarily conducted in Europe and the United States, which mostly showed high rates of heart disease in immigrant populations.

“The reasons for the ‘healthy immigrant effect’ in Canada are uncertain,” says Dr. Jack Tu, the study’s lead author and senior scientist at ICES. “Our study suggests that part of it can be explained by most immigrant groups having lower rates of smoking and obesity than Canadian-born individuals. Canada’s medical screening requirement for immigrants also likely plays a role, but other possible reasons require further study.”

Some key findings of the study are:

  • The overall incidence of cardiovascular events was 30 per cent lower in the immigrant population overall, but varied widely across the eight major ethnic groups, with a four-fold difference from best to worst.
  • Most immigrant groups were less likely than long-term Ontarians to smoke and to be obese.
  • East Asian (predominantly ethnic Chinese) immigrants had the lowest incidence of major cardiovascular events overall (2.4 in males and 1.1 in females per 1000 person years). However, after 10 years in Canada, these rates increased by 40 per cent in males and 60 per cent in females.
  • South Asian immigrants (from countries such as India, Pakistan, Bangladesh, Sri Lanka, Guyana) had the highest incidence rates overall (8.9 in males and 3.6 in females per 1000 person years) along with immigrants born in Iraq and Afghanistan.
  • There was a strong association between the overall prevalence of traditional cardiac risk factors (smoking, hypertension, diabetes, high cholesterol) in the different ethnic groups and cardiovascular event rates.

“Canada is one of the most ethnically and culturally diverse high-income countries in the world, but this is the first time it has been possible for us to study the frequency of heart attacks and strokes with this level of detail in our immigrant population,” says Tu, who is also a cardiologist at the Sunnybrook Schulich Heart Centre and Canada Research Chair in Health Services Research at the University of Toronto. “Our study provides new information that shows the importance of creating culturally-tailored prevention strategies and early detection programs so that we can ensure that we are providing the best care for all patients, and the heart health advantages of this healthy immigrant effect do not diminish over time.”

“The incidence of major cardiovascular events in immigrants to Ontario, Canada: the CANHEART immigrant study,” was published today in the journal Circulation.

The study was funded by operating grants from the Institute for Circulatory and Respiratory Health-Canadian Institutes of Health Research and the Heart and Stroke Foundation of Ontario.

Author block:  Jack V. Tu, Anna Chu, Mohammad R. Rezai, Helen Guo, Laura C. Maclagan, Peter C. Austin, Gillian L. Booth, Douglas G. Manuel, Maria Chiu, Dennis T. Ko, Douglas S. Lee, Baiju R. Shah, Linda R. Donovan, Qazi Zain Sohail, David A. Alter.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

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