The study was primarily funded by the Heart and Stroke Foundation of Ontario (HSFO).
“We have found that the definition we’re currently using for obesity (BMI of 30+), which was developed and used mainly in white populations, provides a false sense of security for nonwhite ethnic groups. This is because risk of diabetes is so much higher at much lower levels of BMI than the white group,” says Maria Chiu, principal investigator of the study and ICES Doctoral Fellow. “For the equivalent incidence rate of diabetes at BMI 30 in the white group, the BMI threshold was 24 in the South Asian group, 25 in the Chinese group, and 26 in the black group,” says Chiu who is also a University of Toronto PhD Candidate and Canada Graduate Scholar of the Canadian Institutes of Health Research (CIHR).
Type 2 diabetes is a growing epidemic in Canada and globally. People of South Asian, Chinese and black ethnic background represent approximately 60 per cent of the world’s population, but little is known about how these ethnic groups differ in their incident rates of diabetes and whether diabetes occurs at younger ages in some ethnic groups. There are nearly two million people of South Asian, Chinese or black descent and more than 9 million people of European descent living in Ontario. An ethnically-tailored approach to screening and prevention might be more effective in reducing diabetes in a multi-ethnic Canadian population. Specifically, the study highlights that the definition of obesity (BMI of 30+) widely used in White populations, may not be appropriate in nonwhite populations.
“This is a timely study, not just for diabetes, but for cardiovascular disease as well. It will help inform the work the Foundation has been undertaking to better understand the potential interventions, programs and policies that could be used to address multicultural differences in cardiovascular disease and related risk factors, including diabetes,” says Manuel Arango, Director of Government Relations, Heart and Stroke Foundation of Canada.
The study quantified the development of diabetes in 59,824 Ontarians aged 30 years and over who were initially free of the disease. The study found:
- The rate of new cases of diabetes was highest among South Asian subjects, followed by black, Chinese and white subjects.
- Specifically, as compared to white persons, incidence rate of diabetes was 3.4-fold higher among South Asian, 2-fold higher among black and 1.9-fold higher among Chinese persons; this was after adjusting for age, sex, income, urban/rural dwelling, and BMI.
- The median age at diagnosis was lowest among South Asian subjects (49 years), followed by Chinese (55 year), black (57 years), and white (58 years) subjects.
- On average, diagnosis of diabetes occurred 9 years earlier among South Asian, 3 years earlier among Chinese and 1 year earlier among black subjects than among white subjects.
- For the equivalent incidence rate of diabetes at BMI 30 in white persons, the BMI threshold value was 24 in South Asian, 25 in Chinese, and 26 in black persons.
“The findings have very important implications for the future of diabetes care in Canada, as the proportion of Canada’s population in visible minority groups increases over time. Health promotion experts, health system planners, and the general population need to be aware of these findings, so that they can target their diabetes risk prevention and treatment efforts most effectively,” says Jack Tu, senior author of the study, Senior Scientist at ICES, HSFO Career Investigator and staff cardiologist, Schulich Heart Centre, Sunnybrook Health Sciences Centre.
Author block: Maria Chiu, Peter C. Austin, Douglas G. Manuel, Baiju R. Shah, and Jack V. Tu.
The study “Deriving Ethnic-Specific Body-Mass Index Cutoff Points for Assessing Diabetes Risk” is available online on June 16, 2011 and will be in the August issue of Diabetes Care.
More detailed study findings on the ICES website: www.ices.on.ca
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.
The Heart and Stroke Foundation, a volunteer-based health charity, leads in eliminating heart disease and stroke and reducing their impact through the advancement of research and its application, the promotion of healthy living and advocacy.
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