Elsevier

The Lancet

Volume 356, Issue 9226, 22 July 2000, Pages 279-284
The Lancet

Articles
Differences in risk factors, atherosclerosis, and cardiovascular disease between ethnic groups in Canada: the Study of Health Assessment and Risk in Ethnic groups (SHARE)

https://doi.org/10.1016/S0140-6736(00)02502-2Get rights and content

Summary

Background

Cardiovascular disease rates vary greatly between ethnic groups in Canada. To establish whether this variation can be explained by differences in disease risk factors and subclinical atherosclerosis, we undertook a population-based study of three ethnic groups in Canada: South Asians, Chinese, and Europeans.

Methods

985 participants were recruited from three cities (Hamilton, Toronto, and Edmonton) by stratified random sampling. Clinical cardiovascular disease was defined by history or electrocardiographic findings. Carotid atherosclerosis was measured with B-mode ultrasonography. Conventional (smoking, hypertension, diabetes, raised cholesterol) and novel risk factors (markers of a prothrombotic state) were measured.

Findings

Within each ethnic group and overall, the degree of carotid atherosclerosis was associated with a higher prevalence of cardiovascular disease. South Asians had the highest prevalence of this condition compared with Europeans and Chinese (11%, 5%, and 2%, respectively, p=0·0004). Despite this finding, Europeans had more atherosclerosis (mean of the maximum intimal medial thickness 0·75 [0·16] mm) than South Asians (0·72 [0·15] mm), and Chinese (0·69 [0·16] mm). South Asians had an increased prevalence of glucose intolerance, higher total and LDL cholesterol, higher triglycerides, and lower HDL cholesterol, and much greater abnormalities in novel risk factors including higher concentrations of fibrinogen, homocysteine, lipoprotein (a), and plasminogen activator inhibitor-1.

Interpretation

Although there are differences in conventional and novel risk factors between ethnic groups, this variation and the degree of atherosclerosis only partly explains the higher rates of cardiovascular disease among South Asians compared with Europeans and Chinese. The increased risk of cardiovascular events could be due to factors affecting plaque rupture, the interaction between prothrombotic factors and atherosclerosis, or as yet undiscovered risk factors.

Introduction

Ethnicity-based research can identify new clues to pathogenesis of a disease, since the populations under study are heterogeneous in genetic and lifestyle characteristics. There is increasing evidence that rates of cardiovascular disease vary between ethnic groups. Previous studies indicate that people of South Asian origin have higher rates of this disease than people of European origin, a finding that cannot be explained by differences in conventional cardiovascular risk factors, such as smoking, raised blood pressure, diabetes, or high cholesterol.1, 2 Conversely, people of Chinese origin have lower rates of cardiovascular disease than people of European origin, and with the exception of glucose intolerance, have a more favourable risk factor profile.3, 4

These findings were confirmed by a recent analysis of Canadian mortality data, in which South Asian Canadians had the highest rates of cardiovascular disease, Canadians of European origin had intermediate rates, and Chinese Canadians had the lowest rates.5 To examine this variation we measured the prevalence of cardiovascular disease in Canadians of South Asian, Chinese, and European origin and then identified whether these differences could be explained by: conventional risk factors; novel risk factors (fibrinogen, plasminogen activator inhibitor-1 [PAI-1], lipoprotein (a), homocysteine); or atherosclerosis as measured by B-mode carotid ultrasonography.

Section snippets

Study population

The Study of Health Assessment and Risk in Ethnic groups (SHARE) is a prospective investigation of atherosclerosis, cardiovascular disease, and its determinants in three ethnic groups in Canada: South Asians, Chinese, and Europeans.6 Canadians were classified as South Asian if their ancestors originated from India, Pakistan, Sri Lanka, or Bangladesh; Chinese if their ancestors originated from China, Taiwan, or Hong Kong; and European if their ancestors originated from Europe. Participants were

Ultrasonography

Subclinical atherosclerosis was measured in all participants by carotid B-mode ultrasonography. In Hamilton and Toronto, a high resolution ACUSON/ACOUSTIC RESPONSE TECHNOLOGY ART 1 imaging system (Mountain View, CA, USA), equipped with a 7·5 MHz broad bandwidth frequency carotid probe was used. In Edmonton, the ATL-UM9-HDI (Bothell, WA, USA) imaging system equipped with a 10 MHz transducer was used. All ultrasound examinations were recorded on S-VHS tapes and subsequently digitised and analysed

Participants

Of the 7728 households selected in the initial random sample, 5769 (75%) were contacted, 3172 (55%) of these completed the screening telephone call, and 1566 (49%) were eligible. Of this group, 985 (63%) individuals completed all components of the clinic visit. The response rate among eligible individuals did not vary much between ethnic groups: 342 of 579 (59%) South Asians responded, 317 of 458 (69%) Chinese, and 326 of 529 (62%) Europeans. When data from non-responders (n=1527) were compared

Discussion

We have confirmed the national mortality patterns that Canadians of South Asian origin have an increased prevalence of cardiovascular disease compared with Canadians of European and Chinese origin.5 We reported that carotid atherosclerosis was higher in participants with prevalent disease across all ethnic groups, supporting its validity as a surrogate marker for disease. However, the much lower amount of carotid atherosclerosis seen among South Asians, even after adjustment for age, sex, and

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