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The incidence of major
cardiovascular events in
immigrants to Ontario, Canada:
The CANHEART Immigrant Study
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 Z. Sohail,
David A. Alter
Circulation (Online before print August 31, 2015)
Institute for Clinical Evaluative Sciences
Background
• Global migration to high-income countries is increasing.
• Little is known about the incidence of cardiovascular
diseases in migrant populations from different ethnic
backgrounds and regions of the world.
• Previous studies have been primarily been conducted in
Europe. (Dassanayake J, Asia-Pacific Journal of Public Health 2011;23:882-95)
• Among high-income countries, Canada has one of the
highest per-capita rates of immigration.
• Ontario, Canada represents an ideal setting in which to
conduct research on cardiovascular diseases in multi-ethnic
migrant populations.
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Overall Objective
To determine, in a large multi-ethnic cohort of firstgeneration immigrants who immigrated to Ontario
between 1985 and 2000, the:
i.
Prevalence of traditional cardiovascular risk factors
and,
ii. 10-year incidence rates of major cardiovascular
events.
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Methods
• Design
– Retrospective cohort study of 824,662 immigrants from 201 countries of
birth.
– Identified from Citizenship and Immigration Canada’s Permanent Resident
database, linked to 9 population-based health databases.
• Inclusion/Exclusion Criteria
– All legal immigrants aged 30-74 years as of January 2002, who landed in
Ontario between 1985 and 2000.
– No known history of a major cardiovascular event prior to January 2002.
• Immigrants classified into 1 of 8 major ethnic groups, based upon their country
of birth, mother tongue and surname. (Rezai M, Open Med 2013; 7:85-93; Shah B, BMC Medical
Research Methodology 2010;10:42)
–
White-Western European (including US, Australia, New Zealand), White-Eastern
European, East Asian, Black, Southeast Asian, Latin American, West Asian/Arab (Middle
East), South Asian.
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Data Sources
Socio-demographics:
Citizenship and Immigration
Canada (CIC) Permanent Resident
Database
Ontario Registered Persons
Database
Ontario Drug Benefits Claims
Database
Health care utilization:
Ontario Health Insurance Plan
Physician Claims Database
CIHI Hospital Discharge Abstract
Database*
Ontario Visible Minority Database
CVD risk factors:
Canadian Community Health
Survey (smoking, BMI)
Ontario Hypertension Database
Ontario Diabetes Database
Gamma-Dynacare Medical
Laboratories (lipids)
Clinical outcomes:
STUDY COHORT
CIHI Hospital Discharge Abstract
Database*
• 824,662 immigrants
Registrar General of Ontario Vital
Statistics Database
• 5,200,258 long-term
residents†
• 30-74 years of age
on January 1, 2002
* CIHI=Canadian Institute for Health Information
† Born in Canada or immigrated prior to 1985.
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Primary Outcome
Age-standardized 10-year incidence rate of a major
cardiovascular event (2002-2011)
Defined as a composite outcome consisting of:
• Acute myocardial infarction (AMI) – “Heart Attack”
• Stroke
• Percutaneous coronary intervention (PCI)
• Coronary artery bypass graft surgery (CABG)
• Cardiovascular (CVD) death
(All results standardized to the 2006 Ontario census population)
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Cardiac Risk Factor Score
• Purpose: To quantify the relative combined burden of
four traditional modifiable cardiac risk factors —
smoking, diabetes, hypertension and hyperlipidemia.
• A points-based score using similar methods to those
used in creating the Framingham risk score. (Sullivan LM,
Statist Med 2004;23:1631-60)
• Points for each risk factor are determined from βcoefficients from a multivariate Cox proportional hazards
model.
• Higher scores = higher risk
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Cardiac Risk Factor Score Points System
Risk Factor
Age (years)
Category
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
Males’ Points
-2
-1
0
1
2
3
4
5
Females’ Points
-2
-1
0
1
2
3
4
5
70-74
6
6
1
2
1
2
< 4.14
-1
0
4.14 – 5.15
5.16 – 6.19
6.20 – 7.22
≥ 7.23
< 1.03
1.03 – 1.28
0
0
1
2
1
0
0
0
1
1
1
0
1.29 – 1.53
-1
0
≥ 1.54
-1
2
-4 to 14
-1
2
-3 to 13
Hypertension
Diabetes
Total cholesterol (mmol/L)
HDL cholesterol (mmol/L)
Smoker
Total points range (minimum – maximum)
* Categories in bold are the reference categories.
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Statistical Analyses
• Age-standardized 10-year incidence rates per 1000 personyears follow-up were calculated using the 2006 Ontario
population aged 30 to 74 as the standard population.
• Sex-stratified analyses by country of birth for those 29
countries with at least 5000 immigrants to Ontario.
• Pearson correlation coefficients to examine the association
between the mean ethnic-group specific cardiac risk factor
score and the ethnic-group specific incidence rate of
cardiovascular events.
• Sex-stratified, sequential Cox proportional hazard modelling
to investigate differences in the primary outcome between
ethnic groups and the long-term resident cohort.
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Study cohort includes immigrants from
201 countries of birth from around the world
1985-2000
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Baseline Characteristics of Immigrants
(in order of CVD risk among males)
Black
WhiteWestern
European
Southeast
Asian
Latin
American
West
Asian/
Arab
WhiteEastern
European
South
Asian
All
Immigrants
174,167
84,914
82,998
68,239
55,173
71,770
121,912
165,489
824,662
Age on arrival,
years*
38
33
33
36
34
35
35
37
36
Age on Jan 1,
2002, years*
45
42
44
44
44
43
44
44
44
Females, %*
52
51
50
60
49
42
50
47
50
Completed
university, %
26
8
19
28
12
32
31
28
24
58
34
3
30
52
18
57
42
0
43
47
10
30
46
23
43
27
29
34
29
37
39
47
12
43
40
15
8.1
9.5
10.5
8.9
9.9
8.1
8.5
7.6
8.6
44
50
6
20
46
34
93
7
0
0
80
20
0
100
0
6
84
11
1
99
0
3
29
68
22
57
21
Variable/
Ethnic
Group
East
Asian
Population size,
n
Immigration
class, %
Economic†
Family
Refugee
Years in Ontario
(to Jan 1, 2002)
Country of birth
income group
High
Middle
Low
* Unadjusted results. All other results are age-/sex-standardized.
† Includes skilled workers, entrepreneurs, self-employed, live-in caregivers, investors and their dependents.
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Risk factors – Immigrants vs Long-term
Residents*
Risk Factors at Baseline
(January 1, 2002)
Males
Females
All Immigrants
Long-term
Residents
All Immigrants
Long-term
Residents
412,875
2,484,554
411,787
2,715,704
Current cigarette smoker, %
24.5
28.7
8.6
23.8
Hypertension, %
17.9
20.6
20.3
21.3
Diabetes, %
8.8
7.3
8.2
6.0
5.3
5.3
5.2
5.4
1.3
1.3
1.5
1.6
4.4
4.4
3.6
3.6
Body mass index, kg/m2
25.6
27.2
24.7
26.0
Cardiac risk factor score
2.2
2.3
1.8
2.1
Population size, n
Mean total cholesterol,
mmol/L
Mean HDL cholesterol,
mmol/L
Mean total to HDL cholesterol
ratio
*All results are age-standardized.
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Age-standardized prevalence of cardiovascular risk factors by
ethnicity
▪
East Asian
▪
Males
Females
East Asian
Black
Black
White-Western European
White-Western European
Southeast Asian
Southeast Asian
Latin American
Latin American
West Asian/Arab
West Asian/Arab
White-Eastern European
White-Eastern European
South Asian
South Asian
Long-term Residents
Long-term Residents
0
10
20
30
40
Smoking Prevalence, %
50
0
East Asian
East Asian
Black
Black
White-Western European
White-Western European
Southeast Asian
Southeast Asian
Latin American
Latin American
West Asian/Arab
West Asian/Arab
White-Eastern European
White-Eastern European
South Asian
South Asian
Long-term Residents
Long-term Residents
0
5
10
15
20
25
Diabetes Prevalence, %
30
35
2.5
5
10
15
20
25
30
Hypertension Prevalence, %
35
3.0
3.5
4.0
4.5
Mean Total/HDL Cholesterol Ratio
5.0
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Age-standardized incidence of a major cardiovascular event by
ethnicity, 2002-2011*
Males
East Asian
Black
White-Western European
Southeast Asian
Latin American
West Asian/Arab
White-Eastern European
South Asian
All
Allimmigrants
Immigrants
Long-term
Long-termResidents
residents
2.4
4.7
4.8
5.4
5.6
6.7
7.2
8.9
5.6
8.1
Females
East Asian
White-Western European
Southeast Asian
White-Eastern European
Black
Latin American
West Asian/Arab
South Asian
Allimmigrants
Immigrants
All
Long-termResidents
residents
Long-term
1.1
2.1
2.1
2.5
2.7
2.9
2.9
3.6
2.4
3.4
0.0
2.0
4.0
6.0
8.0
Incidence rate, per 1000 person-yrs
10.0
*A major cardiovascular event includes AMI, stroke, PCI, CABG surgery or death due to IHD or stroke.
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Incidence of a Major Cardiovascular Event
by Duration of Residence - Males*
12
Incidence rate, per 1000 person-years
In Ontario <10 yrs
10
In Ontario 10+ yrs
8
↑10%
6
4
↑40%
2
0
*AMI, stroke, PCI, CABG surgery or death due to IHD or stroke. All results are age-standardized.
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Incidence of a Major Cardiovascular Event
by Duration of Residence - Females*
5
Incidence rate, per 1000 person-years
In Ontario <10 yrs
In Ontario 10+ yrs
4
3
↑10%
2
↑60%
1
0
*AMI, stroke, PCI, CABG surgery or death due to IHD or stroke. All results are age-standardized.
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Age-standardized incidence of a major cardiovascular event by
country and region of birth among 29 countries of birth with at
least 5000 immigrants, 2002-2011*
Males
Females
Taiwan
Hong Kong
China
South Korea
Taiwan
Hong Kong
China
South Korea
United States
Portugal
United Kingdom
United States
Portugal
United Kingdom
Ghana
Somalia
Ethiopia
Jamaica
Trinidad & Tobago
Ethiopia
Somalia
Ghana
Jamaica
Trinidad & Tobago
Southeast Asia
Vietnam
Philippines
Vietnam
Philippines
Latin America
El Salvador
Guyana
El Salvador
Guyana
Iran
Lebanon
Egypt
Afghanistan
Iraq
Lebanon
Iran
Egypt
Iraq
Afghanistan
Romania
Yugoslavia
Russia
Poland
Romania
Yugoslavia
Russia
Poland
India
Bangladesh
Pakistan
Sri Lanka
Sri Lanka
India
Pakistan
Bangladesh
Long-term Residents
Residents
Long-term
Long-term Residents
Residents
Long-term
East Asia
Western Europe/
United States
Sub-Saharan Africa/
Caribbean
Middle East/West Asia
Eastern Europe
South Asia
0
2
4
6
8
10
12
0
Incidence, per 1000 person-years (95% CI)
2
4
6
8
10
12
Incidence, per 1000 person-years (95% CI)
*A major cardiovascular event includes AMI, stroke, PCI, CABG surgery or death due to IHD or stroke.
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Age-standardized cardiac risk factor score versus incidence of a major
cardiovascular event by ethnicity and country of birth, 2002-2011*
Females
By ethnicity, R=0.76
10
9
South Asian
Long-term resident
8
White-Eastern European
7
6
West Asian
Latin American
Southeast Asian
Black
White-Western European
5
4
3
East Asian
2
1
Incidence of a major cardiovascular event,
per 1000person-years
Incidence of a major cardiovascular event,
per 1000person-years
Males
By ethnicity, R=0.92
4
South Asian
Long-term resident
3
Latin American
Black
Southeast Asian
White-Eastern European
2
East Asian
1
0
0
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
1.0
1.2
1.4
Mean cardiac risk factor score
Incidence of a major cardiovascular event,
per 1000 person-years
Sri Lanka
Iraq
Afghanistan
Pakistan
Bangladesh
Russia India
Poland
Trinidad & Tobago
Egypt
Yugoslavia
Lebanon
Romania
Iran
United Kingdom
Philippines
Portugal
El Salvador
Jamaica
Vietnam
United StatesSomalia Ethiopia
South Korea
Ghana
China
Hong Kong
Taiwan
8
6
4
2
1.8
2.0
2.2
By country of birth, R=0.75
7
Guyana
10
1.6
Mean cardiac risk factor score
By country of birth, R=0.81
12
Incidence of a major cardiovascular event,
per 1000 person-years
West Asian
White-Western European
Afghanistan
6
5
Iraq
Guyana
Bangladesh
Trinidad & Tobago
Pakistan
India
Sri Lanka
4
3
Jamaica
Poland
United Kingdom Russia Yugoslavia Egypt
Iran Portugal
Romania
South Korea
Vietnam Philippines El Salvador
Lebanon
United States
Ethiopia
Ghana
Somalia
Hong Kong
China
Taiwan
2
1
0
0
1.0
1.5
2.0
2.5
3.0
1.0
1.2
1.4
Mean cardiac risk factor score
1.6
1.8
2.0
2.2
2.4
Mean cardiac risk factor score
*A major cardiovascular event includes AMI, stroke, PCI, CABG surgery or death due to IHD or stroke.
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Adjusted relative risk of a major cardiovascular event by
ethnicity compared with long-term residents, 2002-2011*
Hazard Ratio (95% CI)
Long-term residents (ref)
Males
East Asian
Black
White-Western European
Southeast Asian
Latin American
West Asian/Arab
White-Eastern European
South Asian
0.32 (0.30, 0.34)
0.59 (0.55, 0.64)
0.61 (0.57, 0.64)
0.62 (0.57, 0.68)
0.63 (0.58, 0.67)
0.75 (0.71, 0.80)
0.83 (0.79, 0.87)
1.02 (0.99, 1.06)
Females
East Asian
Southeast Asian
White-Western European
Latin American
White-Eastern European
Black
West Asian/Arab
South Asian
0.38 (0.35, 0.41)
0.56 (0.51, 0.61)
0.68 (0.62, 0.75)
0.71 (0.65, 0.79)
0.73 (0.68, 0.78)
0.73 (0.67, 0.79)
0.76 (0.69, 0.85)
0.89 (0.85, 0.93)
0.25
0.50
1.00
Hazard Ratio (95% CI)
1.50
*Adjusted for age, income quintile, smoking, diabetes, hypertension, total cholesterol and HDL cholesterol.
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Summary
• The 10-year incidence of major cardiovascular events is 30% lower in male
and female immigrants as compared with long-term residents of Ontario.
• Striking 4-fold variation in event rates between immigrants from different
ethnic backgrounds.
• Lower rates of smoking and obesity in most immigrant groups likely
contribute to the ‘healthy immigrant’ effect.
• East Asian immigrants have the lowest CVD event rates, but the rates
increase dramatically with longer duration of residence in Canada.
• Immigrants of South Asian origin and those born in Iraq and Afghanistan
have the highest risk of cardiovascular events.
• Variations in CVD event rates can be explained in part by variations in the
burden of traditional cardiovascular risk factors but other factors (e.g.
lifestyle, environment, genetics, etc.) also likely play an important role.
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Funding Sources
This study was supported by operating grants from:
• Public Health Agency of Canada
• Institute for Circulatory and Respiratory Health-Canadian
Institutes of Health Research (ICRH-CIHR) Team GrantChronic Disease Risk and Intervention Strategies (#TCA
118349)
• CIHR operating grant (#MOP-111035)
• Heart and Stroke Foundation of Ontario (pilot grant)
The opinions, results and conclusions reported in this paper are
those of the authors and independent from the funding sources.
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