Chapter 1
Risk Factors
As the Victoria Declaration on Heart Health aptly stated:
Cardiovascular disease is largely preventable. We have the scientific knowledge to create a world in which most heart disease and stroke could be eliminated.
(Advisory Board of the International Heart Health Conference 1992)
Even though the scientific knowledge exists, preventing heart disease and stroke is a complex undertaking. Their prevention requires action at multiple levels. Primary prevention aims to reduce the incidence of disease by controlling risk factors. Secondary prevention attempts to reduce the prevalence of disease by early diagnosis and treatment. The goal of tertiary prevention is to limit the progress or complications of established disease.
Mortality from ischemic heart disease in North America has declined steadily since the 1960s. It is estimated that 25% of the decline in the United States between 1980 and 1990 was due to efforts in primary prevention, 29% to secondary prevention, and 43% to improvements in treatment.
A growing body of evidence suggests that the determinants of health go beyond individual genetic endowment, lifestyle behaviour and the health care system to include more pervasive forces in the physical, social and economic environment. Thus, a fourth and even earlier stage, primordial prevention, has been proposed. Primordial prevention aims at avoiding the emergence of the social, economic and cultural patterns of living that are known to contribute to an elevated risk of disease. Health policy-makers and analysts have emphasized the need to address these underlying determinants in order to prevent heart disease and stroke. They urge us to direct attention toward modifying not only risk factors and risk behaviours, but also such “risk conditions” as poverty, powerlessness and lack of social support. Chapter 5 will discuss these determinants in more detail.
Risk Conditions
Age
Increased age is the dominant risk condition for heart disease and stroke. Rates of all major forms of heart disease increase with advancing age. As the Canadian population ages, the number of individuals with heart disease and stroke is expected to increase.
Sex
At younger ages, men are at much higher risk than women of developing coronary artery disease (CAD). Men tend to have a ten year lead on women in the development of CAD. They are also at higher risk of stroke. (See Chapter 4 "Health Outcomes" for differences among men and women in mortality rates for heart disease and stroke.)
Family History
A family history of early coronary disease is an important risk factor for CAD. It is also an independent risk factor for stroke. The factors that contribute to this association may include familial factors, lifestyle and molecular defects in vascular physiology, which render the vessel wall more susceptible to atherosclerosis. Promising research findings will likely result in genetic typing and gene-specific treatment to prevent heart disease. The extent to which the findings will be of benefit to the general population is as yet unclear.
Modifiable Risk Factors
Modifiable risk factors are those over which an individual has some control, and that he or she can modify in order to reduce their risk of developing heart disease or stroke. Table 1-1 lists the major modifiable risk factors for heart disease and stroke.
While this report discusses each risk factor individually, in reality many people have more than one risk factor. In 2000, the Canadian Community Health Survey (CCHS) found that 80.2% of the population between the ages of 20 and 59 years had at least one of the following risk factors: daily smoking, physical inactivity, being overweight, high blood pressure or diabetes (Table 1-2). The survey also included a question about consumption of fresh fruits and vegetables. Although this is not a major independent risk factor, adding the prevalence of consumption of fresh fruits and vegetables below the recommended daily amounts would increase the prevalence of one or more combined risk factors in the Canadian population to 90%. The risk of heart disease and stroke increases with an increased number of risk factors.
A recent study by the World Health Organization (WHO) has identified tobacco use, high blood pressure, alcohol consumption, high cholesterol, high body mass index (BMI), low consumption of fruits and vegetables, and physical inactivity as the top seven contributors to the burden of disease in developed countries. Blood glucose was not included in this study.
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Table 1-1 Modifiable Risk Factors (self-reported) among Adults Aged 20-59, Canada, 2000 |
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|
Risk Factor |
Proportion of
the Population (%) |
|
Tobacco Smoking (Daily) |
25.7 |
|
Physical Inactivity |
55.5 |
|
Overweight (BMI > 25.0) |
47.5 |
|
Less than Recommended Consumption of Fruits and Vegetables |
64.7 |
|
High Blood Pressure |
8.3 |
|
Diabetes* |
2.7 |
|
* For the purposes of this report diabetes is listed as a major risk factor. Source: Statistics Canada, Canadian Community Health Survey |
|
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Table 1-2 Combined Risk Factors for Cardiovascular Disease (self-reported) among Adults Aged 20-59 Years, Canada, 2000 |
|
|
Number of Risk Factors |
Risk Factors (% of population) |
|
No Risk Factors |
19.8 |
|
At Least 1 Risk Factor: |
80.2 |
|
1 Risk Factor |
39.1 |
|
2 Risk Factors |
30.0 |
|
3 or More Risk Factors |
11.1 |
|
Source: Statistics Canada, Canadian Community Health Survey |
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Tobacco Smoking
Tobacco use is the major cause of preventable death in Canada. Smoking is responsible for approximately the equivalent number of deaths due to cardiovascular diseases and cancer. Smoking increases the risk of developing all major forms of cardiovascular diseases. In addition, women who smoke and use oral contraceptives have an increased risk of subarachnoid hemorrhage.
The data in this section include individuals aged 15+ years, the entire sample in the Canadian Tobacco Use Monitory Survey (CTUMS).
According to CTUMS, 21.7% of the population aged 15+ years were current smokers. Of these, 18.1% were daily smokers and 3.7% were occasional smokers. The percentage of daily smokers decreased from 21% in 1999 and this was evident among both men and women (Figure 1-1).
Sixteen percent of teenage men (15-19 years) smoked daily in 2001, a decrease from 19% in 1999. Among teenage women the prevalence was 17%, down from 21% in 1999.
In 2001, the percentage of men who were daily smokers increased during the teenage years, and then remained the same until reaching the 50-59 year old age group, at which point the percentage of daily smokers decreased with age (Figure 1-2). The pattern among women differed, however, in that the percentage of daily smokers continued to increase in their 20s, then showed a large decrease in their 30s. The reasons for this, though unclear, may reflect a decrease in smoking while childbearing. The percentage then increased to a level similar to that of women in the late teens. After the age of 50 years, the percentage decreased in the same manner as among men.
The percentage of adults who smoked daily in 2001 was lower in B.C. and Ontario than in all other provinces (Figure 1-3).
Among women, the highest percentage of daily smokers in 2001 was in the lowest income category (Figure 1-4). Among men, the highest percentage was in the low and medium low income categories.
Note: For definition of Income Adequacy, see Glossary.
According to CTUMS, a lower percentage of men who had some post-secondary education or who had completed post-secondary education smoked daily in 2001 (Figure 1-5). Among women, the lowest percentage of daily smokers was among those with a post-secondary degree or diploma.
Physical Inactivity
Physical inactivity is a risk factor for cardiovascular diseases (See Glossary for definition of Physical Inactivity). Regular physical activity can reduce body weight, improve serum lipids and cholesterol, blood pressure and diabetes, and thereby reduce overall cardiovascular risk. National guidelines recommend the development of an active lifestyle that includes 60 minutes of light physical activity or 30 minutes of moderate physical activity each day.
Only data from the CCHS include individuals aged 12+ years.
In 2000, over one-half (56.5%) of adults were physically inactive in their leisure time (Figure 1-6). More women than men were physically inactive. From 1994 to 2000, levels of physical inactivity among adults dropped from 61.6% to 56.5%. This improvement occurred among both men and women.
In general, physical inactivity increased with age in 2000 (Figure 1-7). The exception appeared among men aged between 60 and 69 years who showed less inactivity compared to the 50-59 year age group. More women then men were physically inactive in all age groups. Young women between 12 and 19 years of age were 1.5 times more likely than their male counterparts to be physically inactive. The percentage of men who were physically inactive increased dramatically between the 12-19 and 20-29 year age groups.
In 2000, the percentage of the general population that was physically inactive varied by province/territory (Figure 1-8). The lowest percentages of inactivity were in the Yukon, B.C. and Alberta. The percentages of people who were physically inactive were higher in Newfoundland, P.E.I., New Brunswick, Quebec and Manitoba than in the Canadian population as a whole.
In 2000, men and women in the lowest income category were 1.3 times more likely to be physically inactive than those in the highest income category (Figure 1-9). There was no significant difference in physical inactivity between the two lower income levels.
The percentage of men who were physically inactive was lowest among those with some post-secondary education (Figure 1-10). Among women, those with some post-secondary education or a post-secondary degree were less likely to be physically inactive than those with secondary education or less.
Figure 1 - 10
Overweight
Being overweight - either excess weight (defined by WHO as a body mass index (BMI) of 25.0-29.9) or obesity (BMI >30.0) among individuals aged between 18 and 64 years - is one of the most common factors influencing the development of high blood pressure and diabetes. These conditions are, in turn, two important risk factors for cardiovascular diseases. The greater the BMI, the greater the risk of heart disease and stroke. In general, healthy nutrition and regular physical activity can reduce excess weight and obesity.
In 1998/99, the National Longitudinal Survey of Children and Youth reported that, based on international definitions, 37% of children aged 2 to 11 years were overweight and 18% were classified as obese. This was an increase from 34% overweight and 16% who were obese in 1994/95.
The CCHS reported that 47.5% of adults were overweight (BMI > 25.0) in 2000 (Figure 1-11). The percentage of overweight men and women has varied between 1994 and 2000, showing no consistent trend. In 2000, the percentage of men who were overweight was 1.4 times higher than women.
Figure 1 - 11
The 2000 CCHS also found that 15.2% of adults were obese (BMI > 30.0) - the same as in 1994. In the intervening years the percentage varied. The percentage of men who were obese increased from 13.5% to 16.1% while the percentage of women decreased from 16.8% to 14.2%.
According to the 2000 CCHS, the percentage of people who were overweight increased with age (Figure 1-12). The percentage of women who were overweight doubled between the 20-29 and 50-59 year age groups. Among men, the percentage in the older age group was 1.6 times higher than among the younger men.
Figure 1 - 12
The percentage of adults aged 20-59 years who were overweight was higher in the eastern provinces and Manitoba, Saskatchewan, Northwest Territories and Nunavut than in the overall Canadian population (Figure 1-13). Quebec and B.C. had the lowest percentages who were overweight.
Figure 1 - 13
Highest income women were less likely to be overweight than women in other income categories (Figure 1-14). Among men, the pattern was reversed, with the highest percentage overweight in the highest income category.
Figure 1 - 14
In 2000, women with less than secondary education were 1.5 times more likely to be overweight than women with a post-secondary degree (Figure 1-15). Among men, those with some post-secondary education had the lowest percentage that was overweight.
Figure 1 - 15
Inadequate Consumption of Fruits and Vegetables
A daily consumption of 5 to 10 servings of fresh fruits and vegetables is associated with a reduced risk of cardiovascular diseases. This benefit is related to the intake of natural vitamins, anti-oxidants and fibre. The potassium that such a diet provides has also been shown to be protective, particularly against strokes.
Although consumption of fresh fruits and vegetables tends to be seasonal with a higher intake during the summer months, it should be maintained at the recommended 5 or more daily servings year-round.
The data in this section include individuals aged 12+ years, the entire sample in the CCHS.
In 2000, 62.4% of Canadians 12 years of age and over (57.0% of women and 68.1% of men) consumed less than the recommended daily amount of fruits and vegetables, according to the CCHS. Among men, eating habits vary with age (Figure 1-16). The percentage who consumed less than the recommended daily amount rose in the 20-29 year age group and did not improve until after the age of 50. Among women, inadequate fruit and vegetable consumption was highest and similar in the age groups under the age of 50 years. Consumption improved among women after the age of 50.
Figure 1 - 16
Individuals in the Yukon, B.C. Ontario and Quebec reported better consumption of fruits and vegetables than individuals in all other provinces/territories (Figure 1-17).
Figure 1 - 17
Men and women with low incomes were more likely to consume less than the recommended daily amount of fruits and vegetables (Figure 1-18).
Figure 1 - 18
In 2000, there was very little difference in the consumption of the recommended daily amount of fruits and vegetables among men with various education levels (Figure 1-19). However, post-secondary education was associated with a lower percentage of women who consumed less than the recommended amount of fruits and vegetables.
Figure 1 - 19
High Blood Pressure
High blood pressure (defined as a systolic blood pressure >140 mmHg or diastolic blood pressure >90 mmHg) is a major risk factor for both stroke and coronary artery disease, peripheral vascular disease and congestive heart failure. It increases overall cardiovascular risk by two to three times. Research evidence strongly supports the benefits of treating high blood pressure to reduce the incidence of stroke, myocardial infarction, ischemic heart disease, vascular disease, renal diseases, heart failure and overall death rate.
Individuals who have excess weight, are physically inactive, use alcohol heavily, or have excessive salt intake are more likely to develop high blood pressure. High blood pressure is commonly associated with other metabolic cardiovascular risk factors such as insulin resistance, obesity, hyperuricemia, and dyslipidemia.
The data in this section begin with individuals aged 20+ years, a sub-sample of the CCHS, because screening is recommended to start at the age of 20 years.
Between 1994 and 2000, the prevalence of self-reported high blood pressure increased among both men and women (Figure 1-20). A higher percentage of women than men consistently reported high blood pressure throughout this period.
Figure 1 - 20
In 2000, the percentage of men and women who reported having high blood pressure increased with age (Figure 1-21). After the age of 50 years, the percentage of women was higher than men.
Figure 1 - 21
In 2000, a higher percentage of adults in the eastern provinces reported having high blood pressure compared to all other provinces and territories combined (Figure 1-22). The percentage in northern territories, B.C. and Alberta was lower than in Canada as a whole.
Figure 1 - 22
A higher percentage of men in the lower and lower middle income categories than in the upper income categories reported having high blood pressure (Figure 1-23). Among women, the percentage decreased with increased income. The percentage of women reporting high blood pressure was significantly higher than men in all income categories except the highest.
Figure 1 - 23
In 2000, the percentage of women and men who reported having high blood pressure was highest among those with less than secondary school education - 2.9 and 1.7 higher than women and men, respectively, with a post-secondary degree (Figure 1-24).
Figure 1 - 24
Early Detection of High Blood Pressure
High blood pressure is often silent and usually detected only through screening. As a result, the Canadian Task Force on Preventive Practices recommends that all adults aged 20+ years have their blood pressure assessed every two years, and more frequently if additional risk factors are present.
According to the National Population Health Survey (NPHS) and CCHS, a high percentage of adults (> 80%) reported having their blood pressure measured between the years 1994 and 2000 (Figure 1-25). The percentage among men had slightly increased since 1994.
Figure 1 - 25
The percentage of men and women who had their blood pressure checked increased with age in 2000 (Figure 1-26). Men between 20 and 39 years of age were much less likely than women to have their blood pressure assessed. (Women in this age group visit their physicians for contraception and prenatal care. As a result, their blood pressure is checked more often than men.) The gap narrowed with increasing age until the 70+ year age group, where the percentages were virtually equal.
Figure 1 - 26
According to the 2000 CCHS, a very high percentage of Canadian adults in all provinces reported having their blood pressure checked in the previous 2 years (Figure 1-27). The percentage was lowest in Nunavut and the Northwest Territories.
Figure 1 - 27
In 2000, a slightly higher percentage of adults in the highest income category compared to those in other income categories reported having their blood pressure checked in the previous 2 years (Figure 1-28).
Figure 1 - 28
The percentage of men and women who reported having their blood pressure measured in the previous 2 years varied little by education level (Figure 1-29). A slightly lower percentage of those with less than a secondary school education than those who had completed secondary school had their blood pressure checked. The pattern reversed between those with some post-secondary education and those who had completed post-secondary education.
Figure 1 - 29
Diabetes
Adult onset diabetes is a significant risk factor for the development of high blood pressure, stroke, and heart and vascular disease, particularly in women. Diabetes not only increases the incidence of cardiovascular diseases but adversely influences outcomes as well. Individuals with diabetes have a higher mortality rate from heart disease.
Maintaining a healthy weight through healthy nutrition and regular physical activity can prevent diabetes. Effective management of diabetes can decrease the risk of cardiovascular disease and other diabetes-associated complications, such as peripheral vascular disease, eye problems and kidney disease.
This section includes individuals aged 20+ years with adult onset (Type 2) diabetes. The CCHS does not include children less than 12 years of age to determine Type 1 or child onset diabetes.
The prevalence of self-reported diabetes among Canadian adults increased between 1994 and 2000: by 32% among men and 19% among women (Figure 1-30).
Figure 1 - 30
The percentage of men in the general population who reported having diabetes increased with age in 2000 (Figure 1-31). After the age of 50 years, the percentage of men with diabetes was higher than the percentage of women.
In 2000, the percentage of adults who reported having diabetes in Newfoundland, Nova Scotia and New Brunswick was higher than the percentage for all of Canada (Figure 1-32). The percentage in Alberta, Northwest Territories and Nunavut was lower. (The smaller sample sizes in some provinces/territories made it difficult to detect statistically significant differences between their jurisdictions and the overall Canadian population.)
Figure 1 - 31
Figure 1 - 32
Men and women in the upper middle and highest income categories had a much lower prevalence of self-reported diabetes than their counterparts in the lower middle and lower categories (Figure 1-33).
Figure 1 - 33
In 2000, the percentage of both men and women with less than secondary education who reported having diabetes was 2.3 times higher than the other education categories (Figure 1-34).
Figure 1 - 34
Ethnicity
Research among South Asian-born and Chinese-born Canadians has identified different mortality rates from cardiovascular diseases compared to individuals born in Canada.
New immigrants may be a healthy group to begin with, but as they adopt unhealthy lifestyles they develop increased rates of cardiovascular diseases. Some ethnic groups, such as South Asians and Eastern Europeans, are particularly vulnerable to heart disease while Chinese are particularly vulnerable to stroke (less so to heart attacks). Preventive programs should be targeted at ethnic groups with culturally adapted messages, using language and media that are likely to reach them. Research is needed to identify any special genetic predispositions to heart disease and stroke among various ethnic groups and to develop effective interventions.
The CCHS provides information on risk factors by ethnicity (Table 1-3).
In 2000, individuals with Eastern European ethnicity were less likely to be physically inactive than the Canadian population as a whole. Those with South and Southeast Asian backgrounds were more likely to be physically inactive.
In 2000, Canadians of Chinese or Southeast Asian ethnicity were more likely than the overall Canadian population to eat less than the recommended daily amount of fruits and vegetables.
Canadians of Chinese, Southeast Asian and South Asian backgrounds were much less likely to be overweight (BMI ³ 25.0) than the Canadian population as a whole.
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Table 1-3 Risk Factors for Heart Disease and Stroke among Adults Aged 20+ Years of Various Ethnic Backgrounds, Canada, 2000 |
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Risk Factor |
Percent of Population with Risk Factor |
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|
Chinese |
South |
Southeast Asian |
Eastern European |
Canadian |
|
Tobacco Smoking (Daily) |
9.9 |
6.4 |
15.3* |
22.8 |
22.7 |
|
Physical Inactivity |
63.3 |
67.0 |
73.5 |
51.9 |
56.5 |
|
Overweight (BMI > 25.0) |
18.7 |
40.0 |
22.7 |
50.7 |
47.5 |
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Consumed Less than Recommended Fruits & Vegs |
70.5 |
61.6 |
67.2 |
62.0 |
62.8 |
|
High Blood Pressure |
11.2 |
11.4 |
10.3* |
15.2 |
14.4 |
|
Diabetes |
3.4 |
5.6 |
2.8* |
4.2 |
4.7 |
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* Interpret with caution: based on small sample size Source: Statistics Canada, Canadian Community Health Survey |
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Aboriginal Peoples
In 2000, Aboriginal adults in Canada aged 20+ years were more likely than the Canadian population as a whole to be overweight (54.8% versus 47.5%) and to smoke (41.6% compared to 22.7%). They also were more likely to consume less than the recommended daily intake of fruits and vegetables (66.7% versus 62.8%).
On the other hand, Aboriginal Peoples were less likely than the overall Canadian population to be physically inactive (52.6% versus 56.5%) and less likely to report having high blood pressure (11.5% compared to 14.4%). The proportions that reported having diabetes were similar: (4.9% among Aboriginals compared to 4.7% for all of Canada). The results of the CCHS may reflect that its survey excluded individuals living on reserves. Other studies have found the prevalence of diabetes to be much higher among the Aboriginal Peoples.
In addition, the Aboriginal Peoples are younger than the Canadian population as a whole. As a result, since prevalence of diabetes increases with age, the Canadian population included in the survey will have a higher percentage of people with diabetes than the Aboriginal People included in the survey. The comparison between the two groups may, therefore, be skewed.
Dyslipidemia
Abnormally elevated cholesterol, low density lipoproteins (LDL) and triglycerides, and low levels of high density lipoproteins (HDL) are important risk factors for the development of vascular disease, particularly for coronary artery disease. Elevated levels of total serum cholesterol and low density cholesterol (LDC) are important risk factors for all types of stroke including stroke due to carotid artery disease. Pharmacological treatment of high blood cholesterol levels has proven to be very valuable in the management of coronary artery disease, reducing acute myocardial infarction by approximately 25% over 4 years in most studies. Pharmacological therapy has been shown to reduce the rate of stroke as well as coronary heart disease mortality.
According to the 1985-1990 Heart Health Surveys:
· 45% of men and 43% of women had a total plasma cholesterol level above the desirable level of 5.2 mmol/L;
· 30% of men and 27% of women were in the moderate risk group (5.2-6.1 mmol/L) and 18% and 17% respectively were in the highest risk group (> 6.2 mmol/L); and
· the proportion of men and women with a high cholesterol level (>5.2 mmol/L) increased with age, almost doubling from the 25-34 year age group to 35-44 year age-group among men and from the 35-44 year age group to age 45-54 year age group among women.
More current data are needed in order to assess whether progress has been made in decreasing the proportion of the population with high cholesterol levels.
Discussion
Canadians run a high risk of developing cardiovascular diseases: 8 out of 10 individuals have at least one of the following risk factors - smoking, physical inactivity, being overweight, high blood pressure and diabetes – and 1 in 10 have three or more. As a result, unless community interventions with a sufficient preventive impact are implemented, the cardiovascular epidemic will continue. Addressing these risk factors will prevent not only cardiovascular diseases, but also many other chronic diseases that share the same risk factors.
For some risk factors, the trends are encouraging. Both physical inactivity in the adult population and smoking in general have decreased over the past 8 years, based on self-reported data. Unfortunately, the trends among other risk factors continue to give cause for concern. The percentage of the population who are overweight has shown little change, and in fact, obesity is increasing among men. In addition, the prevalence of both self-reported high blood pressure and diabetes has increased.
Young people carry a high level of risk for cardiovascular diseases. Nearly two-fifths of teenaged girls are physically inactive. Over one-quarter of men and women in their twenties are overweight. Among young women in their later teens (18 and 19 years), 1 in 5 smokes cigarettes daily; among young men in the same age group, the statistic is nearly 1 in 4. Lifestyle habits that are formed in this early stage tend to be continued through life.
Risk factors differ between men and women. Women tend to be more physically inactive and to report having high blood pressure. More men than women smoke. They are more likely to consume less than the recommended amount of fruits and vegetables and to be overweight.
The prevalence of all risk factors varies by region. In comparison to Canada as a whole, British Columbia tends to have a lower prevalence of all risk factors, while prevalence in Newfoundland tends to be higher. In spite of this, the previous east-west gradient in risk factors as seen in past reports has become muted, with some prairie provinces having higher rates of risk factors and some eastern provinces having lower rates of risk factors than other provinces or territories (provincial rates of cardiovascular disease have been adjusted for age.)
A major limitation of the existing data is its lack of physical and biochemical measures of cardiovascular risk. Most provinces have not repeated the Heart Health Surveys that were conducted between 1985 to 1990, leaving a critical void in information about the detection and control of high blood pressure and dyslipidemia in Canada. In addition, we must rely on self-reported weight and height to estimate the prevalence of being overweight in the population.
Determining the prevalence of diabetes in the population presents a challenge. The approach used in this report relies on self-reports of diabetes having been diagnosed by a physician. This method has two limitations. First, people may not know that they have diabetes; and second, the criteria in making the diagnosis vary among physicians. A second approach uses administrative data to estimate the percentage of the population with diabetes. The National Diabetes Surveillance System (NDSS) uses this approach. Its report is available at http://www.hc-sc.gc.ca/pphb-dgspsp/ccdpc-cpcmc/diabetes-diabete/english/index.html.
Implications for Action
· Develop policies and implement community level and national programs with a sufficient preventive dose to decrease the high prevalence of cardiovascular disease risk factors.
· Implement policies and programs to encourage the adoption of healthy behaviours among children and youth.
· Conduct periodic surveys of nationally representative samples that include physical and biochemical measures to assess the prevalence of hypercholesterolemia, high blood pressure, diabetes and being overweight.