Introduction: Diabetes in Canada: Facts and figures from a public health perspective
Introduction – Diabetes surveillance in Canada
This report – Diabetes in Canada: Facts and figures from a public health perspective – provides a comprehensive look at diabetes and its impact on the Canadian population. The data presented are intended for health professionals, non-government organizations (NGOs), policy makers, academics, and other interested readers.
Impact on human physiology
Diabetes is a chronic disease that occurs when the body is either unable to sufficiently produce or properly use insulin. Insulin, a hormone secreted by beta cells in the pancreas, enables the cells of the body to absorb sugar from the bloodstream and use it as an energy source. If left uncontrolled, diabetes results in consistently high blood sugar levels, a condition known as hyperglycemia. Over time, hyperglycemia can damage blood vessels, nerves, and organs such as the kidneys, eyes and heart, resulting in serious complications and, ultimately, death. Hypertension and hyperlipidemia, which often accompany diabetes and accelerate damage to blood vessels, are also important targets for control.
Types of diabetes
Diabetes occurs in several forms; type 1, type 2 and gestational are the most common (Box I-1). Although all types of diabetes are characterized by the body's inability to maintain appropriate glycemic levels, they may differ in their causes, treatments and complications. It is estimated that 90% to 95% of Canadians with diabetes have type 2 diabetes, while 5% to 10% have type 1 diabetes. Gestational diabetes, which develops during pregnancy and typically disappears afterwards, has been detected in approximately 3% to 5% of all pregnancies that resulted in a live birth.Footnote 1 Footnote 2 Pre-diabetes describes a condition that indicates increased risk of type 2 diabetes. Not all individuals with pre-diabetes will develop diabetes, but the chances increase if steps are not taken to manage it. Fortunately, recent studies have shown that changes in lifestyle (primarily diet, physical activity and weight management) can delay or halt the progression from pre-diabetes to diabetes.Footnote 3 Footnote 4 Footnote 5
Box I-1. Main forms of diabetes
- Type 1 diabetes, once known as "juvenile diabetes" or also referred to as "insulin-dependent diabetes mellitus", is an autoimmune disease in which the body's immune system attacks and destroys the insulin-producing cells of the pancreas, thereby leaving the individual dependent on an external source of insulin for life. Type 1 diabetes typically arises in people under the age of 40, most often in children and youth.
- Type 2 diabetes, also referred to as "non-insulin-dependent diabetes mellitus", is a metabolic disorder that occurs when the pancreas does not produce enough insulin and when the body does not properly use the insulin it makes. The risk of type 2 diabetes is higher among people who are overweight or obese, physically inactive and of certain ethnic populations. While the onset of type 2 diabetes typically occurs in adults over the age of 40, it can occur at younger ages, and is seen even in children and youth.
- Gestational diabetes occurs when hyperglycemia develops during pregnancy. Although elevated glycemic levels typically disappear following delivery, females diagnosed with gestational diabetes are at increased risk of developing type 2 diabetes within five to ten years.
- Other types of diabetes are uncommon. They include those associated with genetic defects, other diseases, infections and specific medications that affect the body's ability to produce or respond to insulin, resulting in hyperglycemia.
Measurements of glycemic levels (Box I-2) are used to determine if an individual has, or is at risk of, diabetes. The criteria used to diagnose diabetes are defined in the Canadian Diabetes Association clinical practice guidelines. Individuals with glycemic levels that are higher than normal, but not yet high enough to meet the criteria for a diabetes diagnosis, are often diagnosed with pre-diabetes, characterized by impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT).
Box I-2. Clinical criteria for the diagnosis of impaired fasting glucose, impaired glucose tolerance and diabetes
|Fasting† plasma glucose (mmol/L)||Two-hour plasma glucose in a 75g oral glucose tolerance test (mmol/L)||Casual‡ plasma glucose (mmol/L)|
|Impaired fasting glucose||6.1 – 6.9||and||<7.8|
|Impaired glucose tolerance||<6.1||and||7.8 – 11.0|
|Impaired fasting glucose and impaired glucose tolerance||6.1 – 6.9||and||7.8 – 11.0|
||≥7.0||or||≥11.1||or||≥11.1; with symptoms of diabetes (polyuria, polydipsia, unexplained weight loss)|
† Fasting based on no caloric intake for at least eight hours.
‡ Plasma glucose measured at any time of the day without regard to the interval since the last meal.
Source: Public Health Agency of Canada (2011); adapted from Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2008 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes.2008;32(Suppl 1):S1-S201.
Diagnosing type 1 diabetes can be done by testing for markers of the autoimmune destruction of insulin-producing cells of the pancreas. These markers include islet cell antibodies, insulin autoantibodies, glutamic acid decarboxylase antibodies, and antibodies against tyrosine phosphatase.Footnote 6 The onset of type 1 diabetes is often quite rapid, while typically there is a gradual increase of hyperglycemia in type 2 diabetes. In this case, it can take years before glycemic levels are sufficiently high to present symptoms leading to a diagnosis of type 2 diabetes.Footnote 7 Consequently, many individuals who have type 2 diabetes spend a significant period of time unaware that they have the disease.Footnote 8 Footnote 9 Because of this, complications of diabetes often begin to develop before individuals are diagnosed. This highlights the importance of type 2 diabetes prevention and early detection.
The diabetes surveillance system
High quality surveillance data on health status, risk factors, health determinants, and health service utilization are essential for the planning and evaluation of effective policies and programs. The availability of high quality surveillance information on diabetes in Canada has increased substantially over the last decade. The Canadian Chronic Disease Surveillance System (CCDSS)Footnote i uses population-based administrative data from every province and territory to provide detailed, comparative information for assessing the scope, as well as the use of health services and health outcomes of chronic diseases, including diabetes. Data from population health surveys and vital statistics provide additional data on diabetes, its risk factors and complications. As this report uses multiple data sources, estimates may be reported for different periods of reference and age groups, and definitions may vary depending on the data source. Technical notes on these data sources (Box I-3) present these considerations.
Box I-3. National data sources and limitations
- Period of reference
- Specific conventions are used in this report to distinguish between different periods of reference. This format "200X/0Y" indicates a fiscal year running from April 1, 200X to March 31, 200Y. Data from the CCDSS are reported by fiscal year, on an annual basis.
- When the data collection spans over more than a year, the period of reference is reported as "200X-200Y". The Canadian Community Health Survey (CCHS) collects data annually, but merges samples from two consecutive years to increase the sample size. Similarly, the First Nations Regional Longitudinal Health Survey (RHS) collected data between 2008 and 2010, indicated as "2008-2010".
- Age groups
- When possible, standard age groups and cut-offs are used in this report. At times, standardization is not possible depending on the data source. Moreover, depending on the indicator reported, it may be preferable to exclude some age groups or it may not be possible to report on certain age groups due to small sample size.
- Confidence intervals
- The 95% confidence intervals presented with these data show an estimated range of values which are likely to include the true prevalence rate 19 times out of 20.
- Year of data
- Although published in 2011, estimates in this report refer to various years of data. This may be impacted by the frequency of the data collection of each data source. Further, additional lag time is required by the organization responsible for the data to fully process and release data. Finally, the Public Health Agency of Canada takes time to ensure the quality and accuracy of data, conduct and interpret analyses, and release the final report.
- Diabetes definitions
- In this report, "diabetes" refers to self-reported data or the disease in general. In the 2009-2010 CCHS, for example, the term "diabetes" indicates that an individual has self-reported a physician diagnosis of diabetes of either type 1 or type 2 by answering "yes" to the question: "Do you have diabetes?". To exclude cases of gestational diabetes, where respondents said that their diabetes was diagnosed during pregnancy ("Were you pregnant when you were first diagnosed with diabetes?") and that they did not have diabetes other than when pregnant ("Other than during pregnancy, has a health professional ever told you that you have diabetes?"), they were excluded from analyses.
- The term "diagnosed diabetes", which excludes individuals living with the disease but who have not yet received a diagnosis of diabetes by a health professional, is used when CCDSS data are reported. The CCDSS summarizes data on residents of Canada who have accessed the Canadian health care system. Diabetes is deemed diagnosed when there is, at minimum, one hospitalization or two physician claims with a diabetes specific code(s) over a two year period. The CCDSS case definition excludes women with gestational diabetes, and it does not distinguish between type 1 and type 2 diabetes.
- In all cases, description of diabetes excludes cases of undiagnosed diabetes in the population.
- Footnote 1
Canadian Institute for Health Information. Too early, too small: A profile of small babies across Canada. Ottawa, ON: Canadian Institute for Health Information; 2009.
- Footnote 2
Feig DS, Zinman B, Wang X, Hux JE. Risk of development of diabetes mellitus after diagnosis of gestational diabetes. CMAJ. 2008;179(3):229-234.
- Footnote 3
Benjamin SM, Valdez R, Geiss LS, Rolka DB, Narayan KMV. Estimated number of adults with prediabetes in the U.S. in 2000: Opportunities for prevention. Diabetes Care. 2003;26(3):645-649.
- Footnote 4
Knowler WC, Barrett-Connor E, Fowler SE et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346(6):393-403.
- Footnote 5
Tuomilehto J. Nonpharmacologic therapy and exercise in the prevention of type 2 diabetes. Diabetes Care. 2009;32(Suppl 2):S189-S193.
- Footnote 6
Kaufman FR. Type 1 diabetes mellitus. Pediatr Rev. 2003;24(9):291-300.
- Footnote 7
Leiter LA, Barr A, Belanger A et al. Diabetes Screening in Canada (DIASCAN) Study: Prevalence of undiagnosed diabetes and glucose intolerance in family physician offices. Diabetes Care. 2001;24(6):1038-1043.
- Footnote 8
Harris MI, Flegal KM, Cowie CC et al. Prevalence of diabetes, impaired fasting glucose, and impaired glucose tolerance in U.S. adults: The Third National Health and Nutrition Examination Survey, 1988-1994. Diabetes Care. 1998; 21(4);21:518-524.
- Footnote 9
Young TK, Mustard CA. Undiagnosed diabetes: Does it matter? CMAJ 2001:164(1);164:24-28.
- Footnote i
The CCDSS was formerly known as the National Diabetes Surveillance System (NDSS).
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