Chapter 2: Diabetes in Canada: Facts and figures from a public health perspective – Health impact

Chapter 2 – The health impact of diabetes on Canadians

Introduction

Diabetes can lead to many complications, including cardiovascular disease, vision loss/blindness, kidney failure, nerve damage, problems with pregnancy, oral disease and depression. These conditions contribute significantly to reduced quality of life, work limitations, and increased risk of death; they also greatly increase the demand for health care resources and add to the costs of diabetes for society (Chapter 3). Although the rates of many complications among people with diabetes have stabilized or decreased in recent years, the increase in the number of individuals with diabetes has led to a continued rise in the number of individuals affected by its complications.^{Footnote 1} Fortunately, it is often possible for individuals with diabetes to live healthy lives and delay or prevent complications through the management of blood glucose, blood lipids and blood pressure levels through lifestyle changes and medication.

Managing diabetes and its complications

The goals of diabetes management for individuals with type 1 and type 2 diabetes alike are to eliminate the symptoms and short-term risks of high or low glycemic levels, and to prevent or at least delay the progression of long-term complications through early detection and treatment. In 2008, the Canadian Diabetes Association published the updated Clinical practice guidelines for the prevention and management of diabetes in Canada,^{Footnote 2} providing evidence-based guidelines for optimal diabetes management. Healthy weights, regular physical activity, smoking cessation (where applicable), as well as aggressive control of blood sugar, blood pressure and blood lipid levels are all recommended by the Canadian Diabetes Association guidelines as ways to prevent or slow the progression of diabetes complications.

The association between hyperglycemia and increased diabetes complications is well known, making glycemic control the cornerstone of diabetes management. When blood sugars are poorly managed, diabetes can increase the risk of infection, delay wound healing, and lead to diabetic ketoacidosis. It can also increase the development and progression of micro and macro-vascular complications. These complications are more common among individuals who have been living with diabetes for many years, whose diabetes is poorly managed or who were living with previously undiagnosed diabetes. Maintaining glycemic levels within the range recommended by a physician can help prevent the development of complications, slow their progression, and improve prognosis. Although medication may be necessary, lifestyle changes alone can help some individuals with type 2 diabetes to maintain healthy glycemic levels.

Optimal management relies on both self-management by the individual and care from health professionals, including doctors, nurses, pharmacists, dieticians, and diabetes educators. However, the gap between recommended care, as per the Canadian Diabetes Association guidelines, and actual practice has been found to vary according to the type of care.^{Footnote 3-5} Poor management may be the result of limited access to health care providers or the required medications or treatments, as well as the inability to self-manage due to other competing illnesses or demands. In 2007, the CCHS collected additional data from individuals who self-reported a diagnosis of diabetes, and found that 81% of respondents indicated that their HbA1C levels had been checked by a physician in the past year. Individuals who reported using insulin were more likely to have their HbA1C levels tested than their counterparts who reported not using insulin (87% versus 80%).^{Footnote 3} However, a Canadian study looking at diabetes care in family practices found that one in two Canadians with type 2 diabetes did not have their glycemic levels within established targets.^{Footnote 6} The Survey on Living with Chronic Diseases in Canada, which was sponsored by the Public Health Agency of Canada and administered by Statistics Canada, was conducted in 2010-2011 on a population with self-reported diabetes. This cross-sectional survey will provide a national picture of self-reported glycemic control and management strategies used by Canadians with diabetes.

Medication use

Because type 2 diabetes is progressive, most people with the disease eventually require medication to help control glycemic levels. Type 2 diabetes is usually treated with oral medications, at least in its early stages. Insulin, which is given by injection, is required by all individuals with type 1 diabetes since they are unable to produce insulin on their own, but it may also be prescribed to individuals with type 2 diabetes. In 2009-2010, 89.7%^{Footnote i} of individuals aged 12 to 19 years and 85.1% of individuals aged 20 years or older with diabetes reported being on at least one oral medication, insulin, or both (Table 2-1). The dispensing of diabetes medication has increased steadily over the last decade (Figure 2-1).

Figure 2-1. Number of units of diabetes medications, by medication type, Canada^†, 2005 to 2009

† Data for the Territories were unavailable. ‡ Incretin agents consist of two products: Januvia was launched in December 2007 and Janumet in October 2009. Source: Public Health Agency of Canada (2010); using 2005 to 2009 data from CompuScript (IMS Health).

[Click to enlarge Figure 2-1]

A relationship between the type of medication used and quality of care has been shown; individuals on insulin were more likely to receive the recommended level of care from a health professionalFootnote ii than those not on insulin.Footnote 3;Footnote 5 On the other hand, quality of life has been seen to decrease for individuals with type 2 diabetes who use insulin. However, individuals with type 2 diabetes who use insulin are often prescribed insulin due to the progression of the disease and the resulting failure of lifestyle or oral medication management or because complications appeared.Footnote 7 A study of people with type 1 diabetes found no association between quality of life and intensity of insulin injection regime.Footnote 8

Complications associated with diabetes

Despite multi-faceted efforts to manage diabetes, the disease can lead to a variety of short-term and long-term complications. Short-term complications of diabetes (such as infection, slow wound healing, diabetic ketoacidosis) can arise from hyperglycemia or from treatments for diabetes (particularly insulin) leading to glycemic levels that are too low (hypoglycemia). These short term complications can be life-threatening if they are not treated quickly. Diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar nonketotic syndrome (HHNS) are two complications resulting from severe hyperglycemia which can lead to death. Hypoglycemia can lead to confusion, falls, and loss of consciousness, and in extreme cases, also death.

Many long-term complications of diabetes that ensue from hyperglycemia, hypertension, and dyslipidemia are linked to damage to large (macrovascular) and small (microvascular) blood vessels in the body. This damage affects the function of organs, including the heart, kidneys, eyes, and the nervous system. In 2008/09, Canadian adults with diabetes were more likely than those without diabetes to be hospitalized with other health problems affecting these organs (Figure 2-2). Good metabolic control (including glycemia, blood pressure, and blood lipids) reduces the development and progression of this type of damage. Other complications associated with diabetes include problems with pregnancy, such as preterm birth and macrosomia (large newborn), oral disease, and depression.

Figure 2-2. Prevalence rate ratios^† of complications among hospitalized individuals^‡ aged 20 years and older, by diabetes status, Canada, 2008/09

† Rate ratios based on rates age-standardized to the 1991 Canadian population. ‡ A person with diabetes hospitalized with more than one complication was counted once in each category, except for cases of acute myocardial infarction, where regardless of multiple counts in the acute myocardial infarction category, the individual was counted only once under the broader ischemic heart disease category. Source: Public Health Agency of Canada (August 2011); using 2008/09 data from the Canadian Chronic Disease Surveillance System (Public Health Agency of Canada).

[Click to enlarge Figure 2-2]

Cardiovascular disease

Diabetes significantly increases the risk of cardiovascular disease — a condition encompassing heart disease, stroke, and peripheral vascular disease. Individuals with diabetes are two to four times more likely to develop cardiovascular disease than those without.^{Footnote 9} Cardiovascular disease is the most commonly reported condition in Canadians with diabetes, the most common cause of death in individuals with type 2 diabetes,^{Footnote 10} and the leading driver of health care costs for people with diabetes.^{Footnote 11} It has been estimated that if diabetes were eliminated from the world population, there would be a 19.1% global decrease in the rate of acute myocardial infarction among females, and a 10.1% global decrease among males.^{Footnote 12}

Diabetes leads to premature narrowing of the arteries (atherosclerosis), which can damage the coronary blood vessels and lead to unstable angina and acute myocardial infarction.^{Footnote 13;Footnote 14} An individual's risk of cardiovascular disease can increase even before diabetes is diagnosed, when glycemic levels are elevated but not high enough to manifest symptoms or to meet the diagnostic criteria for diabetes. In addition, many risk factors for cardiovascular disease, such as overweight, hypertension and dyslipidemia, are more prevalent among individuals with, or at risk of, diabetes (Chapter 4). When these risk factors are present in individuals with diabetes, the risk of cardiovascular disease is much higher than when either diabetes or risk factors are present alone. Because diabetes and cardiovascular disease share many risk factors, it is sometimes difficult to disentangle cases of comorbidity from the complications of diabetes.

In 2009-2010, 22.7% of Canadians aged 20 years and older with diabetes reported having heart disease, compared to 6.0% in the population without diabetes.^{Footnote 15} In 2008/09, 64.5% of adults with diagnosed diabetes also had diagnosed hypertension. When adjusted for age differences, this was twice the number of diagnosed hypertension cases in a population without diabetes.^{Footnote 16} Similarly, after age adjustment, cardiovascular disease hospitalizations were three times higher in individuals with diabetes than in those without diabetes.^{Footnote 17}

Eye disease (diabetic retinopathy, cataracts and glaucoma)

Diabetic retinopathy, which can cause blindness, results when hyperglycemia damages the small blood vessels in the retina of the eye. In general, there are no symptoms of retinopathy until it has advanced enough to cause acute vision loss due to bleeding or retinal detachment. In some people with diabetes, swelling in the retina from leaking blood vessels may cause a gradual decline in vision. If undetected or left untreated, this can progress and lead to permanent eye damage and blindness. Early detection and appropriate treatment with laser photocoagulation can prevent vision loss. In 2006, it was estimated that close to 500,000 Canadians had some form of diabetic retinopathy. Of these, 100,000 had a vision-threatening form of the disease (defined as severe retinopathy, diabetic macular edema, or both), and 6,000 were already blind from the disease.^{Footnote 18}

Poorly controlled hyperglycemia and hypertension increase the risk of diabetic retinopathy, while effective treatment of these two factors has been shown to slow its progression.^{Footnote 19} The risk of retinopathy increases with the number of years diabetes has been present.^{Footnote 20} At time of diagnosis, up to 21% of patients with type 2 diabetes already have some form of diabetic retinopathy.^{Footnote 21} For most of these individuals, the condition is not yet sight-threatening, but should be monitored closely by a specialist. In the first 20 years after a diagnosis of diabetes, almost all individuals with type 1 diabetes and more than 60% of individuals with type 2 diabetes develop some form of retinopathy.^{Footnote 21} Cataracts and glaucoma, two other eye diseases that lead to impaired vision, are also associated with diabetes, although the causal relationship is not yet understood.^{Footnote 22-25}

As the population ages and the prevalence of diabetes rises, the number of individuals affected by vision loss and its associated costs will also increase.^{Footnote 26} This underscores the importance of ongoing screening and effective treatment for retinopathy. The Canadian Diabetes Association clinical practice guidelines provide specific recommendations on the frequency and methods of screening individuals with type 1 and type 2 diabetes for retinopathy.^{Footnote 2} Results from the 2007 CCHS showed that only 66% of individuals with diabetes had an eye exam in the last two years as recommended in the clinical practice guidelines.^{Footnote 3;Footnote 5}

Kidney disease (nephropathy)

Diabetic nephropathy results when hyperglycemia damages the blood vessels that filter blood in the kidneys. Since type 2 diabetes may remain undiagnosed for a long period of time, kidney damage often begins before diabetes is diagnosed. In its early stages, damage to the kidney allows blood proteins to leak into the urine. This leakage is detectable only by laboratory testing of urine. As damage progresses, kidney function can be compromised, eventually resulting in kidney failure and end-stage renal disease. At that point, the kidney no longer works effectively and the individual requires dialysis or a kidney transplant for survival.

In 2008/09, individuals with diabetes were 5.9 times more likely to be hospitalized with renal disease and 12.0 times more likely to be hospitalized with end-stage renal disease than individuals without diabetes (Figure 2-2). In 2009, diabetes was reported as the primary cause of end-stage renal disease in 34% of the incident cases in Canada, continuing to be the country's most commonly reported primary cause of the disease (Figure 2-3). The number of Canadians starting renal replacement therapy (dialysis or transplant) has been increasing steadily since the mid-1990s.^{Footnote 27} The primary reason for this increase has been attributed to the growing number of people with diabetes, rather than a higher proportion of individuals with diabetes being diagnosed with end-stage renal disease or an increasing willingness to dialyse people with diabetes.^{Footnote 28} As the number of people with diabetes continues to rise, so too will the demand for dialysis services.

Figure 2-3. Number of incident cases of end-stage renal disease, by primary diagnosis, Canada, 2000 to 2009

Source: Public Health Agency of Canada (2011); adapted from Canadian Institute for Health Information. Canadian Organ Replacement Register Annual Report: Treatment of End-Stage Organ Failure in Canada, 2000 to 2009. 2011. Ottawa.

[Click to enlarge Figure 2-3]

Individuals with kidney disease are also at elevated risk of cardiovascular disease mortality.^{Footnote 29} Kidney disease and cardiovascular disease share common risk factors, including hyperglycemia, hypertension and hypercholesterolemia, making the treatment and management of these factors a priority for the prevention of both conditions. Screening for kidney disease and its risk factors is an important part of diabetes management and a key focus of the Canadian Diabetes Association clinical practice guidelines.^{Footnote 2} In 2007, 74% of CCHS respondents with diabetes indicated that they received a urine protein test in the past year, as recommended by guidelines.^{Footnote 3} Screening is important because, when identified early, medications and interventions to control blood sugar and blood pressure have been shown to delay or prevent the progression of kidney disease.^{Footnote 30}

Nerve damage (neuropathy)

In individuals with diabetes, nerve damage most commonly results from reduced blood flow to nerves, which in turn is the result of damage to blood vessels caused by hyperglycemia. Without sufficient blood to provide oxygen and remove toxins, nerve structure and function are impacted. Pain, tingling and numbness are the symptoms most commonly associated with nerve damage. Other symptoms include erectile dysfunction and delayed gastric emptying (gastroparesis). Most neuropathies are asymptomatic, but numbness and the inability to perceive pain or injury are dangerous and are a common cause of foot ulceration.

Lower extremity complications and amputation

In 2008/09, Canadian adults with diagnosed diabetes were almost 20 times more likely to be hospitalized with non-traumatic lower limb amputations than their counterparts without diabetes (Figure 2-2). Indeed, there is a greater risk that even minor injuries can become infected because numbness – caused by nerve damage – can prevent an individual with diabetes from feeling the injury, and decreased blood flow – caused by peripheral vascular disease – can prevent healing once an injury occurs. Non-healing ulcers and deep-seated (bone) infections are the most common reasons for amputation.

Amputations are debilitating and can lead to increased morbidity, mortality, as well as increased treatment and hospitalization costs. Fortunately, many foot complications are preventable with proper foot care, including regular foot exams and aggressive treatment of infections.^{Footnote 2} In 2007, only 51% of individuals with diabetes surveyed in the CCHS met the clinical practice guidelines for physician foot examinations.^{Footnote 3;Footnote 5}

Complications during pregnancy

During pregnancy, glucose crosses the placenta freely, exposing the fetus to glycemic concentrations similar to those of the mother. Hyperglycemia has been associated with complications for both the fetus and the mother. Babies born to women with diabetes are more likely to experience congenital malformations,^{Footnote 31} poorer neonatal health, and macrosomia. All of these increase the likelihood of preterm delivery, caesarean section, and death.^{Footnote 32;Footnote 33} Women with diabetes during their pregnancy are at increased risk of developing hypertension and exacerbating other diabetic complications.^{Footnote 34} Careful glycemic control, both before conception and during pregnancy, has been shown to reduce the risk of complications.^{Footnote 35;Footnote 36}

Pregnancy complications are more likely in women with pre-existing diabetes (either type 1 or type 2) than in women who develop gestational diabetes during pregnancy.^{Footnote 37} In 2006, it was estimated that maternal diabetes was present in 5.1% of pregnancies resulting in live births in Canada (excluding Quebec). Of these, the majority (87.8%) were in women who developed gestational diabetes during pregnancy, while the remaining 12.2% were in women with pre-existing diabetes.^{Footnote 36}

In 2006/07, the rate of preterm delivery among women with pre-existing diabetes was 28.2%, more than three times as high as that among women without diabetes (7.9%) and more than double the rate among women with gestational diabetes (11.7%). Similarly, rates of macrosomia were higher in women with pre-existing diabetes (7.0%) than in women with no diabetes (1.9%) or gestational diabetes (3.2%), and the reverse association was observed for rates of small-for-gestational age (Figure 2-4).

Figure 2-4. Rate of preterm birth, small-for-gestational age, and macrosomia, by maternal diabetes status, Canada, 2006/07

Source: Public Health Agency of Canada (2011); adapted from Canadian Institute for Health Information. Too Early, Too Small: A Profile of Small Babies Across Canada. 2009. Ottawa.

[Click to enlarge Figure 2-4]

Oral disease (gingivitis, periodontitis)

Gingivitis, an inflammatory condition of the gums surrounding the teeth, and periodontitis, the destruction of the ligament, bone, and soft tissues that support the teeth, are two of the most serious dental conditions identified in individuals with diabetes.Footnote 38 For example, a study using American survey data found that adults with poorly controlled diabetes had a significantly higher prevalence of severe periodontitis than those without diabetes (odds ratio (OR): 2.90; 95% CI: 1.40, 6.03).Footnote 39 The pain, discomfort, and eventual tooth loss associated with these conditions can lead to poor diet, nutritional deficiencies, psychosocial problems, and an overall decline in quality of life. Historically identified as a complication of both type 1 and type 2 diabetes, periodontal disease has also been thought to increase the risk of developing type 2 diabetes because the body's inflammatory response to the periodontal bacteria is believed to contribute to insulin resistance.Footnote 40 In addition to gingivitis and periodontitis, individuals with diabetes have higher rates of dental caries and salivary dysfunction.Footnote 41

Mental illness

Depression is more common among people with diabetes than among those without^{Footnote 42;Footnote 43}, and has been identified as a complication of diabetes.^{Footnote 44} However, the causal relationship between these two conditions is still unclear, with the potential that the relationship may in fact be bi-directional.^{Footnote 45;Footnote 46} The stress of dealing with a diagnosis of diabetes can deteriorate an individual's mental health and lead to symptoms of depression. Furthermore, many complications associated with diabetes significantly impact the quality life of individuals and can also lead to depression. Vision loss alone has been strongly associated with depression.^{Footnote 47;Footnote 48}

In 2009-2010, while 7.0% (95% CI: 6.8-7.3%) of Canadians aged 20 years and older reported having a mood disorder such as depression, bipolar disorder, or mania, the prevalence was higher among individuals with diabetes (9.6%; 95% CI: 8.7-10.5%) than without (6.9%; 95% CI: 6.6-7.1%)Footnote iii.Footnote 15 Together, diabetes and depression can increase the risk of disability, complications, and mortality, and result in higher health care costs when compared to diabetes alone. Depression can lead to poorer diabetes self-care, obesity-promoting health behaviours and poorer glycemic control.Footnote 49 Further, some medications used to treat depression cause increases in body weight and in glycemic levels. Recognizing and treating mental illness among individuals with diabetes is especially important for effective disease management.Footnote 2

Other conditions

Other chronic conditions associated with type 1 diabetes include thyroid disease and celiac disease.^{Footnote 50} Chronic conditions associated with type 2 diabetes, mainly through their association with similar risk factors (obesity in particular) include osteoarthritis,^{Footnote 51} chronic obstructive pulmonary disease (COPD),^{Footnote 52} obstructive sleep apnea,^{Footnote 53} and cancer.^{Footnote 54} In 2009-2010, 36.5% (95% CI: 34.9-38.2%) of Canadians with diabetes aged 20 years and older reported having two or more serious chronic conditions (hypertension, heart disease, COPD, mood disorder, and/or arthritis) in addition to diabetes, and 12.5% (95% CI: 11.5-13.5%) reported having three or more.^{Footnote 15} The co-existence of other chronic conditions may hinder the management of diabetes, health services utilization, and health-related quality of life (HRQOL). In general, people with other chronic conditions in addition to diabetes have poorer HRQOL than those without these conditions.^{Footnote 55-57}

The impact on quality of life

Diabetes and its complications affect people's lives and those of family members in many ways. Making lifestyle changes; managing hyperglycemia, hypertension, and dyslipidemia, as well as other complications and comorbidities; taking steps to help prevent and treat complications; losing time from school and work; and paying for supplies and drugs can place a burden on individuals with diabetes and their families. These stresses can affect the quality of life and overall health of an individual.

Self-rated health status

How people perceive their general health provides a good indication of their quality of life. In 2009-2010, nearly two-fifths (39.1%) of Canadians aged 20 years and older who reported having diabetes rated their health as "fair" or "poor", compared to a tenth of the adult population without diabetes (10.3%). Adults aged 30 to 39 years with diabetes were six times more likely to rate their health as "fair" or "poor" than individuals of the same age without diabetes. In the oldest age groups, individuals with diabetes were about twice as likely to self-report their health as fair or poor (Figure 2-5).

Figure 2-5. Prevalence and rate ratios of self-reported health as "fair" or "poor" among individuals aged 20 years and older, by age group and diabetes status, Canada, 2009-2010

† Marginal variance estimate; data should be interpreted with caution. Source: Public Health Agency of Canada (2011); using 2009-2010 data from the Canadian Community Health Survey (Statistics Canada).

[Click to enlarge Figure 2-5]

Mortality trends associated with diabetes

Diabetes is not usually the primary cause of death, but many of its complications are associated with premature death.^{Footnote 10} Because diabetes is not commonly recorded as the cause of death on a death certificate, vital statistics data significantly underestimate the relationship between diabetes and mortality in Canada. For example, in 2007, diabetes was recorded as the primary cause of death on the death certificate of only 3.1% (7,394) of all deaths in Canada,^{Footnote 58} even though more than a quarter (29.9%, or 69,992) of all individuals who died in 2008/09 had been diagnosed with diabetes.^{Footnote 17} Using CCDSS data, it is estimated that at least one in every ten deaths (11.9%) in the Canadian adult population (aged 20 years or older) was attributable to diabetes in 2008/09. Males had a greater population attributable risk (12.6% of all deaths) compared to females (11.1%). Although the exact number of deaths attributed to diabetes is difficult to ascertain, it is clear that individuals with diabetes are at elevated risk of premature death compared to people without diabetes.

People with diabetes are more likely to die prematurely than people without diabetes in every age group. In younger Canadians (aged 20 to 39 years), all-cause mortality rates were 4.2 to 5.8 times higher among individuals with diabetes. In the 40 to 74 year age group, all-cause mortality rates were two to three times higher among people with diabetes (Figure 2-6).

Figure 2-6. All-cause mortality rates and rate ratios among individuals aged 20 years and older, by diabetes status, Canada, 2008/09

Source: Public Health Agency of Canada (June 2011); using 2008/09 data from the Canadian Chronic Disease Surveillance System (Public Health Agency of Canada).

[Click to enlarge Figure 2-6]

Higher mortality rates among individuals with diabetes resulted in noticeable decreases in life expectancy at all ages. Children aged one to 19 years with diagnosed diabetes had a life expectancy ten to 11 years less than children without diabetes. Working-aged adults (aged 20 to 64 years) with diabetes had a life expectancy five to ten years less than adults of the same age without diabetes.^{Footnote 17} When considering the morbidity burden experienced by individuals with diabetes, their health adjusted life expectancy (HALE)^{Footnote iv} at birth was also lower compared to those without diabetes at all ages. Overall, it was estimated that females with diabetes would lose 11.1 years in HALE, while males would lose 10.8 years (Figure 2-7).

Figure 2-7. Life expectancy (LE) and health-adjusted life expectancy (HALE) among individuals from birth and older, by age group, sex, and diabetes status, Canada^†, 2004/05 to 2006/07

† Data for Quebec, Nunavut and the Northwest Territories were unavailable. Source: Public Health Agency of Canada (2011); adapted from Public Health Agency of Canada Steering Committee on Health-Adjusted Life Expectancy. Health-Adjusted Life Expectancy in Canada: 2010 Report by the Public Health Agency of Canada. In press. Ottawa.

[Click to enlarge Figure 2-7]

Looking ahead

The projected increase in the prevalence of diabetes in the coming years suggests an overall continued rise in the number of individuals affected by complications. Individuals affected by diabetes complications may experience reduced quality of life, limitations in their ability to work, and are at risk for premature death. This underscores the importance of managing blood sugar, blood lipids and blood pressure levels through lifestyle changes and medication.

Reference list