Chapter 5: Diabetes in Canada: Facts and figures from a public health perspective – Youth and children

Chapter 5 – Diabetes in children and youth

Introduction

Diabetes is one of the most common chronic diseases among children and youth. In 2008/09, the CCDSS reported 3,287 new cases of diagnosed diabetes (including both type 1 and type 2) among Canadians aged one to 19 years, bringing the total number of cases in children and youth to 25,693 (representing a prevalence rate of 0.3%) (Chapter 1, Table 1-1).

Historically, all cases of diabetes in young individuals were believed to be type 1 diabetes. However, for the last two decades, type 2 diabetes has been on the rise globally in this population. Currently, no population-based surveillance study has confirmed the ratio between the two types of the disease in children and youth in Canada. However, one study from British Columbia developed an algorithm to distinguish between type 1 and type 2 cases in administrative data, and estimated that approximately 90% of the cases among children and youth aged one to 19 years were of type 1 diabetes and 10% were of type 2 diabetes in 2006/07.^{Footnote 1} As the rates of obesity increase among children and youth, the rates of type 2 diabetes also increase. Therefore, the ratio of type 1 to type 2 in this population is likely to be impacted.^{Footnote 2}

Research suggests that both type 1 and type 2 diabetes are increasing worldwide in youth.^{Footnote 3} As both forms of diabetes are lifelong diseases, the early onset of either type increases the risk of related complications later in life, with lifelong implications for those with the disease and their families, as well as for the health care system and the Canadian economy. Although it is currently only possible to prevent type 2 diabetes, optimal management of both type 1 and type 2 diabetes is of primary importance to prevent negative consequences of either disease.

Type 1 diabetes

Most cases of type 1 diabetes are diagnosed during childhood and adolescence, and it is recognized that type 1 diabetes remains the predominant form of the disease in this population.^{Footnote 4} The onset can occur as early as during the first year of life, but generally the onset is most common between ten and 14 years of age.^{Footnote 5} No consistent gender pattern for the incidence of type 1 diabetes in youth was observed.^{Footnote 6}

Estimates of the number of children and youth who have type 1 diabetes in Canada are limited. Currently a national estimate is not available, and existing estimates vary widely accross provinces. Between 1989 and 2000, the annual incidence of type 1 diabetes among children aged 18 years and under in Quebec was 15 cases per 100,000 children.^{Footnote 7} Newfoundland and Labrador reported one of the highest incidence rates of type 1 diabetes in the world; for the period between 1987 and 2005, incidence among children aged less than 15 years was identified as 35 cases per 100,000 children. In children aged less than five years, boys (31.6 cases per 100,000 children aged less then five) were more likely to be affected than girls (19.1 cases per 100,000 children aged less than five).^{Footnote 8}

Rates of type 1 diabetes among children and youth have been on the rise globally.^{Footnote 9} Based on study analyses, Canada was found to have one of the highest incidence rates of type 1 diabetes for children under 14 years of age.^{Footnote 6 Footnote 10} In Canada, the average relative increase in incidence rates has been estimated at 5.1% per year between 1990 and 1999.^{Footnote 6} Children under the age of five were the fastest growing segment of the population with type 1 diabetes.^{Footnote 6 Footnote 10 Footnote 11}

Risk factors for type 1 diabetes

Type 1 diabetes is a multifactorial condition, characterized by the presence of autoimmunity against insulin producing cells. Although researchers have not yet identified all of the factors causing type 1 diabetes and the interactions among them, they believe genetic factors and environmental triggers are involved.^{Footnote 9 Footnote 12} The increasing trend of type 1 diabetes observed in many countries is believed to be associated with a number of factors, such as changes in early feeding patterns, early growth in the first year of life, and hygiene practices such as the use of antibacterial disinfectants, among other influences. Other findings that support the theory of genetic and environmental associations include:

• Type 1 diabetes is most common among children and youth of northern European descent.^{Footnote 13}
• First-degree relatives (parents, offspring, siblings) of individuals with type 1 diabetes have a tenfold greater risk of developing type 1 diabetes than the rest of the population.^{Footnote 14} In particular, children of fathers with type 1 diabetes are at a greater risk of developing type 1 diabetes than children of mothers with the disease.^{Footnote 15}
• No single infection has been linked to an increase in type 1 diabetes,^{Footnote 16} but viruses such as enteroviruses^{Footnote 17} and dietary microbial toxins^{Footnote 18 Footnote 19} may be factors in the development of type 1 diabetes.
• Studies have identified a number of factors that might reduce the risk of developing type 1 diabetes, such as breastfeeding and vitamin D. Less exposure to the sun^{Footnote 20 Footnote 21} (a source of vitamin D) and vitamin D deficiency^{Footnote 22 Footnote 25} are associated with higher rates of type 1 diabetes. Some research has suggested that breastfeeding has a protective effect against the development of type 1 diabetes,^{Footnote 26 Footnote 27} while short duration of breastfeeding has been implicated as a predisposing factor,^{Footnote 28} especially in children at increased genetic risk.^{Footnote 29}
• It is hypothesized that obesity may promote the development of insulin resistance, which in turn results in the autoimmune destruction of beta-cells trying to compensate for the insulin imbalance.^{Footnote 30 Footnote 31}

Short- and long-term complications of type 1 diabetes

The long-term complications of type 1 diabetes^{Footnote 32} are the same as those for type 2 diabetes, including cardiovascular disease, retinopathy, and nephropathy (Chapter 2). However, because type 1 diabetes is most commonly diagnosed in childhood, there is an increased risk of long-term complications at earlier ages compared to individuals living with type 2 diabetes. In addition to the long-term complications of diabetes, people with type 1 diabetes are at greater risk of immediate and acute complications because of their reliance on an external source of insulin. The administration of too much or too little insulin, resulting in extremes in glycemic levels, can lead to life-threatening complications caused by hypoglycemia and DKA.

Hypoglycemia occurs when excess insulin in the blood leads to extremely low glycemic levels. In addition to insulin dosage errors or incorrect estimations, common causes include missed meals, illness, and increased physical activity without a corresponding reduction in insulin or increase in carbohydrate consumption.^{Footnote 33} Episodes of severe or recurrent hypoglycemia, especially before the age of five years, may affect cognitive functions and result in learning problems.^{Footnote 34 Footnote 35} Severe hypoglycemic episodes have been shown to affect performance and verbal IQ in children with type 1 diabetes.^{Footnote 36 Footnote 37} DKA, often referred to as diabetic coma, results from hyperglycemia due to a lack of insulin. It is the leading cause of death and permanent disability among children with diabetes.^{Footnote 38} DKA is a preventable complication that occurs at the onset of 15% to 67% of type 1 diabetes cases.^{Footnote 39 Footnote 41} Among children with established type 1 diabetes, most DKA episodes are associated with insulin omission or treatment error.^{Footnote 42 Footnote 43}

More frequent emergency department admissions and hospitalizations,^{Footnote 44} decreased quality of life and increased mental health issues such as depression, anxiety and eating disorders,^{Footnote 45} are also more common among children with type 1 diabetes. Fortunately, treatment can prevent acute complications and reduce the development of long-term complications.^{Footnote 46}

Management strategies for children and youth with type 1 diabetes

Intensive daily management of glycemic levels is essential for reducing short- and long-term complications of type 1 diabetes.^{Footnote 47 Footnote 49} In contrast to the fixed glycemic targets provided for adults, targets for children vary by age.^{Footnote 50}

Meticulous balancing of diet and physical activity with insulin intake is the core of type 1 diabetes management. In Canada, two strategies for administering insulin that are commonly used to manage type 1 diabetes are multiple daily injections (MDI) of insulin using syringes or pen devices, and continuous subcutaneous insulin infusion (CSII) from an insulin pump. An insulin pump, which is a programmable medical device worn outside the body, aims to mimic the natural insulin delivery of the pancreas. It continuously infuses insulin based on the individual's body needs over the course of a 24-hour cycle. Studies have shown that CSII reduces HbA1c levels significantly more than MDI, and that CSII reduces rates of severe hypoglycemia and contributes to a greater quality of life for patients.^{Footnote 51} Optimal management of diabetes implies that the most adequate tools and technologies for each patient should be made available and accessible to those who need it.

Several novel therapies are currently being tested as cures for type 1 diabetes, including pancreatic islet transplantation and the development of an artificial pancreas.^{Footnote 52} Pancreatic islet transplantation was previously limited by the lack of donors and immune rejection of graft, but cell replacement therapy now holds substantial promise with the use of stem cells.^{Footnote 53} Developments in pump therapy with the use of continuous glucose monitoring have advanced diabetes care, and an artificial pancreas could be produced in the foreseeable future.^{Footnote 54 Footnote 55}

Challenges in management

Children and youth with type 1 diabetes face many of the same challenges in managing their disease as do adults, but face additional issues specific to their age.

Developmental stages of childhood

The physiological, psychological, social and emotional changes that occur as a child ages can be challenging for the management of type 1 diabetes. As a child grows, insulin requirements change and management strategies must be adapted accordingly. During the earlier stages of a child's growth and development, parents inevitably have more responsibility for the management of glycemic levels. As children mature, they become more capable of taking on these responsibilities.^{Footnote 56 Footnote 58}

Adolescence can be a particularly difficult time for management of glycemic levels as adolescents take on responsibility for the management of their disease at the same time as hormonal changes affect glycemic levels and impact insulin requirements.^{Footnote 34 Footnote 35 Footnote 50} Body weight issues and eating disorders, more frequent among adolescent females than males, may incite some adolescents to adopt practices that are detrimental to the management of glycemic levels, such as omitting or modifying insulin doses as a means to control their weight.^{Footnote 45 Footnote 59}

The stress of caring for a child with type 1 diabetes can also strain the health of a parent.^{Footnote 56 Footnote 57} Parents or guardians of children with type 1 diabetes live with the daily demands of round-the-clock monitoring of glycemic levels in their child. Daily activities include administering insulin injections, managing diets and monitoring physical activity levels.

Care in schools

Because children and youth spend a great deal of their daytime hours in school, this setting must meet the needs of children and youth with type 1 diabetes.^{Footnote 60 Footnote 65} Levels of support and care adjusted to the age and development of a child are essential for the proper management of type 1 diabetes in the school setting. In Quebec for example, guidelines on interventions in school settings for children living with type 1 diabetes have recently been published. This protocol describes the role and responsibilities of the different personnel involved, including parents, school nurses, the school principal and other educators in charge of the children, as well as the children themselves.^{Footnote 66} Nurses, teachers and other personnel who are trained to help monitor and support the needs of children with type 1 diabetes can make a significant difference in the quality of a child's diabetes management and in ensuring that the child's health and performance in school are not compromised. While preventive measures are paramount, access to Glucagon is essential when a severe hypoglycaemic event occurs. Glucagon is not yet universally available in schools across Canada.

Type 2 diabetes

Historically, type 2 diabetes was viewed as an adult-onset disease, and all cases of diabetes in young people were assumed to be of type 1. Although still not common among children and youth, type 2 diabetes is now known to occur in this group, typically developing during or just after puberty, between the ages of ten and 19 years.^{Footnote 5} The development of type 2 diabetes in children and youth is not well understood. The progression from impaired glucose tolerance to type 2 diabetes is faster in children than in adults.^{Footnote 67 Footnote 68} Also, acute complications, such as DKA, most commonly associated with type 1 diabetes, appear to be more common in newly diagnosed children and youth with type 2 diabetes than among adults.^{Footnote 69} Contrary to the gender pattern observed in the adult population, type 2 diabetes seems more frequent among female children and youth than their male counterparts.^{Footnote 70}

In the last two decades, type 2 diabetes has been on the rise among children and youth globally.^{Footnote 71} Type 2 diabetes in children was first brought to the attention of the scientific community in Canada when a description of 12 Aboriginal children in Manitoba with type 2 diabetes was published in 1992.^{Footnote 72} Since then, several studies in Canada^{Footnote 70 Footnote 73 Footnote 74} and internationally^{Footnote 5 Footnote 13 Footnote 75} have reported increases in type 2 diabetes in children and youth. In the United States, the incidence of type 2 diabetes is 8.1 cases per 100,000 person-years in children aged ten to 14 years, and 11.8 cases per 100,000 person-years in those aged 15 to 19 years.^{Footnote 5} In the United Kingdom, the incidence of type 2 diabetes in children less than 17 years of age was at least 0.53 cases per 100,000 children per year.^{Footnote 75}

In Canada, trends in type 2 diabetes in children and youth have been reported for specific populations and provinces. In 2004, Manitoba reported 35 to 40 new cases of childhood type 2 diabetes, representing about 30% of all new cases of childhood diabetes in Manitoba annually.^{Footnote 76} Between 2000 and 2002, the Diabetes Care Program of Nova Scotia reported 5.4 new cases of type 2 diabetes per 100,000 children under the age of 19 years. A higher proportion of 10.5 new cases per 100,000 children was reported in children between the ages of ten and 19 years.^{Footnote 77} A Canada-wide population-based surveillance study of new onset childhood type 2 diabetes was conducted from 2006 to 2008.^{Footnote 69} In this study, 227 cases of type 2 diabetes were identified in a two-year period, which was extrapolated to a minimum national incidence rate of 1.54 new cases per 100,000 children under the age of 18 years. In turn, this incidence rate would translate into at least 113 new cases of childhood type 2 diabetes diagnosed in Canada every year. This study found differences in prevalence across Canada, which likely reflect differences in the proportions of children of First Nations or certain ethnic descent who are at higher risk of developing type 2 diabetes. The incidence of children and youth aged 18 and under with type 2 diabetes was higher among Aboriginal children and youth than among Asian, African and Caribbean, and Caucasian children and youth. Similar results were reported in international studies.^{Footnote 5 Footnote 78} An earlier retrospective study conducted in the Toronto area also showed an overrepresentation of Asian and African children with type 2 diabetes.^{Footnote 70}

Risk factors for type 2 diabetes

The factors that increase the probability that a child will develop type 2 diabetes are the same risk factors seen in adults (Chapter 4). They include overweight and obesity, physical inactivity, a family history of diabetes, certain ethnicities, maternal gestational diabetes and insulin resistance.

Obesity

A recent Canadian surveillance study found that 95% of children newly diagnosed with type 2 diabetes were obese.^{Footnote 69} Overall, in the last 25 years, rates of obesity in children and youth have been increasing rapidly throughout the world. In Canada, the number of obese children aged two to 17 years more than doubled, from 3% in 1978-1979 to 8% in 2004.^{Footnote 79} The emergence of type 2 diabetes in children and youth has occurred concurrently with the rise in rates of childhood obesity.

Family history

Children and youth with a family history of type 2 diabetes show reductions in insulin sensitivity at a younger age than children with no family history.^{Footnote 80} Studies show that more than 75% of children and youth with type 2 diabetes have at least one relative with the disease.^{Footnote 81} In Canada, more than 90% of children and youth with type 2 diabetes have a first or a second degree family member with the disease.^{Footnote 69 Footnote 70}

Ethnicity

Children from some ethnic groups (First Nations, African/Caribbean, Hispanic, and South Asian) are at higher risk of earlier onset of type 2 diabetes.^{Footnote 13 Footnote 72} A majority of Canadian children with type 2 diabetes (75%) belong to a high-risk ethnic group.^{Footnote 69}

Puberty

Individuals aged 13 to 17 going through puberty may be more vulnerable to the development of type 2 diabetes.^{Footnote 69 Footnote 75} Among Canadians under age 18, type 2 diabetes developed at an average age of 13.7 years, with only 8% of children developing it before ten years of age.^{Footnote 69}

Short- and long-term complications of type 2 diabetes

Studies show that diabetes-related complications develop more rapidly in children and youth with type 2 diabetes than in adults.^{Footnote 82 Footnote 85} Complications also appear to develop earlier in children and youth with type 2 diabetes than in those with type 1 diabetes.^{Footnote 86 Footnote 87}

Typically, children and adolescents with type 2 diabetes face complications from both diabetes and obesity. They have been shown to have an early and increased risk of cardiovascular disease and its risk factors.^{Footnote 88} One study found that hypertension was up to eight times more common in youth with type 2 diabetes than in those with type 1.^{Footnote 89} In a study of children from the United States with type 2 diabetes, between 18% and 61% had hypercholesterolemia, and between 10% and 32% had hypertension. In a recent study of Canadian children with type 2 diabetes, 45% had dyslipidemia and 28% had hypertension at diagnosis. In addition, 37% of children and youth with a new diagnosis of type 2 diabetes already had at least one co-morbid condition related to their diabetes or obesity, at an average age of 13.7 years.^{Footnote 69}

The development of type 2 diabetes early in life inevitably leads to increased costs to the health care system, as diabetes management and the treatment of its complications require lifelong attention.

Management strategies for children and youth with type 2 diabetes

Lifestyle change is the cornerstone of type 2 diabetes management in children and youth, although medication is sometimes necessary. Children and youth with type 2 diabetes are optimally managed when an interdisciplinary health care team helps the achievement of treatment goals.^{Footnote 50} Education of the patient should be age-appropriate and culturally sensitive, and should focus on the lifestyle and health behaviours of the whole family.

A critical component in the management of type 2 diabetes is screening for, and prevention of, complications. The Canadian Diabetes Association clinical practice guidelines recommend that children and youth with type 2 diabetes be screened for hypertension at every clinical visit, and that they be screened for other risk factors for type 2 diabetes including hypercholesterolemia, non-alcoholic fatty liver disease, nephropathy and retinopathy when they are first diagnosed and annually thereafter.^{Footnote 50}

In Canada, insulin and metformin (an oral medication) are the only medications approved for use with children and youth with type 2 diabetes.^{Footnote 90} There is limited information on the effectiveness and safety of other oral hypoglycemic medications in children and youth with type 2 diabetes. Children and youth who have high glycemic levels that result in a diabetic coma or persistent hyperglycemia are often placed on insulin therapy.^{Footnote 91}

Limitations of diabetes surveillance in children and youth

With both types of diabetes on the rise, a global effort is underway to conduct population studies to determine the incidence and prevalence of type 1 and type 2 diabetes in children and youth. At this time, there is limited population-based data in Canada to document the trends in childhood diabetes or the demographic, behavioural, clinical and socioeconomic characteristics of this population. Studies that do exist tend to focus on specific subgroups and are not population-based.

Clinically, it may be difficult to distinguish between type 1 and type 2 diabetes. Since type 1 diabetes remains the predominant form in children and youth, cases of type 2 diabetes are sometimes misclassified. This means there may be a substantial number of children and youth whose type 2 diabetes has remained undiagnosed, or who have been misdiagnosed with type 1 diabetes. Currently, the CCDSS does not distinguish between type 1 and type 2 diabetes. However, studies are underway to expand CCDSS methodology for this purpose. For example, a study in British Columbia has been successful in differentiating type 1 and type 2 diabetes within administrative data in persons aged less than 19 years by adapting CCDSS methodology through the application of algorithms that use demographic and drug treatment data.^{Footnote 92}

Looking ahead

Effective national surveillance is vital in order to gain a better understanding of the magnitude, characteristics and public health consequences of type 1 and type 2 diabetes in Canadian children and youth. Type 1 diabetes is not yet preventable. However, healthy weight and regular physical activity remain key to the reduction of type 2 diabetes in this population and contribute directly to the optimal management of both types of diabetes. Since children and youth diagnosed with type 1 and type 2 diabetes will live with the disease for life, effective management is a critical step toward reducing their risk of complications and improving their quality of life.

In that regard, the endorsement of the Curbing Childhood Obesity: A Federal, Provincial and Territorial Framework for Action to Promote Healthy Weights by federal, provincial and territorial Ministers of Health in 2010 signalled a commitment from these governments to work together, with partners across and outside the health sector, to take action on promoting healthy weights among children. This framework is comprised of three key strategies: "making childhood overweight and obesity a collective priority for action"; "coordinating efforts on three key policy priorities" (supportive environments, early action and nutritious foods); and "measuring and reporting on collective progress". Currently, actions are being undertaken as part of each strategy by the Ministers of Health, their governments and other sectors, to address childhood obesity and promote healthy weights.

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