Athough the incidence of type 2 diabetes mellitus (type 2 DM) in chidren and adolescents has increased in recent years, type 1 diabetes mellitus (type 1 DM) is the most prevalent type seen in this age group and is reviewed in more detail here. Within the context of sport participation, most patients seen by pediatricians are adolescents and although the following discussion mostly refers to adolescents, it is equally applicable to children unless otherwise specified.

Definitions

The diagnostic criteria for diabetes mellitus are shown in Table 15-1.

Epidemiology

There are 20.8 million individuals in the United States with diabetes mellitus, comprising 7% of the total population; 176,500 of them are children and adolescents younger than 20 years of age. One in 400 to 600 children and adolescents have insulin-dependent diabetes, also called type 1 DM.1

Pathogenesis

A brief summary of the pathophysiology of diabetes mellitus as it relates to sports participation is essential to better understand the principles of management of diabetes in children and adolescents.

The availability of carbohydrates is important for use by the exercising muscles. Nondiabetic children and adolescents have full muscle and liver glycogen stores at rest. During exercise, muscle glycogen is used first to release lactic acid for the Cori cycle, followed quickly by liver glycogenolysis. As insulin levels decrease, liver glycogenolysis is continued; at the same time, with increased blood flow, binding of insulin to receptors in skeletal muscles is increased causing increased glucose uptake and metabolism during exercise. The glycogen stores in muscles and liver are then replenished from blood glucose following completion of physical activity.2–4

It is believed that hepatic glucose production is the same in children and adolescents with diabetes and those without diabetes. However, there are some basic metabolic differences in carbohydrate metabolism between children and adolescents with and without diabetes.2 Compared with children and adolescents without diabetes, in children and adolescents with diabetes:

• Gluconeogenesis may be increased up to three times the normal
  
• There is reduced mitochondrial pyruvate dehydrogenase activity, which may lead to compromised glucose oxidation in muscles, and
  
• Relatively higher fatty acid oxidation occurs in the exercising muscles.

The effects of exercise will vary in the adolescent with diabetes depending on the level of the metabolic control and the amount of insulin available in the body. It has also been shown that the adolescent with diabetes will have a consistent response to similar level of exercise activity, metabolic control and insulin dosing.

Insulin may be more rapidly absorbed if administered in the exercising limb. If there is excessive insulin available, muscle and liver glycogenolysis is suppressed, compromising the availability of glucose, whereas the glucose requirement in the exercising muscle is increased. This leads to hypoglycemia, which can occur during the activity, soon after the activity, or hours later.3

There is no significant change in the “counter-regulatory” hormone response to physical activity in adolescents with well-controlled diabetes compared with adolescents without diabetes. In hypoinsulinemic states, the response of the counter-regulatory hormones is exaggerated with an abnormal increase in glucagon, cortisol, growth hormone and catecholamines, which may lead to worsening of hyperglycemia, lipolysis, and ketosis. In scenarios of under-insulinization, hepatic glycogenolysis is promoted while glucose utilization in the muscle may be decreased, again causing hyperglycemia.3 Ketogenesis is also promoted by stimulation of lipolysis as result of escape from insulin inhibition by hormone sensitive lipase.2,5

Clinical Presentation

Within the context of sports participation, the previously undiagnosed adolescent may first present with symptoms of diabetes mellitus. On the other hand, and least commonly, the adolescent with type 1 DM may present with symptoms and signs of macro- and microvascular complications. Most commonly though, the adolescent with type 1 DM who is participating in sports is likely to be seen for symptoms and signs of either hypoglycemia or hyperglycemia with or without ketoacidosis. Additionally, adolescents who are deficient in insulin may develop postexercise hyperglycemia that may persist for several hours. A state of ketosis may develop quite rapidly in this scenario, leading to diabetic ketoacidosis and that may necessitate hospitalization. The symptoms and signs of hypoglycemia and hyperglycemia are listed in Table 15-2.

Diagnosis

Adolescents with diabetes should have the same comprehensive sports preparticipation evaluation as do adolescents without diabetes. The history should ascertain associated chronic illness, factors that may limit the ability to exercise, general well-being and overall health. Physical examination should ascertain any physical limitations or disabilities (congenital or acquired), cardiovascular or respiratory limitations, limitations of range of limb mobility and control, and deficits in central or peripheral neurological function that would cause difficulties during participation in sports. Adolescents with diabetes mellitus should have additional screening for any evidence of micro- or macrovascular complications that may predispose them to injury and compromise safety, or exacerbate the underlying disease.

Physical examination should include vital signs, careful blood pressure measurements to look for hypertension as well as orthostatic changes. A detailed neurological examination should be done to detect peripheral or autonomic neurological deficits. An yearly detailed retinal examination should be done by an ophthalmologist to identify early diabetic retinopathy. Microvascular complications are not commonly seen in adolescents prior to 10 or more years’ duration of diabetes. The incidence of micro- as well as macrovascular complications in adolescents is not very high, but adolescents who were diagnosed in early childhood may have already had 10 years’ duration of the disease and may have evidence of these complications.6

Laboratory Tests

For all adolescents with type 1 DM after 5 years’ duration and type 2 DM at the time of diagnosis, laboratory tests should include HgbA1c; urine analysis for protein, glucose and ketones; and urine for microalbuminuria (spot) in adolescents with proteinuria on urine dipstick. Annual thyroid function tests, lipid profile and antiendomysial antibodies should be performed for screening and early detection of hypo-/hyperthyroidism, hyper-/dyslipidemias and celiac disease, all of which are seen with increased incidence in Type 1 DM.7

Management

The management of type 1 DM for the adolescent must be individualized, with appropriate consultations (Box 15-1), to allow for safe participation and optimal performance in sports. Factors that determine recommendations for diabetes management during sports participation are presented in Table 15-3.8

Preparticipation Management

Preparticipation assessment of the diabetes treatment regimen is outlined in Table 15-4.9 Every athlete requires an individualized plan of care. Safe participation in sport at any level is possible with adequate self-monitoring of blood glucose (SMBG) in order to make suitable adjustments to the therapeutic regimen, including insulin dosing and modification of carbohydrate intake. Adolescents (and primary care takers of young children) need education about appropriate modifications in the insulin and diet regimens based on SMBG to avoid immediate, as well as, delayed hypoglycemia and hyperglycemia.

Baseline Metabolic Control

Sports participation may need to be delayed until satisfactory glycemic control has been achieved based on SMBG and HgbA1c levels. Factors determining the metabolic response to exercise are listed in Table 15-5. Failure to do so may result in frequent episodes of hypoglycemia and/or hyperglycemia with or without ketosis. However, a balanced approach is needed because requiring “perfect” control before allowing participation may frustrate the athlete and result in a missed opportunity to engage in a healthy and fun activity.

Hypoglycemia

Exercise-induced hypoglycemia may occur during, soon after, or over the subsequent 6 to 24 hours following the cessation of exercise.8,10 Appropriate modifications should be made in insulin dosing and carbohydrate intake, along with more frequent monitoring of blood glucose levels, to avoid hypoglycemia. The Diabetes Research in Children Network (DirecNet) Study Group demonstrated the need for modification of insulin regimen to prevent hypoglycemia following afternoon exercise.11 In addition to the hypoglycemia caused by exercise, other causes of hypoglycemia in adolescents with type 1 DM include accelerated absorption of rapid-acting insulin from an exercising limb within 1 to 2 hours of injection, blunting of glucagon response to hypoglycemia as may be seen in type 1 diabetes of more than 5 years duration, and blunting of epinephrine response to exercise seen in some adolescents with tightly controlled type 1 DM.

Hyperglycemia

Hyperglycemia may result from the effects of increased counter-regulatory hormone response especially in conjunction with a state of relative hypoinsulinemia. The question in sports and exercise settings is whether this hyperglycemia should be treated with supplemental insulin. If insulin is used, postexercise hypoglycemia may be precipitated; therefore, a smaller or lower correction factor should be used if at all, and blood glucose measurements should be followed over subsequent few hours.

Attempting to keep preexercise blood glucose levels at elevated levels to compensate for exercise-related hypoglycemia may be counter productive by precipitating ketosis. Symptoms suggestive of hypoglycemia should always be validated by blood glucose testing as symptoms of precontest anxiety may mimic symptoms of hypoglycemia, and if carbohydrates are present hyperglycemia and ketosis may occur.

Blood Glucose Assessment

Blood glucose should be assessed prior to the start of exercise or sports session. Many blood glucose testing devices with varied technological features are available (Figure 15-1). A pre-exercise snack may need to be taken based on this blood glucose value (Table 15-6).5 Blood glucose testing should be done at intervals during the sports session, especially if the session is prolonged or if symptoms of hypoglycemia occur. This should be followed by blood glucose checks after activity, as well as, for several hours after completion of the session. Overnight (2 am) blood glucose checks may be needed to detect nocturnal hypoglycemia. The American Diabetes Association (ADA) general safety guidelines for regulating glycemic response to physical activity are summarized in Table 15-7.12