Susan Phillips, MD
TCOYD Newsletter, Vol. 22, 2007

Part I: On The Rise In The Very Young

Type 1 diabetes is the most common form of diabetes affecting children and constitutes approximately 1% of all diagnosed cases of diabetes in the United States. Recent data on the worldwide incidence of T1DM reveals a shift in its incidence rates among very young children.

The increasing number of infants and toddlers with diabetes presents a unique set of challenges to both the diabetes management team and to families. This age group requires specialized insulin regimens, meal planning and monitoring to promote normal growth and development, and reduce the risk of both short-term and long-term complications.

Type 1 diabetes mellitus, or T1DM, is a heterogenous condition characterized by absolute insulin deficiency. The criteria for the diagnosis of diabetes in the child is the same as in the adult, and may be made based on the presence of classic symptoms of increased thirst, urination, and unexplained weight loss in association with a random blood glucose >200mg/dl or a fasting (>8 hrs) blood sugar of ³126, or a 2h post meal glucose > 200 mg/dl during an oral glucose tolerance test. There are a number of causes of T1DM; however, the most common cause is autoimmunity, a condition that results when the immune system mistakenly identifies insulin producing cells as foreign bodies and targets them for destruction. Symptoms of diabetes do not usually manifest until over 90% of the beta cell insulin secretory capacity is lost.

Type 1 Around the World

The global incidence of T1DM is highly variable. Between 1990 and 1994 the World Health Organization initiated The Multinational Project for Childhood Diabetes study to monitor the patterns of incidence of T1DM. During the study 4.5% of the world’s population 14 years or younger were surveyed, and nearly 20,000 cases of T1DM were identified from the 75 million sample population. Among the 100 populations studied the incidence of T1DM varied over 350-fold, with the lowest rates of 0.1/100,000 in China and Venezuela to the highest rates of 36.8/100,000 in Sardinia and 36.5/100,000 in Finland. Interestingly many studies report incidence rates that are lower during the warmest periods of the year and an increasing number of reports suggest lower incidence rates of T1DM in populations closest to the equator.

In the United States the incidence rate of T1DM ranges between 15- 17/100,000, while the prevalence rate or the number of children with T1DM at a given time, is approximately 1/500. In the United States, as in many other parts of the world, the incidence of T1DM has been on the increase and appears to be occurring more frequently in children under the age of 5. In Great Britain for example an analysis of children with T1DM in 1988 showed 26% were under the age of 5 years versus 19% for the each of 1974 and 1973. In the Swedish Childhood Diabetes registry recording all incident cases of diabetes, ages 0-14 years since July 1977, there has been an increase in T1DM among children less than 10 years of age. In Germany, the incidence of T1DM in children under 5 years increased from 6.86/100,000 cases in 1993 to 9.68/100,000 in 1995. Czechoslovakia, Australia, Denmark, France, Finland, and Switzerland also report steep increases in the incidence of T1DM among the youngest age groups. In the United States 50 out of every 100,000 people diagnosed with type 1 diabetes are under age 3. While there are no clear explanations for the increased rates and earlier age of onset of T1DM, investigators believe that environmental factors rather than changes in genetic risk are to blame. This belief is supported by the fact that the increased incident rates have occurred over a brief period and in relatively stable populations making changes in the gene pool unlikely as a cause.

Why the Increase?

Various factors have been implicated to influence the incidence of T1DM. Foremost among these is genetic risk. For example, siblings of type 1 diabetic patients have a 40-fold increased risk of developing T1DM (5%). Children whose father or mother has T1DM have a 35-fold (7%) or a 10-fold (2%) higher risk respectively than the general population.1 (The lifetime risk of type 1 diabetes is ~0.7% for the general population.) However, the susceptibility of those genetically at risk appears largely dependent on environmental triggers. Of these, the early introduction of cow’s milk protein has been strongly suspected. Decreased breastfeeding during the 1950’s and 1960’s was followed by a sharp increase in T1DM incidence from the 1970’s forward. It has been postulated that the structural similarity of a major milk protein to an islet cell antigen (ICA 69) may be the basis the association. The ongoing Trial to Reduce Type 1 Diabetes Mellitus in the Genetically at Risk (TRIGR) study was designed to determine whether avoidance of cow’s milk for the first six months of life might reduce incidence of T1DM in the genetically at risk. A large number of viral agents have also been implicated in the incidence of T1DM in high-risk populations. Among them congenital rubella is the most highly related but others including coxsackie, cytomegalovirus, ECHO, mumps, and retroviruses have also been associated with the occurrence of T1DM.

Detection

The diagnosis of T1DM in very young children is frequently delayed. Often classic symptoms persist undetected because they cannot be communicated or are difficult to recognize. Repeated acute infections, which affect over 50% of the youngest children at diagnosis may also mask signs and symptoms of diabetes. Because of the delay in diagnosis only a small minority of these children present while still only hyperglycemic. The majority of children present with diabetic ketoacidosis, with some centers reporting between 53-85% of children age <2 yrs having ketoacidosis when diagnosed.

Caring for Children with Diabetes

The management of T1DM in infants and toddlers represents a complex set of problems. Optimal management of these issues requires close cooperation between the patient, family and health care team. Click here for an article exploring some of the issues related to caring for youngsters with diabetes in the next TCOYD Newsletter.

1. Lifshitz Pediatric Endocrinology Vol 1 p85 citing Karvonen, M. Diabetes Mondiale Diabetes Care 2000 23(10) 1516-1526

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