Objective. To review the magnitude, characteristics, and public health importance of type 2 diabetes in North American youth.
Methods. One hundred eighty-two publications on type 2 diabetes in youth published between January 1996 and June 1999 were reviewed by the Division of Diabetes Translation at the Centers for Disease Control and Prevention, the Sansum Medical Research Institute, and the Indian Health Service.
Results. Records of 578 youth diagnosed with type 2 diabetes were reviewed from the available studies. Ninety-four percent of the children and adolescents were from minority communities, and minorities with type 2 diabetes were overrepresented relative to their population size. The mean age of diagnosis ranged from 12 to 14 years except among Pima Indians, for whom the mean age was 16 years. Patients were more likely to be girls than boys. Obesity, family history of diabetes, and acanthosis nigricans were common among this population.
Conclusions. Type 2 diabetes has been an important problem among African Americans, Native Americans, and some ethnic minorities and is now emerging in all populations. Type 2 diabetes among youth is an emerging public health problem.
The Tip of the Diabetes Iceberg
This study points out the epidemiology and characteristics of type 2 diabetes among children and adolescents in this country. It also suggests the need for further epidemiological study, particularly of the nonminority population for which data on the prevalence of type 2 diabetes among children and adolescents are more scarce.
Unfortunately, this study likely underreports the diagnosis of type 2 diabetes among private practice settings because the studies it reviewed were typically from minority health services and large medical centers rather than from communities of patients receiving their care from pediatricians and pediatric endocrinologists in private practice.
My, How We Have Grown
Type 2 diabetes was once considered a disease of adults. However, since 1980, its prevalence in childhood has increased dramatically. This increase has been best described among minority populations, with the first reports emerging from the Pima Indians. As the prevalence of obesity among children and adolescents has doubled over the past decade, this increase has paralleled the increasing prevalence of diabetes among children and adolescents.1–3 The prevalence of type 2 diabetes in children and adolescents is now as high as that of type 1 diabetes.
Obesity now affects more than one-third of all adults in the United States.4,5 It is also the most prevalent nutritional disease among youth, with 27% of children and 21% of adolescents currently considered obese. This represents a doubling in the rate of obesity among children over the past two decades.4–6
Each day in the United States, more than 2,000 people are diagnosed with diabetes, and that number is expected to nearly double by 2025, when more than 22 million Americans will have the disease. Yet even these harsh estimates may not reflect the growing epidemic of diabetes among youth.7
Presenting Symptoms Among Children and Adolescents With Type 2 Diabetes
The review by Fagot-Campagna and associates found that among children, type 2 diabetes most commonly presents itself during puberty, with 85% of the children diagnosed being overweight. A family history of diabetes has been reported to be present in 45–80% of cases. In contrast to children with type 1 diabetes who most often present with symptoms of polyuria, polydipsia, and ketonemia, only one-third of children diagnosed with type 2 diabetes have ketonuria, and most often symptoms are clinically absent.
Most children and adolescents reviewed were diagnosed because of acute symptomatology rather than because of the presence of glucosuria on physical examination. Vaginal moniliasis was the chief complaint in one study and was reported in 24% of the girls. Weight loss, ketosis, and ketoacidosis were also reported. At diagnosis, insulin and C-peptide levels were generally elevated, and islet cell antibodies were absent.
HbA1c levels were typically in the 10–13% range at diagnosis in most populations other than the Pima Indians, whose values were lower at diagnosis. Thirty-two percent of the youths reviewed had hypertension, and 8% had depression or an eating disorder.
Is It Type 1 or Type 2?
Diabetes in children is routinely assumed to be type 1 diabetes of autoimmune origin, which results in destruction of the insulin secretory ability of the islet cells and insulin dependence. Yet type 2 diabetes was first described among Pima Indian children nearly two decades ago. In recent years, numerous reports have described type 2 diabetes occurring in African-American, Hispanic, and white children. Risk factors for type 2 diabetes in children are similar to those of adults and include obesity, ethnic background, family history of diabetes, and maternal history of gestational diabetes.8
Interestingly, this review reported that while diabetic ketoacidosis may be present in as many as 25% of African-American adolescents presenting with diabetes, the course of the disease may ultimately follow that of type 2, rather than type 1, diabetes.9 Islet cell and other specific antibodies directed toward the b-cell are almost always negative at the time of initial presentation. Although initially treated with insulin, many African-American adolescents with diabetes may ultimately require no medical therapy.
Despite the age of onset and overlapping symptoms of type 1 diabetes, initial insulin treatment has often led to misclassification among children and adolescents.
Medical nutrition therapy continues to be the mainstay of treatment and is the best and safest measure for the prevention and treatment of diabetes.
Insulin is currently the only FDA-approved treatment for adolescents and children with diabetes. A clinical study of 130 pediatric practices demonstrated that 46% of children treated with oral agents were prescribed sulfonylureas.1 Another multicenter trial among 82 children found that metformin was effective in lowering HbA1c concentration without a significant increase in adverse events. The main disadvantage of insulin is its potential to cause hypoglycemia.10
Fagot-Campagna and associates found only five prospective follow-up studies evaluating children with type 2 diabetes after their diagnosis. In general, poor glucose control was reflected by an average HbA1c >10% at follow-up 6 months to 10 years after diagnosis. In one study of Pima Indians in which subjects had a median age of 26 years at follow-up, microalbuminuria was present in 58%, hypertension in 14%, hypercholesterolemia with total cholesterol values >200 mg/dl in 30%, and hypertriglyceridemia >200 mg/dl in 55%.
What’s Television Got to Do With Diabetes?
The average American home now has 2.5 television sets compared with 2.25 sets 4 years ago. At the end of life, the average American will have spent 11 years watching television.11 American children begin watching television at a very early age, sometimes as early as 6 months of age, and are regular viewers by age 2.11 American children watch television for an average of 4 h a day, 28 h a week, and 2,400 h a year—nearly 18,000 h by the time they graduate from high school.12
A Harvard University study has linked watching too much television with type 2 diabetes. The study found that men who spent 40 h a week watching television were more than twice as likely to get diabetes than those who watched for <2 h a week. The investigators concluded that there is a strong and highly significant connection between television viewing and the risk of developing type 2 diabetes.13
When television viewing and body fat were compared, children who watched 4 h or more of television per day had a higher body fat and greater body mass index than those who watched <2 h per day. The investigators also found that the average adult male watches 29 h of television per week, and men with the lowest total physical activity scores were more than twice as likely to be obese as those who watched the least television.
Another randomized, controlled, school-based trial was designed to study the effects of reducing television viewing on changes in adiposity, physical activity, and dietary intake. Reduced television viewing and decreased measures of adiposity were seen in children participating in the trial. Reducing television viewing is a promising approach to help prevent obesity in children.14,15
Is Education Hurting Our Children?
The past decade has brought a decreased emphasis on good nutrition in our schools, and in some cases even blatant promotion of poor nutritional choices.
Many high-school graduates do not know how to read food labels. More than 84% of children get more than the recommended 30% of daily calories from fat, and 90% exceed the recommendation for 10% of daily calories from saturated fat.16 Fewer than 5% of teens eat the recommended five daily servings of fruits and vegetables.17
A survey conducted in California public high schools18 found that >85% of the school districts responding sold fast-food items. Pizza, hamburgers, submarine sandwiches, french fries, chips, cookies, yogurt, bagels, ice cream, and sodas accounted for up to 70% of all food sales in high schools. Brand-name fast-food products proliferated; more than half of the schools surveyed carried Taco Bell, Subway, Dominos, Pizza Hut, or other branded fast foods.
At least 72% of the responding districts allowed fast-food and beverage advertising, such as posters, scoreboard advertising, and other signage, on their campuses. Twenty-four percent of the districts that allowed advertising had contracted promotional rights to a fast-food or beverage company in exchange for cash or equipment. In addition to these financial arrangements, some food service directors characterized fast-food sales as a tactic for keeping their student customers eating at the schools.
During the past several decades, we have rapidly grown in the areas of communication, technology, science, and medicine. So, too, have we grown as individuals in our size and weight.
Less than a century ago, there were no airplanes, no cars, and no fast-food restaurants. Not surprisingly, this phenomenal technological growth has come at a price—an expanded girth that has extended not only to adults, but also to children. This has resulted in a 70% rise in diabetes among 30- to 40-year-olds and a doubling in the number of children with type 2 diabetes in less than a decade.7
The future morbidity of type 2 diabetes in children and adolescents, similar to that of diabetes in adults, will result from complications. Type 1 diabetes ranks among the leading chronic childhood diseases in terms of limitation of usual activity, school absences, hospitalizations, and medical contacts. However, the longer duration of disease resulting from the development of type 2 diabetes in the first or second decade of life may well be associated with long-term complications, as well as the comorbidities of hypertension, hyperlipidemia, and cardiovascular disease due to the longer exposure to hyperglycemia.
Ironically, there are 58 million overweight Americans in the United States—a number almost identical to that of Americans who eat at one of the 160,000 fast-food restaurants in the United States each day.19 As we look to the future of type 2 diabetes in children, we must look at ourselves in the mirror. As physicians, health care providers, and parents, we must begin to walk the walk of the talk we talk. Daily exercise must become a part of everyone’s life. Attention to the foods we eat, combined with less attention to television, is critical if we are to roll back the hands of time that have placed us in our seat more than on our feet.
As I was writing this review, I heard on the radio that by the time most American children begin the first grade, they will have spent the equivalent of 3 school years in front of the television, with preschoolers watching from 13.3 to 27.8 h of television per week. Those children watching television are at higher risk for the development of diabetes, and that is not aided by the fact that advertising for fast food now often specifically targets children. Parking not only ourselves, but also our children, in front of the television is hazardous to our health and may even negatively affect our food choices.
Claresa Levetan, MD, is director of diabetes education at MedStar Research Institute in Washington, D.C. She is an associate editor of Clinical Diabetes.