Vol. 14 •Issue 3
• Page 55
Assessing Diabetes Risk
Danger in the Family Tree
By Edwidge Jourdain Thomas, NP
Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia that results from defects in insulin secretion, insulin action or both.1 It is one of the more costly and burdensome chronic diseases of our time and is increasing rapidly.2 More than 171 million adults throughout the world now have diabetes.3,4
Although a genetic influence has been reported, experts agree that the surge in diabetes is also associated with factors that include population growth, aging, physical inactivity and obesity.5 At one time, obesity was considered a primary reason for the escalating prevalence of diabetes. National health data suggest it is not solely responsible, however. Even if the prevalence of obesity remains stable until 2030 (an unlikely scenario), the number of people with diabetes would more than double as a consequence of aging and urbanization.5
As a result of media attention on the epidemic of obesity and its role in other chronic diseases, the public has become more cognizant of risk factors. In today's medical encounters, the discussion of disease risk based on genetics and lifestyle is becoming routine. In many cases, genetic predisposition is one of many determinants of disease risk.
Diabetes Risk
Many educated and motivated people are changing their lifestyles to decrease their risk of developing type 2 diabetes. Risk factors that cannot be modified are age, ethnicity, other medical conditions and family history. Although research suggests that type 2 diabetes has numerous causes, parents with a maternal and paternal family history of diabetes may be particularly concerned for their children. Because of this strong family history of disease, are their children at greater risk for developing type l diabetes, the most devastating form?
Case Presentation
"Mrs. V" is a 32-year-old woman in good health. She has no clinical evidence of hypertension, hyperlipidemia, type 2 diabetes or obesity. She has no past medical history for chronic disease. Her past surgical history includes a bone reconstruction from a right knee fracture.
Mrs. V reports no illicit drug use and has a 3-year smoking history of 10 cigarettes a day. She quit smoking 10 years ago. Mrs. V says she drinks an average of six alcoholic drinks per month. She has a body mass index of 23 by maintaining a healthy lifestyle: a well-balanced, high-fiber diet and a daily exercise regime. Body mass index is a calculation of body weight in kilograms divided by the square of the height in meters. It is more highly correlated with body fat than other indices of height and weight.6
Mrs. V attributes her good health to her lifestyle and her commitment to modify many of the risk factors for type 2 diabetes. Her mother and father have the disease.
Mrs. V's mother was diagnosed with diabetes, hypertension, hyperlipidemia and coronary artery disease at age 40. Her conditions are well managed with diet, exercise and oral medications. Mrs. V's father was diagnosed with hypertension, diabetes and hyperlipidemia at age 35 and treats them with medications and diet. He is now 60, without any evidence of end-organ damage. Mrs. V's maternal and paternal grandparents have a history of hypertension, hyperlipidemia, type 2 diabetes and early death from coronary artery disease.
Mrs. V's siblings, nieces and nephews have no clinical evidence of diabetes or any other chronic disease at this point. Of 24 cousins and their offspring, only two men and three women have type 2 diabetes, hypertension and hyperlipidemia. The conditions are unrelated to obesity.
Mrs. V's spouse, Mr. V, is 32 with no clinical evidence of diabetes. He was diagnosed at age 25 with essential hypertension without end-organ damage. His blood pressure is well controlled with a balanced high-fiber diet, daily exercise regime and daily medication intake of a calcium channel blocker (Norvasc), folic acid and baby aspirin.
Mr. V maintains a healthy lifestyle by minimizing stress, alcohol and weight. He reports no smoking history or illicit drug use. He drinks four to six alcoholic drinks per month. His body mass index is 24, and he is in excellent medical condition.
Mr. V's father has hypertension, type 2 diabetes, hyperlipidemia and coronary artery disease with good control on oral medications and insulin at age 60. His mother has hypertension, which she controls with diet and medication, and is a 10-year survivor of uterine cancer. His brother is healthy without any chronic disease, but his sister has poorly controlled diabetes and obesity.
Several of Mr. V's cousins are obese, but he does not know whether they have been diagnosed with diabetes, hypertension, hyperlipidemia or coronary artery disease.
Mr. and Mrs. V's children, ages 1, 2 and 4, are in generally good health. The girls exhibit normal growth and cognitive and emotional development. They have all been vaccinated according to standard recommendations. Their heights and weights are proportionate to children of normal weight. They take daily vitamins, eat a well-balanced high-fiber diet, and perform age-appropriate daily exercise.
Literature Review
The most important question about type 1 diabetes remains unanswered: What causes it?6 No studies directly link type 2 diabetes with risk for type 1 diabetes, but scientists continue to pursue a possible connection. All studies of type 1 diabetes have been limited to patients who already have the disease. This research has isolated and confirmed that the main locus defining the genetic linkage of type 1 diabetes is encoded in the complex human leukocyte antigen (HLA) region on human chromosome 6.7 These genetic markers are powerful predictors of type 1 diabetes.8 Whether these studies are applicable or replicable in the general population is debatable, because 90% of patients with type 1 diabetes have no family history of diabetes.8
The genetic investigations have given a small degree of clarity to the genetic susceptibility of type 1 diabetes, and certain environmental determinants are under investigation.7 Although many studies have reported conflicting results, exposure to certain environmental factors appears to be a causative factor.8 These environmental factors include viral infections such as coxsackie B4 virus and cytomegalovirus, exposure to N-nitroso derivative, and the use of cow's milk in infancy.7
The significant body of research on the cow's milk theory has prompted an international consortium to embark on a major trial to test this hypothesis.9 The consortium, which consists of six clinical centers in Finland, Germany, Sweden and North America, is conducting The Environmental Determinants in Diabetes of the Young (TEDDY) study. The research is investigating genetic and genetic-environmental interactions that may influence the development of type 1 diabetes.
Case Analysis
Since there are no overt signs of type 1 diabetes in the V family, genetic testing outside a clinical trial is strongly discouraged. The cutoff values for some immune marker assays have not been established for the clinical setting.1 Additionally, there is no consensus about how to proceed when a positive result is obtained.1 Given that there is no proven method of preventing or delaying the onset of type 1 diabetes, it would be unethical to offer the V family genetic testing at this time.1
The V children have a higher probability of developing type 2 diabetes due to their nonmodifiable risk factors of family history and ethnicity. The best approach to delay or possibly prevent type 2 diabetes in the V girls would be to maintain a healthy lifestyle and normal weight. A number of trials have studied the various modalities to prevent or delay type 2 diabetes. The most well-known trial showed that lifestyle interventions can prevent or delay type 2 diabetes in 58% of patients.10
Putting It Into Practice
While scientists continue to study the causes of type 1 diabetes, it is our responsibility to assess risk and advise patients to change modifiable risk factors for type 2 diabetes. These include weight management and avoidance of cigarettes and excess alcohol intake. As experts in health education as well as clinical care, NPs are ideally suited to counsel parents about reducing diabetes risk in their children.
References
1. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care. 2003;26:S5-S20.
2. American Diabetes Association & the National Institute of Diabetes and Digestive and Kidney Diseases. Prevention or delay of type 2 diabetes. Diabetes Care. 2004;27:S47.
3. Wild S, et al. Global prevalence of diabetes. Diabetes Care. 2004;27:1047-1053.
4. King H, et al. Global burden of diabetes, 1995-2025: prevalence, numerical estimates and projections. Diabetes Care. 1998;21:1414-1431.
5. Bray GA, et al. Handbook of Obesity. New York: Marcel Dekker Inc.; 1997:32.
6. Atkinson M, Gale E. Infant diets and type 1 diabetes: too early, too late, or just too complicated. JAMA. 2003;290(13):1771.
7. Zalloua PA, et al. Type 2 diabetes family history delays the onset of type 1 diabetes. J Clin Endocrin Metab. 2002;87(7):3192-3196.
8. Ronbloom AL, et al. Therapeutic controversy: prevention and treatment of diabetes in children. J Clin Endocrin Metab. 2000;85(2):494-506.
9. National Institutes of Health Consortium for Identification of the Environmental Determinants of Diabetes in the Young (TEDDY). Available at: http://www.teddystudy.org. Accessed Jan. 10, 2006.
10. Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle interventions and metformin. N Engl J Med. 2002;346(6):393-403.
Edwidge Jourdain Thomas is an adult nurse practitioner with a doctorate degree in nursing practice. She practices with Columbia Advanced Practice Nurse Associates in New York, N.Y., and is an assistant professor of clinical nursing at Columbia University School of Nursing, also in New York.
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