Diabetes Mellitus
Disease Management
DIAGNOSTIC CRITERIA
The diagnosis of diabetes is based on several findings. The following criteria have been established by the American Diabetes Association (ADA)1:
LIFESTYLE TREATMENT
Medical Nutrition Treatment
Guidelines for medical nutrition therapy2–7 have been established by the ADA and are summarized in Box 1. The primary focus of these guidelines is targeted to outcomes including glycemic control, weight reduction (as appropriate), blood pressure control, and a favorable lipid profile. There is clear evidence that excess saturated fat in the diet has a detrimental effect on lipid profiles, and therefore restriction of saturated fat is recommended. The data supporting absolute restriction of carbohydrates are not robust, so the ADA guidelines allow flexibility in intake of carbohydrates and nonsaturated fat. Separate guidelines have been published about the carbohydrate content and composition of the diet.8
Box 1 Goals of Medical Nutrition Therapy
Adapted from Bantle JP, Wylie-Rosett J, Albright AL, et al: Nutrition recommendations and interventions for diabetes—2006: A position statement of the American Diabetes Association. Diabetes Care 2006;29:2140-2157.
For All Persons With Diabetes
The most important variable in prandial glycemic excursion is total carbohydrate intake. Low glycemic index foods consumed alone result in lower prandial glucose excursion than high glycemic index foods. However, in the context of a mixed meal, differences between low and high glycemic index foods are attenuated. The amount8–10 and source10,11 of carbohydrates are important determinants of postprandial glucose. The relative effects of each have been recently studied. Brand-Miller and colleagues12,13 have reported that they analyzed the relative impact of the glycemic index and total carbohydrate content of individual foods on glycemic load—the product of glycemic index and total grams of carbohydrate—using linear regression analysis. Carbohydrate content (total grams) alone explained 68% of the variation in glycemic load, and the glycemic index of the food explained 49%. When total carbohydrate and glycemic index were both included in the regression analysis, the glycemic index accounted for 32% of the variation.
Restriction of alcohol and sodium is generally advised. Supplements are not necessary in patients who are otherwise consuming a well-balanced diet. Many recommendations for weight management propose restriction of calories based on the degree of obesity and propose 30 to 45 minutes of exercise 3 to 5 days a week. Exercise is an important component of any regimen for weight reduction and glycemic control. Other nutritional guidelines for patients with diabetes are generally consistent with the ADA guidelines.5,14–28
Exercise
Guidelines for exercise have not always been specific with regard to exact exercise prescriptions, especially regarding aerobic and resistance exercises.14,29,30 The commonly proposed recommendation that 150 minutes of moderate-intensity (or 90 minutes of vigorous) aerobic exercise a week is generally the amount of exercise required to achieve benefits on glycemic control and reduce coronary heart disease (CHD) risk and has been supported by ADA/American Heart Association (AHA) recommendations.6,7
Regular exercise is encouraged, but complications of diabetes need to be taken into account. Injury to patients with loss of sensation in their feet is a limitation for weight-bearing exercise. Because of risk of CHD in patients with diabetes, appropriate screening for CHD should be performed before patients engage in any rigorous exercise program.14,17,29–32 Benefits of exercise include weight control and improved glycemic control, often due to improvement in insulin resistance.
COMPLICATIONS
The complications of diabetes include retinopathy, nephropathy, neuropathy, and increased risk for atherosclerotic vascular disease. Diabetes is the leading cause of blindness in young people and is comparable with macular degeneration as a cause of blindness in older adults. DM is the leading cause of end-stage renal disease requiring dialysis or transplantation. DM is the leading cause of nontraumatic amputations of the lower extremity, a result of peripheral neuropathy and peripheral vascular disease. DM is associated with a twofold to fivefold increased risk for CHD.33
Two large trials—the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS)—have demonstrated clear relation between glucose control and the risks for retinopathy (onset and progression), nephropathy (measured by albuminuria), and neuropathy (clinical and electromyographic measures).34–38 The relation between the degree of hyperglycemia and CHD risk has also been established.39,40 Risk begins well below the glycemic threshold for the diagnosis of diabetes.23,25–28,41,42
Screening
Patients should be screened for diabetic complications (Table 1).
Diabetic Retinopathy
Dilated eye examinations by ophthalmologists or optometrists should be performed within 5 years of onset in T1DM and at the time of diagnosis in T2DM, because the actual date of onset is unknown in T2DM.14,29 Follow-up examinations should be performed annually in patients with no or minimal background retinopathy. More frequent follow-up examinations should be performed in patients who have more advanced retinopathy. Handheld ophthalmoscopy in the office may be able to detect diabetic retinopathy but offers limited view of the retina and difficulty detecting diabetic macular edema. Macular edema is a significant cause of vision loss in DM. Macular edema is easier to detect with binocular vision and, in difficult cases, IV fluorescein angiography and confocal microscopy are used. Technology is available for screening with fundus photographs obtained in the physician’s office and then read by an experienced reader. However, these methods are not yet sufficiently standardized to use as routine screening tools.
Diabetic Nephropathy
The hallmark of early diabetic nephropathy is albumin excretion. Sensitive assays to detect very low levels of albumin, or microalbuminuria, have been available for many years.14,29 The simplest screening measure is a spot urine test adjusted for the urine creatinine level. Timed overnight collections and 24-hour collections may also be used. In general, microalbuminuria is defined as more than 30 mg albumin per gram of creatinine (spot urine test) or 30 to 299 mg per 24 hours and more than 300 mg/g creatinine (or 24 hours) as albuminuria. Serum creatinine determinations should be performed at least annually in patients with albuminuria; when estimated glomerular filtration rate (GFR) values are declining, more-specific measures of GFR (most commonly, creatinine clearance) should be used.
Peripheral Neuropathy
Monofilament testing in the office is the easiest way to test for the insensate foot.43–50 The 5.07-mm monofilament should be applied to the bottoms of the feet (Fig. 1).50 Any loss of sensation is associated with an increased risk for ulcer formation. Any patient who has had a foot ulcer is at increased risk for further foot ulcers.
Figure 1 Nylon monofilament test.
(From Armstrong DG, Lavery LA: Diabetic foot ulcers: Prevention, diagnosis and classification. Am Fam Physician 1998;57:1325-1328.)
Coronary Heart Disease
Various studies have considered the issue of screening for CHD.14,17,29,51–54 The guidelines and individual recommendations are not entirely concordant. Whereas nearly every group suggests stress tests for patients with symptoms of CHD or electrocardiographic changes suggesting ischemia, recommendations on screening for asymptomatic disease are less consistent. The ADA considers that candidates for a screening cardiac stress test should include those with a history of peripheral or carotid occlusive disease; persons with a sedentary lifestyle, who are older than 55 years, and who plan to begin a vigorous exercise program; and two or more of the risk factors noted earlier.29 The American Association of Clinical Endocrinologists (AACE) guidelines state:
Screening for asymptomatic coronary artery disease is an important consideration in patients with diabetes. An appropriate protocol for such screening has not been adequately tested. Increasing age, gender, cardiovascular risk factors, microalbuminuria, and retinopathy may identify high-risk groups for whom such testing is indicated.14
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