A 68-year-old woman is re-evaluated after laboratory studies show a fasting plasma glucose level of 113 mg/dL (6.3 mmol/L). She has a family history of type 2 diabetes mellitus.
On physical examination, blood pressure is 142/88 mm Hg and BMI is 29. Other vital signs and examination findings are normal.
She undergoes an oral glucose tolerance test, during which her 2-hour plasma glucose level increases to 135 mg/dL (7.5 mmol/L).
The most appropriate treatment for this patient is diet and exercise. She has impaired fasting glucose (IFG), defined as a fasting plasma glucose level in the range of 100 to 125 mg/dL (5.6 to 6.9 mmol/L), and should begin a program of intensive lifestyle change, including 30 minutes of exercise most days of the week and a calorie-restricted diet, to achieve weight reduction on the order of 7% of body weight.
Diet and exercise is the recommended approach for patients with either IFG or impaired glucose tolerance (IGT), the prediabetic states. The relative risk reduction (RRR) in the incidence of diabetes in patients with IGT associated with intensive lifestyle change is 58%.
Pharmacologic therapy with glucose-lowering drugs is not indicated for this patient with isolated IFG. In pharmacologic studies of diabetes prevention, acarbose therapy resulted in only a 25% RRR, which is inferior to that obtained with diet and exercise.
Metformin therapy is associated with an RRR of 31%, which is also inferior to the 58% RRR obtained with diet and exercise. Metformin therapy may be considered in patients with both IFG and IGT, who constitute a higher risk group. This patient does not have IGT (fasting plasma glucose level of 140 to 199 mg/dL [7.7 to 11.0 mmol/L] at the 2-hour mark of an oral glucose tolerance test) and so should not receive metformin.
Modulators of the renin-angiotensin axis, such as ramipril and other angiotensin-converting enzyme inhibitors, do not contribute to diabetes prevention.
Rosiglitazone and pioglitazone have been associated with 62% and 81% RRRs, respectively, in the incidence of diabetes. These agents, however, are not endorsed for routine pharmacologic use in patients with prediabetes because of their costs and adverse effects, including edema, increased fracture risk in women, and possible increased cardiovascular morbidity.
- Patients with prediabetes should be advised to adopt a program of lifestyle change to prevent progression to type 2 diabetes mellitus.