Abbreviations: CVD > cardiovascular disease DPP > Diabetes Prevention Program FPG > fasting plasma glucose IFG > impaired fasting glucose IGT > impaired glucose tolerance NNT > number needed to treat OGTT > oral glucose tolerance test TRIPOD > Troglitazone in Prevention of Diabetes
Recent Clinical Practice Recommendations 2003 by American Diabetes Association have indicated that there are now interventions capable of delaying the onset of diabetes. Most of the diabetes prevention trials required that subjects have IGT (defined as an FPG level <140 mg/dl and a 2-h OGTT value between 140 and 199 mg/dl) as the main enrollment criterion.
The strategies effective in preventing diabetes should rely on :
- Lifestyle modification or
- Glucose-lowering drugs that have been approved for treating diabetes.
The greater benefit of weight loss and physical activity strongly suggests that lifestyle modification should be the first choice to prevent or delay diabetes. Modest weight loss (5–10% of body weight) and modest physical activity (30 min daily) are the recommended goals. Because this intervention not only has been shown to prevent or delay diabetes, but also has a variety of other benefits, health care providers should urge all overweight or sedentary individuals to adopt these changes, and such recommendations should be made at every opportunity.
Drug therapy to prevent or delay diabetes appears to be much less beneficial for a variety of reasons. First, when compared directly with lifestyle modification, at least metformin was considerably less efficacious overall, and the advantage of lifestyle modification was even greater in older or less overweight patients . The relative risk reduction using acarbose appears similar to that of metformin, although the study participants were very different. Second, all glucose-lowering drugs require monitoring, have been associated with significant adverse side effects, and are contraindicated in some individuals. Third, none of the glucose-lowering agents tested or commercially available have been studied with regard to protection against CVD or have any other clinical benefit to non-diabetic individuals. Even in people with diabetes, there is only one glucose-lowering agent (metformin) for which there is any outcome data to suggest possible effectiveness in reducing the incidence of macrovascular disease . Finally, prescribing a medication to delay the onset of diabetes, which is also used to treat diabetes, will increase a patient’s total years of drug exposure and may increase the likelihood of untoward drug effects.
Recommendations to prevent or delay diabetes
- Individuals at high risk for developing diabetes need to become aware of the benefits of modest weight loss and participating in regular physical activity. (A)
- Screening: based on current screening guidelines for diabetes (49), men and women 45 years of age, particularly those with a BMI 25 kg/m2*, are candidates for screening to detect pre-diabetes (IFG or IGT). Screening should be considered in younger individuals with a BMI 25 kg/m2* who have additional risk factors (Table 3). (B)
- In individuals with normoglycemia, rescreening at 3-year intervals is reasonable. (C)
- How to screen: screening should be carried out only as part of a health care office visit. Either an FPG test or 2-h OGTT (75-g glucose load) is appropriate, and positive test results should be confirmed on another day. (B)
- Intervention strategy: patients with pre-diabetes (IFG or IGT) should be given counseling on weight loss as well as instruction for increasing physical activity. (A)
- Follow-up counseling appears important for success. (B)
- Monitoring for the development of diabetes should be performed every 1–2 years. (E)
- Close attention should be given to, and appropriate treatment given for, other CVD risk factors (e.g., tobacco use, hypertension, dyslipidemia). (A)
- Drug therapy should not be routinely used to prevent diabetes until more information is known about its cost-effectiveness. (E)
* May not be correct for all ethnic groups.
Therefore, when all factors are considered, there is insufficient evidence to support the use of drug therapy as a substitute for, or routinely used in addition to, lifestyle modification to prevent diabetes. Until there are studies showing that drugs will delay or prevent the complications of diabetes, or until the cost-effectiveness of using pharmacological agents has been established, ADA does not recommend the routine use of these agents to prevent diabetes. For now it seems that, lifestyle intervention to prevent diabetes appears to be very safe, and, therefore, regular monitoring for untoward effects is unnecessary.