Controlling Blood Glucose Levels in Patients with Type 2 Diabetes Mellitus An Evidence-Based Policy Statement by the American Academy of Family Physicians and American Diabetes Association
Steven H. Woolf, MD, MPH Mayer B. Davidson, MD Sheldon Greenfield, MD Hanan S. Bell, PhD Theodore G. Ganiats, MD Michael D. Hagen, MD Valerie Anne Palda, MD, MSc Robert A. Rizza, MD Stephen J. Spann, MD Fairfax, Virginia; Los Angeles, California; Boston, Massachusetts; Seattle, Washington;San Diego, California; Lexington, Kentucky; Toronto, Canada; Rochester, Minnesota; and Houston, Texas Submitted, revised, March 6, 2000. From the Department of Family Medicine, Medical College of Virginia-Virginia Commonwealth University, Richmond (S.H.W.); the Clinical Trials Unit, Charles R. Drew University of Medicine and Science, and the Department of Medicine, University of California-Los Angeles School of Medicine (M.B.D.); the Department of Medicine, Tufts University School of Medicine, Medford (S.G.); the American Academy of Family Physicians, Leawood (H.S.B.); the Department of Family and Preventive Medicine, University of California-San Diego School of Medicine (T.G.G.); the Department of Family Practice, University of Kentucky College of Medicine, Lexington (M.D.H.); the Department of Medicine, University of Toronto (V.A.P.); the Division of Endocrinology, Metabolism and Nutrition, Mayo Clinic and Foundation, Rochester (R.A.R.); and the Department of Family and Community Medicine Baylor College of Medicine, Houston (S.J.S.). Reprint requests should be addressed to Steven H. Woolf, Department of Family Practice, Virginia Commonwealth University, Medical College of Virginia Campus, 3712 Charles Stewart Drive, Fairfax, VA 23298-0251. E-mail: SHWoolf@aol.com.
References
OBJECTIVE: To review evidence about the benefit of intensive glycemic control for patients with type 2 diabetes and to develop practice recommendations.
PARTICIPANTS: A 9-member panel composed of family physicians, general internists, endocrinologists, and a practice guidelines methodologist was assembled by the American Academy of Family Physicians, the American Diabetes Association, and the American College of Physicians.
EVIDENCE: Admissible evidence included published randomized controlled trials and observational studies regarding the effects of glycemic control on microvascular and macrovascular complications and on adverse effects. We followed systematic search and data abstraction procedures. Greater weight was given to clinical trials and to evidence about health outcomes.
CONSENSUS PROCESS: Interpretations of evidence and approval of documents were finalized by unanimous vote, with recommendations linked to evidence and not expert opinion. The full report was prepared by the chair and 2 panel members, representing each of the 3 organizations. The initial draft underwent external review by 14 diabetologists and family physicians and changes consistent with the evidence were incorporated.
CONCLUSIONS: The evidence demonstrates that the risk of microvascular and neuropathic complications is reduced by lowering glucose concentrations. Whether glycemic control affects macrovascular outcomes is less clear. The potential benefits of glycemic control must be balanced against factors that either preempt benefits (eg, limited life expectancy, comorbid disease) or increase risk (eg, severe hypoglycemia). The magnitude of benefit is a function of individual clinical variables (eg, baseline glycated hemoglobin level, presence of preexisting microvascular disease). Appropriate targets for treatment should be determined by considering these factors, patients’ risk profiles, and personal preferences.
CLINICAL QUESTION
What are the benefits and risks of glycemic control in type 2 diabetes, and what are the implications for clinical practice?
An estimated 16 million people in the United States have diabetes.1 Its microvascular complications (retinopathy, nephropathy, neuropathy) are a leading cause of blindness among adults,2 end-stage renal disease,3 and lower-extremity amputations.4 Its macrovascular complications pose an even greater public health burden, increasing the risk of coronary artery disease, stroke, and peripheral vascular disease.5 Each year diabetes costs the country an estimated $90 billion to $99 billion.6,7
Type 2 diabetes, which accounts for 90% to 95% of diabetes cases,8 differs from type 1 disease in average age of onset and etiology. In both forms, however, the underlying cause of microvascular (and possibly macrovascular) complications appears to be chronic elevations in blood glucose concentrations. The overriding factors in predicting microvascular pathogenesis have less to do with the type of diabetes than with the number of years the patient has had hyperglycemia and the magnitude of the glucose elevation.
In recent years, 2 major randomized controlled trials (RCTs), the Diabetes Control and Complications Trial9 (DCCT) in patients with type 1 disease and the United Kingdom Prospective Diabetes Study10 (UKPDS) in patients with type 2 diabetes, have shown that microvascular complications can be reduced significantly in patients who achieve normal or near-normal blood glucose levels. There is now agreement in the medical community about the importance of lowering markedly elevated blood glucose levels.
The incremental benefit of tight glycemic control (as opposed to less intensive therapy) varies across patient groups, however. Years are required for microvascular complications to progress to symptomatic disease. Patients with type 1 diabetes, who are generally younger, are more likely to live long enough to benefit from tight glycemic control than patients with type 2 disease, who face a shorter life expectancy because of their age and risk of cardiovascular disease. For patients with coexistent diseases, the delayed benefits of glycemic control may be offset by the more immediate inconvenience, complications, and costs of intensive treatment and by the health effects of comorbid conditions.
These generalizations do not apply to all patients. The older age of onset of type 2 diabetes is a population average with a wide distribution. Many patients with type 2 diabetes live long enough to experience significant microvascular disease and may benefit from glycemic control. Also, interventions that extend life expectancy (eg, smoking cessation, blood pressure control, and lipid control) give patients more time to encounter advanced microvascular disease and an opportunity to benefit from treatment.
In 1996, the American Academy of Family Physicians convened a panel to conduct a systematic review of the evidence of the benefits and harms of glycemic control in type 2 diabetes and to develop evidence-based recommendations. The 9-member panel included family physicians, general internists, endocrinologists, and a practice guidelines methodologist. Four members were appointed by the American Diabetes Association and the American College of Physicians. We summarize the panel’s findings, which are available in a full report.*
