Effectiveness of diabetes management: is improvement feasible?

Abstract

The estimated prevalence of diabetes among adults was 7.4% in 1995 and is expected to increase to about 9% in 2025 (1). Type 2 diabetes is frequently diagnosed many years after the onset of hyperglycemia because it develops gradually and is asymptomatic at the earlier stages. Life expectancy is about 8 years shorter for adults with diabetes aged 55 to 64 years than for nondiabetic subjects, and 4 years shorter for those aged 65 to 74 years (2). Cardiovascular disease is the cause of most deaths (approximately 70%); hence, prevention and treatment of cardiovascular disease are important in reducing mortality (2). Type 2 diabetes, which is an independent risk factor for macrovascular disease, increases the risk of coronary events twofold in men and fourfold in women (1). The incidence of cardiovascular disease in diabetic patients without prior myocardial infarction is similar to that in nondiabetic patients who have had a prior myocardial infarction, after adjustment for age, sex, and other cardiovascular risk factors (3). The 1-year fatality rate after the first myocardial infarction is significantly higher in diabetic patients (4). Importantly, about half of those who die do so before they reach the hospital, emphasizing the importance of primary prevention of cardiovascular risk factors before the onset of clinical coronary heart disease. Diabetes is commonly associated with hypertension and dyslipidemia, each of which increases the already high risk of cardiovascular disease in diabetic patients. The prevalence of hypertension in patients with type 2 diabetes is higher than in the general population, affecting 20% to 60% of those with diabetes. Hypertension exacerbates the vascular complications of diabetes, including renal disease, coronary heart disease, stroke, peripheral vascular disease, lower extremity amputations, and retinopathy. Several studies have documented the beneficial effect of treating hypertension on clinical outcomes. In the Hypertension Optimal Treatment trial, the risk of major cardiovascular events was halved in patients with a diastolic blood pressure 80 mm Hg in comparison with 90 mm Hg (5), whereas another study reported that tight control of blood pressure (mean, 144/82 mm Hg) in patients with hypertension and type 2 diabetes significantly reduced the risk of endpoints related to diabetes, death, stroke, microvascular disease, and heart failure (6). The recommended blood pressure in patients with diabetes is 130/80 mm Hg (7), and 125/75 mm Hg for those with proteinuria 1g/d. The excessive risk of coronary heart disease can be partly explained by an increased prevalence of lipid abnormalities in patients with diabetes. The United Kingdom Prospective Diabetes Study (UKPDS) showed that the risk factors for coronary heart disease (fatal and nonfatal myocardial infarction, angina pectoris) were high low-density lipoprotein (LDL) cholesterol, low highdensity lipoprotein (HDL) cholesterol, hemoglobin A1c(HbA1c) levels, diastolic blood pressure, and smoking. Whereas previous trials of statins reported a decrease in cardiovascular and all-cause mortality in nondiabetic subjects, a recent study suggested that this benefit was similar in patients with diabetes (8). The recommended goal for lipids in patients with diabetes is an LDL cholesterol level 100 mg/dL and a non-HDL cholesterol level 130 mg/dL. There is strong evidence of a substantial benefit of aspirin in the primary and secondary prevention of cardiovascular events in diabetic patients (5,9). Aspirin therapy (75 to 325 mg/d) is recommended for primary prevention in diabetic patients 30 years who have one or more cardiovascular risk factors, as well as in all adult diabetic patients who have macrovascular disease (1). Whereas interventions aimed at reducing macrovascular complications have demonstrated effectiveness, interventions that achieve near normal blood glucose concentrations have been shown to reduce microvascular complications, as was reported in the UKPDS (10). Thus, based on an increasing number of well-performed, well-powered, randomized clinical trials, there is substantial evidence that we have a pharmacological armamentarium that can be highly effective in improving mortality and reducing complications in patients with type 2 diabetes. However, how good are we at applying these therapies in clinical practice? In this issue of The American Journal of Medicine, Grant et al. (11) evaluate the effectiveness of clinical management of hyperglycemia, hypertension, and hyperchoAm J Med. 2002;112:670 – 672. From the Division of Endocrinology, Gerontology and Metabolism (MB, FBK), Department of Medicine, Stanford University, Stanford, California; and the VA Palo Alto Health Care System (FBK), Palo Alto, California. Manuscript submitted January 26, 2002.