The evidence base for tight blood pressure control in the management of type 2 diabetes mellitus.

Diabetes mellitus is a leading cause of morbidity and death in the United States. Type 2 diabetes mellitus accounts for the majority of affected persons (90% to 95%) and affects older adults, particularly those older than 50 years of age. It affects an estimated 16 million Americans, 11 million of whom have both diabetes and hypertension (1). Most adverse diabetes outcomes are a result of vascular complications. These complications are generally classified as microvascular, such as retinopathy, nephropathy, and neuropathy (although neuropathy may not be entirely a microvascular disease), or macrovascular, such as coronary artery disease, cerebrovascular disease, and peripheral vascular disease. In order to prevent, or diminish the progression of, microvascular and macrovascular complications, recommended diabetes management necessarily encompasses both metabolic control and cardiovascular risk factor control (2–4). The need for good glycemic control is supported by the Diabetes Control and Complications Trial (5) in type 1 diabetes mellitus and, more recently, the United Kingdom Prospective Diabetes Study (UKPDS) in type 2 diabetes mellitus (6). In these studies, tight blood sugar control reduced microvascular complications, such as nephropathy and retinopathy, but had little effect on macrovascular outcomes. Up to 80% of patients with type 2 diabetes mellitus will develop or die of macrovascular disease, underscoring the importance of preventing macrovascular complications. In an effort to provide internists and other primary care physicians with effective management strategies for diabetes care, the American College of Physicians decided to develop guidelines on the management of hypertension in people with type 2 diabetes mellitus. The target audience for this guideline is all clinicians who provide care to patients with type 2 diabetes. The target patient population is all persons with type 2 diabetes who have hypertension, defined as systolic blood pressure of at least 140 mm Hg or diastolic blood pressure of at least 90 mm Hg. This target patient population includes those who already have some form of microvascular complication and, of particular importance, premenopausal women with diabetes. We will attempt to answer the following questions: 1) What are the benefits of tight blood pressure control in type 2 diabetes? 2) What should the target levels of systolic blood pressure and diastolic blood pressure be for patients with type 2 diabetes? and 3) Are certain antihypertensive agents more effective or beneficial in patients with diabetes? When analyzing benefit or effectiveness for this review, we included only studies that measured clinical end points. The four major classes of clinical end points were all-cause mortality, cardiovascular mortality, cardiovascular events (myocardial infarction, stroke, or congestive heart failure), and microvascular complications (photocoagulation, nephropathy, neuropathy, or amputation). The review was divided into two categories. The first included studies that evaluated the effects of blood pressure control if the comparison examined an antihypertensive drug versus placebo or the effects of different target blood pressure levels. The second category evaluated the effect of different classes of drugs. A discussion of this evidence follows.