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Diabetes-related complications affect many organ systems and are responsible for the majority of morbidity and mortality associated with the disease. For many years in the United States, diabetes has been the leading cause of new blindness in adults, renal failure, and nontraumatic lower extremity amputation. More recently, diabetes has also emerged as a leading contributor to coronary heart disease (CHD). Diabetes-associated complications related to hyperglycemia usually do not appear until the second decade of hyperglycemia. In contrast, diabetes-associated CHD risk, related in part to insulin resistance, may develop before hyperglycemia is established. Because type 2 diabetes mellitus (DM) often has a long asymptomatic period of hyperglycemia before diagnosis, many individuals with type 2 DM have both glucose-related and insulin resistance-related complications at the time of diagnosis. Fortunately, many of the diabetes-related complications can be prevented or delayed with a focus on diet, fitness, early detection, aggressive glycemic control, and efforts to minimize the risks of complications. Recent studies show a decline in diabetes-related complications in individuals, but this is tempered by the increase in the number of individuals with diabetes. For example, the rate of myocardial infarction (MI) associated with diabetes declined by 67% between 1990 and 2010.
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Diabetes-related complications can be divided into vascular and nonvascular complications and are similar for type 1 and type 2 DM (Table 398-1). The vascular complications of DM are further subdivided into microvascular (retinopathy, neuropathy, nephropathy) and macrovascular complications (CHD, peripheral arterial disease [PAD], cerebrovascular disease). Microvascular complications are diabetes-specific, whereas macrovascular complications have pathophysiologic features that are both shared with the general population and diabetes-specific. Nonvascular complications include infections, skin changes, and hearing loss. Some studies suggest that 2 DM increases the risk of dementia and impaired cognitive function.
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GLYCEMIC CONTROL AND COMPLICATIONS
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The microvascular complications of both type 1 and type 2 DM result from chronic hyperglycemia (Fig. 398-1). Evidence implicating a causative role for chronic hyperglycemia in the development of macrovascular complications is less conclusive. CHD events and mortality rate are two to four times greater in patients with type 2 DM and correlate with fasting and postprandial plasma glucose levels as well the hemoglobin A1c (HbA1c). Other factors such as dyslipidemia and hypertension also play important roles ...