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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 and is a leading contributor to coronary heart disease (CHD). Diabetes-associated microvascular complications usually do not appear until the second decade of hyperglycemia. In contrast, diabetes-associated CHD risk, related in part to insulin resistance and its resultant dyslipidemeia, 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 mitigated with aggressive glycemic, lipid, and blood pressure control, as well as efforts at early detection.
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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 405-1). 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 additional pathophysiologic features that are shared with the general population. Nonvascular complications include infections, skin changes, hearing loss, and increased 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. 405-1). Evidence implicating a causative role for chronic hyperglycemia in the development of macrovascular complications is less conclusive as other factors such as dyslipidemia and hypertension also play important roles in macrovascular complications. CHD events and mortality rate are two to four times greater in patients with type 2 DM, correlate with fasting and postprandial plasma glucose levels as well the hemoglobin A1c (HbA1c), and can be reduced by intensive diabetes management as demonstrated in patients with type 1 DM.
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