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INTRODUCTION AND EPIDEMIOLOGY

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Type 2 diabetes mellitus (T2DM) is a complex, chronic metabolic disorder characterized by hyperglycemia and associated with a relative deficiency of insulin production, along with a reduced response of the target tissues to insulin. It is a major public health issue and an important contributor to morbidity and mortality all over the world.1 The top three countries with the highest number of diabetic patients are, in decreasing order, India, China, and the United States.2 Epidemiology is summarized in Table 224-1.

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TABLE 224-1Epidemiology of Type 2 Diabetes Mellitus (T2DM)
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T2DM is more common among women than men, and its prevalence increases by age. The prevalence of T2DM among youth is rising dramatically. Investigators attribute this rise to patterns of obesity and lack of physical activity. Native Americans, blacks, and Americans of Mexican or Japanese ethnicity are more commonly affected by T2DM than non-Hispanic whites (Figure 224-1).

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FIGURE 224-1.

Estimated age-adjusted total prevalence of diabetes in people age 20 years or older, by race/ethnicity—United States, 2005. [Reproduced from the Centers for Disease Control and Prevention: National diabetes fact sheet: general information and national estimates on diabetes in the United States, 2005. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2005.]

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Diabetes reduces the life expectancy of its victims by approximately 10 years. Mortality and morbidity increase because of increased risk of cardiovascular disease, heart disease and stroke, visual impairment, renal disease, and amputations. The utilization of health care, including emergency care, is higher in patients with diabetes compared with that of nondiabetic subjects. The relative risk is estimated to be 1.23 (95% confidence interval [CI], 1.08–1.39) before the diagnosis and 2.41 (95% CI, 2.18–2.66) after diagnosis is made.3

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PATHOPHYSIOLOGY

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T2DM is a complex heterogeneous metabolic disorder, characterized by chronic elevation of plasma glucose levels. The pathogenesis is complex and involves interaction of both genetic (usually polygenic) and environmental (often lifestyle-related) factors. The most important pathophysiologic features of T2DM are decreased insulin sensitivity (insulin resistance) and impaired insulin secretion (Figure 224-2).

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FIGURE 224-2.

Pathophysiology of type 2 diabetes mellitus. IFG = impaired fasting glucose; ...

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