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Essentials of Diagnosis

  • Hemoglobin A1c ≥6.5, or

  • Fasting (no caloric intake for ≥8 hours) plasma glucose ≥126 mg/dL (7.0 mmol/L), or

  • Symptoms of hyperglycemia plus random plasma glucose ≥200 mg/dL (11.1 mmol/L), or

  • 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during a 75-g oral glucose tolerance test.

General Principles in Older Adults

Diabetes mellitus (DM) is a common condition in older adults and is associated with increased risk of morbidity and mortality. The prevalence of DM (diagnosed and undiagnosed) in the U.S. population of older adults has been estimated at 10.9 million, or 27% of people older than age 65 years. If current trends continue, 16.8 million adults older than age 65 will have diabetes by 2050. There are many reasons for the increasing prevalence of diabetes in older adults, including declining beta cell function, relative insulinopenia, and insulin resistance. Furthermore, the risk of developing DM type 2 increases with obesity, lack of physical activity, and loss of muscle mass, all of which commonly occur with aging. Compared to younger people with diabetes, people older than age 65 years tend to have longer duration of diabetes, with a median duration of 10 years, higher rates of diabetic complications and comorbid disease, and more functional dependence.

The population of older adults with diabetes is incredibly diverse. Some older adults have had type 1 diabetes for many decades and reach old age with significant end-organ complications. Others develop insulin resistance and diabetes in their 70s or 80s, and have no clear evidence of related complications. Some are able to effectively self-manage their disease, whereas others cannot because of cognitive, visual, or functional impairments. Thus, the management of an older patient with diabetes must account for this tremendous heterogeneity and decision making should be individualized, focusing on patient factors such as the duration of diabetes, presence of complications, comorbid conditions, life expectancy, patient goals and preferences, and functional abilities.

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Boyle  JP, Honeycutt  AA, Narayan  KM  et al Projection of diabetes burden through 2050: impact of changing demography and disease prevalence in the U.S. Diabetes Care. 2001;24(11): 1936-–1940.
CrossRef  [PubMed: 11679460]
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Centers for Disease Control and Prevention (CDC). National Diabetes Fact Sheet: National Estimates and General Information on Diabetes and Prediabetes in the United States, 2011. Atlanta, GA: Centers for Disease Control and Prevention US Department of Health and Human Services, 2011.

Pathogenesis

Most patients older than 65 years with diagnosed DM have type 2 DM and a small minority has type 1 DM. Type 1 DM is an autoimmune disease in which pancreatic beta cells are destroyed, resulting in absolute insulinopenia, subsequent hyperglycemia, and risk for ketoacidosis. Exogenous insulin is required for survival and glucose control.

In contrast, type 2 DM results from insulin resistance, increased insulin requirements to maintain euglycemia and ultimately, relative insulin deficiency when ...

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