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Older adults frequently report decreased vitality, which has a host of underlying causes. This chapter deals with metabolic factors that may lead to decreased energy in the older adults: endocrine disease, anemia, poor nutrition, and infection. Lack of exercise is discussed in Chapter 5.
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Carbohydrate Metabolism
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Approximately 50% of older people have glucose intolerance with normal fasting blood sugar levels. Although poor diet, obesity, and lack of exercise may account for some of these findings, aging itself is associated with deteriorating glucose tolerance, primarily attributable to a change in peripheral glucose utilization, although beta-cell dysfunction and decreased insulin secretion are also contributing factors. Glucose intolerance alone is not sufficient to diagnose diabetes mellitus. However, such individuals are at increased risk of developing diabetes mellitus. Prediabetes is identified as impaired fasting glucose (fasting plasma glucose level of 100-125 mg/dL), as impaired glucose tolerance (plasma glucose level of 140-199 mg/dL 2 hours after 75 g of glucose), or as a glycosylated hemoglobin of 5.7% to 6.4% (diagnosis of diabetes and prediabetes is reviewed in Inzucchi, 2012). Lifestyle modification, including weight loss and exercise, prevents or forestalls the development of type 2 diabetes in individuals with glucose intolerance (Diabetes Prevention Program Research Group, 2002; reviewed in Gillies et al., 2007). Both the U.S. Preventive Services Task Force (USPSTF) and the American Diabetes Association (ADA) recommend these interventions for patients at risk for diabetes (U.S. Preventive Services Task Force, 2003).
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More than 25% of individuals age 65 and older in the United States have diabetes mellitus (Ligthelm et al., 2012). Many of these patients are unaware that they have the disease. The USPSTF concludes that the evidence is insufficient to recommend for or against routinely screening asymptomatic adults for type 2 diabetes, except that those with hypertension or hyperlipidemia should be screened as an approach to reducing cardiovascular risk. The ADA recommends that screening should begin at age 45 at 3-year intervals, but at shorter intervals in high-risk patients. The diagnosis of diabetes should be made based on a fasting plasma glucose level of ≥126 mg/dL or a glycosylated hemoglobin of ≥6.5% and confirmed by either test. Initial evaluation in patients with type 2 diabetes should include glycosylated hemoglobin level, fasting lipid profile, basic metabolic panel, urine dipstick for overt proteinuria or screen for microalbuminuria, and electrocardiography.
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The therapeutic goal for relatively healthy, nonfrail older diabetic patients is the same as that for younger patients: normal fasting plasma glucose without hypoglycemia. According to the American Geriatrics Society, the Canadian Diabetes Association, the ADA, and the European Diabetes Working Party, a hemoglobin A1c (HbA1c) value of 7% or less is reasonable for healthy and well-functioning adults. However, in frail individuals and those with short life expectancies (including many nursing home residents), the therapeutic goal may be modified to eliminate symptoms associated with hyperglycemia, to reduce hypoglycemia, and to enhance ...