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elderly patients
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Loss of body mass is a hallmark of aging, with loss of 40 percent or more of fat-free mass being incompatible with life. The terms wasting, cachexia, and sarcopenia are often used to describe and differentiate types of weight loss.
Wasting is the unintentional loss of weight including both fat and fat-free compartments, and is driven largely by inadequate dietary intake. Cachexia on the other hand, refers to loss of fat-free mass and especially body cell mass but with little or no weight loss, and is related to increased protein degradation. Sarcopenia refers to loss of muscle mass specifically and seems to be an intrinsic age-related condition.
Sarcopenia, the loss of muscle mass and strength with age, is becoming recognized as a major cause of disability in the elderly population. Sarcopenia is part of normal aging and does not require a disease to occur although muscle wasting is accelerated by chronic diseases. Sarcopenia is thought to have multiple causes - neurological, hormonal, nutritional, and physical activity-related changes with age.
Declines are due primarily to alterations in the body cell mass compartment. This compartment is functionally the most important compartment in determining energy expenditure, protein needs, and metabolic response to physiologic stress. Candidate mechanisms include loss of alpha motor neurons in the spine, loss of endogenous growth hormone production, dysregulation of cytokines, loss of estrogen and androgen production, inadequate protein intake, and reduced physical activity leading to a reduction in the number and size of type II muscle fibers. In aging, of the subcompartments of body cell mass, it is muscle cell mass that declines to the greatest extent.
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Guo SS, et al. Aging, body composition, and lifestyle: the Fels Longitudinal Study. American Journal of Clinical Nutrition, 1999; 70: 405-11. |
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Omran ML, Morley JE. Assessment of protein energy malnutrition in older persons, part I: History, examination, body composition, and screening tools. Nutrition, 2000 Jan;16(1):50-63. |
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Berger VA, et al. Reproducibility of body composition and body water spaces measurements in healthy elderly individuals. The Journal of Nutrition, Health & Aging, 2000;4(4):24305. |
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Hughes VA, Evans WJ. Assessment of fat-free mass in an older population using bioelectrical impedance. Federation Proceedings, 46(4), 1987. |
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Roubenoff R, et al. Nutrition assessment in long-term care facilities. Nutrition Review, 1996 Jan;54(1 Pt 2):S40-2. |
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