5. DETERMINE (13–15)
9.1 NUTRITIONAL FRAILTY: A REVISED DEFINITION BASED ON ETIOLOGY
During the time since the first edition of this book addressed the topic of nutritional frailty, substantial progress has been made toward the characterization and understanding of the causes of unintentional weight loss in older adults. Thanks to an on-going international effort to develop a consensus definition of cachexia(1) and comprehensive work characterizing the natural course of sarcopenia (2–5), there is now a much better understanding of the unique contributions that loss of
From:Nutrition and Health: Handbook of Clinical Nutrition and Aging, Second Edition Edited by: C. W. Bales and C. S. Ritchie, DOI 10.1007/978-1-60327-385-5_9,
!Humana Press, a part of Springer ScienceþBusiness Media, LLC 2009 157
appetite and poor food intake make to the overall phenomenon of weight loss and tissue wasting in older patients. Thus, while acknowledging that often more than one condition exists in a given older individual (see Fig. 9.1), this edition of the Handbookincludes separate discussions of undernutrition-related weight loss (this chapter), sarcopenia (Chapter 10), and cachexia (Chapter 11). This chapter explores the development of nutritional frailty as specifically defined, its contri- bution to overall frailty(6), and potential interventions to lessen its detrimental effects.
9.1.1. Definitions and Risk Factors
Table 9.1 lists definitions for a number of salient terms; the one most integral to this chapter is the definition of nutritional frailty, which is an unintentional, precipitous loss of both lean and fat mass resulting almost entirely from a reduc- tion in food intake. In contrast, sarcopenia is an age-related loss of muscle and cachexia is a complex metabolic syndrome associated with underlying illness and (often) inflammation in which there is loss of muscle with or without loss of fat mass. In particular, it should be emphasized that nutritional frailty as a sole cause of weight loss is less common than sarcopenia (although the two can overlap) and that both nutritional frailty and sarcopenia can occur in the absence or presence of cachexia (again, see Fig. 9.1). It should be noted that the consensus definition for cachexia shown in Table 9.1 was recently developed by an International Cachexia Consensus group(1).
Fig. 9.1. The Unhappy Triad. Three distinct causes of weight loss and physical frailty have different prevalences and overlap to varying degrees. While sarcopenia occurs very commonly with aging, cachexia occurs mainly in association with acute or chronic disease. Weight loss due strictly to undereating is the least common of the three but has obvious overlap with the other causes of frailty. This conceptual presentation was originally proposed by Dr. Thomas at the Third Cachexia Consensus Conference in Rome, Italy, in December, 2005. It was derived from a paper published by Dr. Thomas on ‘‘Distinguishing Starvation from Cachexia’’(81). Dr. C.C.
Seiber assigned the figure the name of ‘‘The Unhappy Triad’’.
158 Bales and Ritchie
9.1.2. The Mortality Impact of Body Weight and Weight Loss
It might seem very obvious that decrements in food intake that result in under- nutrition and weight loss would adversely impact health. In the case of pronounced weight loss and subnormal body weights (expressed as a low Body Mass Index, calculated as weight (kg)/[height (m)]2; BMI), this is surely known to be the case.
Less well understood, however, are the complex interactions that occur between health and body mass when BMIs are within the range of normal to overweight (BMI 25–29.9 kg/m2). Recent concerns about the effects of the obesity epidemic on the health of adults of all ages(7,8) have raised the consciousness of both older patients and their caregivers regarding the potential detrimental effects of excess body weight. It is true that obesity in old age contributes to disability and frailty (9); it can also intensify metabolic disorders like insulin resistance and dyslipide- mias. However, the ideal BMI for older adults remains elusive. Epidemiological studies of the relationship of BMI with mortality reveal that the extent of the negative impact of being overweight tends to decline with aging(10,11). In fact, most studies show a beneficial or neutral, rather than a detrimental, effect of a BMI in the overweight range on length of life after the age of 65 years. Additionally, there Table 9.1
Glossary of weight-loss-related definitions
Nutritional frailty (weight loss due to undernutrition):An unintentional, precipitous decrease in body mass (both adipose and lean) that produces detrimental effects on function and other health outcomes and results almost entirely from a reduction in the intake of energy yielding nutrients. Nutritional frailty is distinct from age-related muscle loss (sarcopenia) and can occur in the absence or presence of cachexia.
Frailty:The presence of three or more of the following: unintentional weight loss, self- reported exhaustion, weakness, slow gait speed, and low physical activity(83).
Sarcopenia:The process of age-related loss of muscle mass and strength that occurs with aging; often the term sarcopenia is used to refer to older persons with skeletal muscle values in an unhealthy range, which has traditionally been defined as a height- adjusted muscle mass of#2 standard deviations below the mean of a young and healthy population; see Chapter 10.
Cachexia:‘‘Cachexia is a complex metabolic syndrome associated with underlying illness and characterized by loss of muscle with or without loss of fat mass. The prominent clinical feature of cachexia is weight loss in adults (corrected for fluid retention) or growth failure in children (excluding endocrine disorders). Anorexia, inflammation, insulin resistance and increased muscle protein breakdown are frequently associated with wasting disease. Wasting disease is distinct from
starvation, age-related loss of muscle mass, primary depression, malabsorption and hyperthyroidism and is associated with increased morbidity.’’ (Source: International Consensus Conference(1)); also see Chapter 11.
Sarcopenic obesity:Individuals with sarcopenia (defined above) who also have a percent body fat greater than sex-specific cutoff values and an approximate BMI of#30 kg/
m2(19).
Chapter 9/ Redefining Nutritional Frailty 159
is a well-established link between unintentional weight loss and poor health out- comes in later life. A number of studies have associated recent weight loss with shortened survival. Newman et al.(12)found that even a modest decline in body weight was an important, independent marker of risk for mortality in older adults.
Locher et al.(13)demonstrated a 1.7-fold increase in mortality risk with uninten- tional weight loss in community-dwelling older persons. A prospective study of weight loss and non-cancer-related mortality in 5,722 overweight/obese but other- wise healthy Swedish men showed that those who lost weight had higher mortality rates than weight stable men in the same weight range(14). Lee and Paffenberger (15) reviewed 17 studies of weight loss and subsequent all-cause mortality and concluded that those who ‘‘faired best’’ were those who remained weight stable.
The observation of increased survival in heavier adults with wasting diseases like end-stage renal disease, heart failure, and COPD (the so-called ‘‘reverse epide- miology’’ of obesity and wasting diseases) is another factor that contributes to concerns about the best approach for managing body weight issues in late life (16). Excess adiposity in late life can serve as an energy reserve in times of food deprivation or illness; additionally, the proportion of energy expenditure derived from protein oxidation is lower and lean tissue is better preserved in persons with large fat stores(17).
Body composition changes that occur with weight loss may also explain the negative effect of weight loss on function in older adults (18). Changes in body composition (particularly muscle and bone) with aging can lead to undesirable effects that would not be apparent from a change in body weight alone. In fact, due to hormonal and other changes discussed in more detail in Chapter 10, even adults who remain weight stable have a shift in body composition in later life characterized by more fat and less muscle and bone. When the loss of lean mass is dramatic, an individual may be frail even with a normal or elevated BMI. Sarco- penic obesity is associated with functional decline, including the development of disabilities for Instrumental Activities of Daily Living (IADLs)(19).