Anorexia of Aging
Anorexia of aging is the decrease in appetite and/or food intake that occurs in late life and leads to inability to maintain normal body weight. The term “anorexia of aging” was coined to describe the reduction in appetite and/or food intake that occurs in late life (Landi et al. 2016).
The reduction of appetite and food intake in late life is one of the most common conditions that characterize the aging process. Anorexia of aging is the term coined to define this phenomenon. Anorexia of aging may have detrimental effects on health status and is associated with poorer quality of life, reduced ability to cope with environmental stressors, increased morbidity (and reduced ability to recover from illnesses), and greater risk of dying from any causes. Anorexia of aging has multiple causes, including health problems associated with aging (oral/dental issues, gastrointestinal problems), acute or chronic diseases, socioeconomical circumstances (living alone, poverty), psychological factors (depression), and use of multiple medicaments (Landi et al. 2016). Routine and comprehensive evaluation of the nutritional status is necessary to identify older persons at risk of developing anorexia at early stages, when intervention may have more chances of success. Interventions targeting multiple causal factors and tailored to the single person’s needs are vital to prevent and/or treat anorexia of aging.
Key Research Findings
One of the famous aphorisms by Hippocrates states that “It augurs well, if the patient’s mind is sound, and he accepts all food that’s offered him; but, if the contrary conditions do prevail, the chances of recovery are slim” (Scholtz 1940, p. 272). This, as well as other ancient “medical mottos,” though mostly anecdotic, highlights that good appetite has always been considered to be a positive indicator of health status and one of the best predictors of recovery from diseases. This seems to be especially true for older people, since the combination of appetite loss and reduced food intake may render older persons more vulnerable to diseases and other internal and/or external stressors (Landi et al. 2017). Both appetite and food intake change substantially over the life course. This leads to changes in the quantity (and quality) of energy supplied to the organism to perform all physiological activities. The age-related decrease in food intake and/or a mismatch between dietary calories ingested and energy demands can eventually lead to malnutrition, a disorder associated with a large number of negative consequences. These include loss of muscle mass and strength, reduced ability to perform the activities of daily living, longer hospital stays, loss of independence, disability, increased healthcare burden, and mortality (Dent et al. 2018; Kiesswetter et al. 2013; Landi et al. 2010).
Although it is widely acknowledged that nutritional assessment and counseling are crucial to preserve good health, especially in older persons, the adoption of nutritional evaluations as a routine component of geriatric assessment is often overlooked.
In this chapter, a short review on the multiple factors underlying anorexia of aging and the currently available tools for its assessment are presented. In addition, emerging strategies for its management are discussed.
Anorexia of Aging: Prevalence, Causes, and Risk Factors
Anorexia of aging is a condition commonly encountered in older persons. Its prevalence varies according to the settings, gender, and the presence of comorbidities (Donini et al. 2013). It is estimated that about 20% of older people suffer from anorexia, with higher prevalence rates among long-term care residents, hospitalized patients, and people with neurological and/or inflammatory conditions (Prell and Perner 2018; Dent et al. 2018).
The causes of anorexia of aging are multiple and include both peripheral and central factors as well as processes that may co-occur in older persons (Wysokiński et al. 2015; Landi et al. 2017; Dent et al. 2018). The age-related deterioration in sight, smell, and taste may play a role in the development of anorexia of aging (Sanford 2017). This aspect, often considered an unavoidable consequence of aging, manifests after the age of 50 and contributes to reduced perception of food palatability.
Several hormonal changes occur with age that may modulate the function and activity of brain circuits responsible for appetite/satiety regulation (Dent et al. 2018; Landi et al. 2017; Wysokiński et al. 2015). In particular, perturbations in circulating levels of gastrointestinal mediators such as the anorexigenic cholecystokinin [CCK] and peptide tyrosine tyrosine (PYY), glucagon-like peptide 1 (GLP1), gastric inhibitory polypeptide (GIP), and the reduced secretion of the “hunger hormone” ghrelin by the gastrointestinal mucosa, may influence dietary attitudes and behaviors. Further to this, ghrelin release is negatively regulated by leptin and insulin, the levels of which may be increased in older adults due to central and peripheral resistance to these hormones (Soenen and Chapman 2013; Dent et al. 2018; Landi et al. 2017; Wysokiński et al. 2015).
At the gastric level, aging is associated with loss of fine-tuning of appetite-related mechanisms (Sturm et al. 2004). Gastrointestinal physiology is altered. In particular, both muscular tone and motility decrease. Gastric emptying is delayed and longer-lasting satiety occurs due to the decline of visceral neuron activity and altered distension of fundus and antrum (the mechanism that mediates the postprandial reduction of appetite) (Sturm et al. 2004). As a consequence, older people may experience reducing food desire and constipation. In addition, diminished stomach digestive ability may further negatively affect appetite and food intake in old age.
One of the hallmarks of the aging process is the presence of chronic low-grade inflammation. This involves higher circulating levels of proinflammatory cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor-α that may act both at central and peripheral level to reduce appetite (Laviano et al. 2005; Yeh et al. 2008). At the gastrointestinal level, these mediators reduce gastric emptying and intestinal motility. At the central level, inflammatory cytokines act on the hypothalamus and other brain areas that control appetite, conveying anorexigenic signals (Laviano et al. 2005; Yeh et al. 2008). In the context of central regulation of feeding, multiple monoamines such as serotonin and norepinephrine and several neuropeptides (i.e., neuropeptide Y, melanocortin, and corticotrophin-releasing factor) may play a relevant role in modulating several aspects of appetite (Morley 2015, 2017). During aging and in the setting of age-related disease conditions, perturbations in these mediators have been reported that may contribute to anorexia of aging (Morley 2015, 2017).
In almost all physiological systems, cellular processes follow some sort of fluctuations over the day (Chaudhari et al. 2017). This 24-h rhythmicity, mediated by intracellular circadian clocks, is altered during aging (Hood and Amir 2017). Circadian disruption significantly perturbs many physiological processes and might contribute to the development of alterations in feeding behaviors (Chaudhari et al. 2017). For instance, the appetite-suppressant leptin show circadian rhythms and circadian dysfunction has been linked to leptin resistance (Kettner et al. 2015), a possible contributor to anorexia of aging.
Another factor that is receiving increasing interest is the possible role played by gut microbiota in appetite regulation (Salazar et al. 2017). The microorganisms residing in the gastrointestinal tract may indeed influence a vast array of body systems and processes involved in food intake regulation. In particular, a bidirectional gut-brain axis exists, through which the gut microbes may influence host gut function, metabolism, immune system, and hormones (Postler and Ghosh 2017; Calvani et al. 2018). Major changes in gut microbiota occurs with aging (i.e., a shift in taxonomic composition and a decrease in microbial richness and diversity) and these changes were associated with worsening in physical function and malnutrition scores (Haran et al. 2018; Jackson et al. 2016).
Aging process is characterized by the increased risk of developing multiple diseases. The presence of multiple pathologies may directly or indirectly impact on nutritional status. Both chronic and acute diseases alter appetite, increase proinflammatory load, may induce malabsorption and/or increase the energy needs of the organism. For instance, this is the case of acute and chronic inflammatory diseases, hyperthyroidism, chronic obstructive pulmonary, cancer, advanced heart failure, gastrointestinal diseases with or without malabsorption syndromes. All these conditions are highly prevalent in older persons and may lead to loss of appetite, reduced food intake, and micro- and macronutrient deficiencies (Landi et al. 2017; Morley 2013).
Numerous diseases lead unavoidably to the consumption of several medications. Numerous prescribed drugs as well as over-the-counter medications taken by older adults may have deleterious effects on appetite, food intake, and overall nutritional status (Fávaro-Moreira et al. 2016). One of the best known examples of drug-food intake interactions is of course cancer chemotherapeutics that frequently cause nausea, vomiting, and loss of appetite. Penicillamine, used to treat rheumatoid arthritis, reduces zinc bioavailability leading to taste disturbances, while high doses of antacids (such as aluminum hydroxide and calcium carbonate) may cause several gastrointestinal disturbances (including nausea, vomiting, and anorexia) especially in older people.
Aging is associated with the presence of several forms of functional impairment, including physical limitations and mobility problems that lead to reduced ability to perform the activities of daily living related to food consumption (e.g., getting foods, cooking, eating independently) (Landi et al. 2010, 2013). In this context, also the abovementioned sensory impairment (such as hearing and vision loss) may further affect functional abilities of older people, thus limiting their daily food and energy supply.
Other factors, such as poor oral health (i.e., poor dentition, poor-fitting prosthesis, and inflammatory states of the oral cavity) and problems with chewing and swallowing may limit food choices and worsen the already poor food intake of older persons (Landi et al. 2017). Other social and economic conditions, such as living alone and poverty, contribute to the development of anorexia of aging, although new evidence suggested that malnutrition may affect older adults regardless of their socioeconomic group (Hoogendijk et al. 2018).
Finally, psychological factors such as depression negatively affect the amount and/or the types of food consumed (Dent 2017). Recently, a selective eating disorder, termed Avoidant/Restrictive Food Intake Disorder (AFRID), has been recognized by the American Psychiatric Association and included in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) (Dent 2017). Older adults with AFRID limit or avoid the consumption of specific foods because of several issues, for instance, fear of choking. The dissection of all the previously mentioned factors is crucial for the assessment and the management of anorexia of aging, as well for the development and implementation of novel intervention strategies.
Assessment and Management of Anorexia of Aging
As outlined in the previous section, anorexia of aging is associated with several negative health outcomes and reduced quality of life. The early detection and management of its symptoms should represent a vital part of older persons’ care. The first and most commonly reported symptom of anorexia of aging is of course a reduction of appetite that can be followed by weight loss and more in general changes in body composition (e.g., muscle loss) (Landi et al. 2017).
Validated screening tools exist that help identify people at risk for anorexia at the earliest stages. These include the Simplified Nutritional Assessment Questionnaire (SNAQ) (Wilson et al. 2005) and the Functional Assessment of Anorexia and Cachexia Therapy (FAACT) questionnaire (Davis et al. 2009). SNAQ is a self- assessed screening tool based on four items (i.e., appetite estimation, fullness during a meal, food taste, and number of meals consumed) (Wilson et al. 2005). FAACT includes 12 questions that investigate more thoroughly anorexia-related symptoms and grade their severity (Davis et al. 2009). Other tools that can be used to screen for nutritional problems in older people include the Mini Nutritional Assessment Short Form (MNA-SF), the Malnutrition Universal Screening Tool (MUST), and the Malnutrition Screening Tool (MST) that incorporate questions about involuntary weight loss and/or loss of appetite (Power et al. 2018).
Once identified individuals at risk, personalized nutrition care pathway should be designed (Cederholm et al. 2017). As commonly reported for other aspects of older persons’ healthcare, comprehensive multistep assessment programs aimed at identifying and managing risk factors for anorexia of aging are the best option to handle it. For example, second- and third-generation geriatric assessment tools may be used to evaluate a vast array of clinical, psychological, social, economic, and environmental factors across different healthcare settings (Bernabei et al. 2008). Recently, a new function-driven model for the assessment of nutritional status in older persons has been developed (Engelheart and Brummer 2018). The proposed model includes four domains (i.e., physical function and capacity; health and somatic disorders; food and nutrition; and cognitive, affective, and sensory function) that bidirectionally interact with the nutritional status. Results from the comprehensive nutritional assessment tool adopted may then be used to develop a personalized nutritional care plan that represents the first line of intervention in older people with anorexia of aging.
Treatment Options for Anorexia of Aging
Once an individual is found at risk of anorexia of aging, the ideal management aims at removing all potentially reversible causative factors. For the intrinsic complexity of the condition, this represents a very challenging task. In milder cases, minor and timely modifications in feeding patterns and behaviors may be successful, while in more advanced cases even “aggressive” dietary changes may not be sufficient.
Prevention and early intervention are critical for anorexia of aging. Recent systematic reviews have highlighted that nutritional intervention in older adults rarely give the expected results on major clinical outcomes (such as body weight, muscle mass, physical function, complication rates, and mortality) (Beck et al. 2016; Feinberg et al. 2017). This is especially true if the intervention is started when people are already malnourished (Beck et al. 2016; Feinberg et al. 2017). Among the possible intervention strategies, food manipulation and/or supplementation, lifestyle modifications, social support, appropriate drug de-prescribing, and treatment of concomitant diseases are the most effective (Landi et al. 2017).
Food manipulation aims at optimizing the “enjoyment of eating,” adapting food texture, flavor and palatability to the persons’ preferences, increasing dietary variety, and providing feeding assistance as needed. Nutritional interventions, such as the adoption of a Mediterranean diet pattern, and a daily intake of at least 1.0 g of protein per kg of body weight have been proposed to improve depression or to preserve muscle mass and strength (Volkert et al. 2018). However, the heterogeneity of intervention protocols and study outcomes limits the applicability of the results of these clinical trials in daily practice.
Among lifestyle modifications, physical activity is beneficial against all of the hallmarks of aging, including anorexia of ageing (Garatachea et al. 2015). Physical activity is particularly useful in improving some of the major causal/risk factors for anorexia of aging, including depression, functional impairment, and social isolation (Garatachea et al. 2015). However, a recent systematic review investigating the relationship between physical activity, appetite, and energy intake in older adults showed that there is currently limited evidence supporting the role of physical activity in increasing appetite in older adults (Clegg and Godfrey 2018).
Promotion of conviviality, especially in institutionalized older persons, represents another relevant action to pursue. A thorough revision of pharmacologic therapies is of utmost importance, given the deleterious effects of polypharmacy on appetite and food intake (Landi et al. 2016). As reported in the previous section, several age-related diseases and clinical correlates may induce appetite loss and reduced food intake (Landi et al. 2017). In particular, special attention should be focused on swallowing disorders, dysphagia, dyspepsia, malabsorption syndromes, neurologic and psychiatric disorders, chronic respiratory conditions, and endocrinologic and cardiovascular diseases (Landi et al. 2017).
Several therapeutic agents have been tested for treating anorexia of aging. However, none of them gave results that may support their use in clinical practice (Landi et al. 2017). Steroids (e.g., corticosteroids, testosterone) may induce gains in body weight but side effects offset benefits. The same limitations affect the prokinetic agent metoclopramide that, while improving early satiety in some persons, is associated with parkinsonian symptoms (slow movements, tremor, difficulty with walking and balance, stiffness, and rigidity) with long-term use. Other appetite-stimulating drugs, including megestrol, mirtazapine, and cyproheptadine, have been associated with relevant side effects, such as gastrointestinal symptoms and delirium (Landi et al. 2016).
In conclusion, the complex and multifaceted pathophysiology of the anorexia of aging implies the adoption of multicomponent approaches addressing simultaneously as many causes/risk factors as possible. This requires the presence of multidisciplinary teams (including clinicians, nutritionist, speech therapist, physical therapist, and psychologist) with complementary skills, which represents another challenging issue for the development of effective approach against the anorexia of aging.
Future Directions of Research
The investigation of novel emerging factors, including circadian clock and gut microbiota, may add new pieces into the complex puzzle of anorexia of aging. Personalized approaches may take advantage from the use of novel technologies (including analytical platforms able to measure multiple molecules from single blood drops) to predict health status trajectories. Novel foods and/or supplements are under development to help improve the quality of life and global health status of older people suffering from anorexia.
Anorexia of aging is one of the most burdensome problems experienced by older people. It deeply affects several aspects of an older person’s life, spanning from physical function to psychological wellbeing, and impacts on quality of life. Since anorexia of aging has multiple causes and develops over time, only a routine and comprehensive evaluation of its potential cause/risk factors by an interdisciplinary team may identify older persons at risk at early stages, when intervention have more chances to succeed. In the absence of effective antianorectic drugs, multicomponent interventions tailored to the single person’s needs currently represent the only available option to ensure the provision of adequate amounts of food to older persons.
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