proportion of those in institutions. Depression is more likely to manifest as reduced appetite and weight loss in the elderly than in younger adults and is an important cause of weight loss and undernutrition in this group. Undernutrition per se, particularly if it produces folate deficiency, may further worsen depression, thus setting up a vicious cycle. Treatment of depression is effective in producing weight gain and improving other nutritional indices.
Dementia may also contribute to reduced food intake in the elderly, with a nearly twofold increased risk of anorexia compared with non‐demented subjects,69 because individuals simply forget to eat. Up to 50% of institutionalized dementia patients have been reported to suffer from protein‐energy malnutrition.27 Behavioral and psychological symptoms of dementia (BPSD) include eating problems. Apraxia of swallowing, including pocketing and spitting, delayed swallowing, and recurrent aspiration are associated with disease progression. Reduction of taste and smell may play a significant role. Weight loss is present very early, and even precedes dementia, and may be a significant preclinical marker.70
Chronic diseases including chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), and chronic kidney disease (CKD) are associated with reduced appetite. Older adults with COPD are in a catabolic state due to increased whole‐body energy expenditure, and caloric intake was found to be inadequate for measured energy expenditure, which widens during severe acute exacerbations. Anorexia in COPD is also associated with nicotine use, opioid use for pain leading to early satiety, and gastrointestinal motility disorders.71
Loss of appetite occurs in over 40% of adults with end‐stage CHF.72 Generalized loss of lean, fat, and bone tissue occur. Cachetic CHF patients have raised plasma levels of norepinephrine, epinephrine, and cortisol, and they show high plasma renin activity and increased plasma aldosterone levels. Hypoxia may be the stimulus for increased TNF‐a production in CHF patients.73 TNF has a variety of effects, including induction of apoptosis, rearrangement of the cytoskeleton leading to increased permeability to albumin and water, leading to impairment of the endothelial function.73 Increased TNF leads to increased plasma concentrations of the hormone leptin, effects noted previously.74
Anorexia affects 30–40% of adult patients on maintenance hemodialysis; it is associated with greater hospitalization rates, decreased quality of life, and a fourfold increase in mortality.75 Uremic toxins including leptin, ghrelin, and neuropeptide Y, as well as altered amino acid pattern and inflammation, are involved.76 Studies have shown that injections of uremic ultrafiltrate lead to reduced ingestion of sucrose and mixed nutritional solution in normal rats, although the effect was not specific for one type of nutrient.77 Increased frequency of hemodialysis can improve appetite and food intake.76
Environment and social determinants of health
One of the social factors contributing to decreased food intake in the elderly is poverty, which is associated with an increased rate of hunger and food insecurity. Many older individuals have limited financial means, which makes it difficult to afford food of good nutritional quality. Community‐dwelling older women with lower neighbourhood socioeconomic status have been found to have a lower serum carotenoid concentration, correlated with higher mortality.8
Older people are more likely to live alone than young adults, with approximately 29.3% of non‐institutionalized older adults living alone.8 Social isolation and loneliness have been associated with decreased appetite and energy intake in the elderly. Elderly people tend to consume substantially more food (up to 50%) during a meal when eating in the company of friends than when eating alone. The simple measure of having older people eat in company rather than alone may be effective in increasing their energy intake. For institutionalized older adults, facilities fail to cater to ethnic food preferences, negatively affecting the desire for food.78 Assisted living facilities have less regulated food and nutrition services compared to long‐term care. The nature and quality of food are mostly unknown, and assisted living facilities do not seem to provide the preventative health and nutrition services needed by older adults.8
Iatrogenic impact
Older adults often utilize multiple prescription medications, a number of which can cause malabsorption of nutrients, dysguesia (related to the inhibition of the cytochrome P450 metabolism system), gastrointestinal symptoms (such as dry mouth and constipation), and loss of appetite.30,79 For example, digoxin and some forms of chemotherapy can cause nausea, vomiting, and loss of appetite. Other medications can deplete the body’s mineral stores; high doses of aluminium or magnesium hydroxide antacids deplete phosphate and potassium stores, which can lead to muscle weakness and anorexia; and penicillamine induces zinc depletion that can lead to the loss of taste acuity and decreased food intake. Prescription of a high‐fibre diet may lead to excess satiety.8 More than 250 prescribed medications alter taste, and many others affect smell.80 Overall, older adults often take multiple medications that increase the risk of drug interactions that can cause anorexia.
Conclusion
Anorexia of ageing is associated with impaired muscle function, decreased bone mass, immune dysfunction, anaemia, reduced cognitive function, poor wound healing, delayed recovery from surgery, and ultimately increased morbidity and mortality. Epidemiological studies have demonstrated that protein‐energy malnutrition is a strong independent predictor of mortality in elderly people, regardless of whether they live in the community or a nursing home, are patients in a hospital, or have been discharged from the hospital in the previous one to two years.16 The increased mortality rate in elderly people with protein‐energy malnutrition is further increased in the presence of other medical diseases, such as renal failure, cardiac failure, and cerebrovascular disease. Figure 13.3 illustrates the factors contributing to anorexia as discussed in this chapter.
Figure 13.3 Anorexia as a multifactorial geriatric syndrome with poor outcomes.
Diagnoses and treatment of undernutrition in older people are covered in Chapter 12, ‘Epidemiology of Nutrition and Ageing’, and Chapter 14, ‘Weight Loss’.
Key points
Food intake is less in the elderly than in young adults because of a physiological decrease in appetite: the anorexia of ageing. This predisposes them to the development of protein‐energy malnutrition, a common entity in older adults.
Several additional factors contribute to undernutrition, including physical and physiological changes, chronic disease, environment and other relevant social determinants of health, and iatrogenic causes such as polypharmacy.
Chronic diseases such as dementia, depression, chronic obstructive pulmonary disease, and congestive heart failure can lead to anorexia through various mechanisms.
Activity changes of hormones such as CCK, cytokines, and androgens have been implicated in appetite regulation and the anorexia of ageing.
References
1 1. Morley JE. Anorexia of aging: physiologic and pathologic. Am J Clin Nutr. 1997; 66(4):760–773.
2 2. Shen HC, Chen HF, Peng LN, et al. Impact of nutritional status on long‐term functional outcomes of post‐acute stroke patients in Taiwan. Arch Gerontol Geriatr. 2011; 53(2):e149–152.
3 3.