Anorexia of Aging: Page 2 of 4
Medical Causes of Anorexia of Aging
Various physical ailments—some of which are debilitating—and their respective treatments can depress appetite or cause problems that interfere with eating. Conditions such as chronic obstructive pulmonary disease (COPD), Parkinson’s disease, and arthritis cause inflammation and impair mobility.13 Older adults are also prone to gastrointestinal disorders or malabsorption problems,11 which can contribute to decreased food intake and unintentional weight loss, as can constipation and fecal impaction.4 Cognitive impairment can also lead to weight loss13; individuals affected by Alzheimer’s disease or dementia, for example, may experience loss of appetite or forget to eat.14 The aging body also undergoes many physiologic and pathologic changes that can inhibit desire for and enjoyment of food.
Sensory Perception of Food
Taste, smell, sight, and texture are essential components of food enjoyment.15 People whose senses of smell and taste are diminished tend to experience fewer food cravings and demonstrate less positive involvement with food to the point where they may even question the purpose of eating. Doty and colleagues16 found that >60% of study participants between 65 and 80 years of age and >80% of participants ≥80 years had impaired taste and smell compared with taste and smell sensitivity among participants ≤50 years.
Dysfunction in taste and smell among the aged is usually attributable to chemosensory loss, but it can also result from chronic disease, medication use, and PEM.17 More than 250 prescription medications alter taste,11 whereas other drugs affect smell. Changes in how the taste and smell of foods are perceived typically contribute to poor dietary choices, decreased appetite, and low nutrient intake.10,11
Older adults experience “an increase in the taste threshold, difficulty in recognizing taste mixtures, an increased perception of irritating tastes, and a decreased number of supertasters.”3 Many studies suggest that our threshold for detecting specific tastes (eg, sweet, salty, bitter) increases with age and that certain medications can reduce the number of functioning taste buds and decrease taste sensitivity.18 One study reported that elderly individuals who took a moderate number of medications were less able to detect certain tastes at average threshold levels.17 Studies comparing taste perception between younger and older adults found that the elderly participants rated a broad range of tastes as less intense. People with a diminished sense of smell also demonstrate less interest in food and eat less.6
Studies have shown that using additives to imbue foods with more flavor helps compensate for age-related chemosensory losses.11 One study found that adding natural flavors to regular foods increased food intake among older hospitalized patients by 13% to 26%.7 Serving foods with pleasant aromas, such as freshly baked bread, may also help stimulate appetite. In addition, residents may find food more appealing if it is familiar, recognizable (not mushed together), seasoned, and served at the correct temperature.5,7,15
Many LTC residents have illnesses that warrant restrictions on amounts of fat, sugar, and sodium, and they find their meals less satisfying.5 The American Dietetic Association (ADA) notes that “a strict, unappealing therapeutic diet is not beneficial unless it is actually consumed.”5 In Tag F325, CMS encourages diet liberalization and recommends facilities consider temporarily lifting dietary restrictions for residents who are losing weight, undernourished, or at risk because they are not eating properly.4 CMS cautions nursing homes to consider the resident’s preferences in meal planning and recognize his or her right to decline recommended dietary restrictions.
Delayed Stomach Emptying (Gastroparesis)
Older adults who have suppressed appetites due to earlier and prolonged satiation are more likely to eat smaller and fewer meals, which can lead to insufficient calorie intake and malnutrition. Delayed stomach emptying, or gastroparesis, can lead to early satiation and complaints of fullness early on during mealtime. Other symptoms of gastroparesis include postprandial vomiting, nausea, abdominal pain, weight loss, and nutritional deficiencies.19 A study by Di Francesco and associates8 observed elderly individuals for 4 hours after they consumed an 800-kcal meal and found that gastric emptying was delayed by more than 2 hours, satiety lasted longer, and hunger was suppressed throughout the observation period.
With age, there are changes in the gastrointestinal sensory function, which can lead to premature feelings of fullness in older adults.10 According to Morley,3 aging is associated with damage to the receptive relaxation of the gastric fundus, which results in more rapid antral filling, gastric distension, and prolonged satiation.Delayed stomach emptying appears to be a normal consequence of aging, involving “reduced sensitivity to gastrointestinal distension”10 and slower emptying rates.7 Distension of the stomach is a key indication to end the meal, however, because of impaired receptive relaxation, which results in rapid antral filling, older adults perceive satiation before they have consumed enough calories to satisfy their nutritional needs.3
The hormone cholecystokinin (CCK), which is secreted by the proximal bowel in response to satiation and helps mediate gastric emptying, may also play a role. Studies suggest that sensitivity to the effects of CCK increase with age6 and that older adults have higher levels of CCK.10 The increased level of circulating CCK, combined with increased sensitivity, may slow antral emptying.6
Gastroparesis is also associated with certain illnesses, such as type 2 diabetes, which is estimated to account for one-third of cases.20 One study reported that 88% of Parkinson’s patients had delayed gastric emptying of solids and 38% had delayed gastric emptying of liquids.21 Other causes include damage to the vagus nerve during esophageal or stomach surgery; scleroderma; pancreatitis; imbalances in potassium, calcium, or magnesium; certain medications, especially narcotics and anticholinergic agents; and thyroid disease.20
A gastric emptying study can be used to determine whether a patient is experiencing delayed stomach emptying.19,20 Negative results may indicate the need to look for physical obstruction, such as a tumor. The diet for a resident with gastroparesis should be low in fat and fiber, which delay the transit of food through the stomach, and contain soft foods in small portions.20 Promotility drugs and enteral nutrition are other options for consideration. When possible, the use of pain-relieving narcotics and anticholinergics in individuals with gastroparesis should be avoided.19,20
Other Physiologic Factors
In addition to CCK, several other hormones may contribute to unintentional weight loss. Leptin, a peptide hormone produced in adipose tissue, helps maintain energy balance. The amount of circulating leptin is directly related to the size of fat stores.6 Di Francesco and colleagues8 noted that “low leptin levels signal loss of body fat and a need for energy intake, while high leptin levels testify [to] the presence of adequate body fat and no need for further food intake.” Research suggests that older adults have higher levels of leptin than younger adults.10,22 As the proportion of body fat increases with age, leptin levels may also rise, signaling the body to eat less.
Insulin, a satiety hormone, is another regulator of glucose metabolism. Insulin increases appetite by enhancing leptin signaling to the hypothalamus and inhibiting secretion of ghrelin, a hormone that stimulates appetite.10 Some researchers have found no relationship between insulin levels and the anorexia of aging, however,concluding that higher insulin levels are a byproduct of insulin resistance and insulin resistance is a response to an increase in body adiposity, rather than an effect of aging.6 Further research is needed to clarify what role, if any, insulin plays in unintended weight loss.