Age-related physiological reduction in appetite, 'anorexia of aging,' is well documented. Several factors have been implicated in the genesis of this phenomenon. Evidence suggests that the decrease in lean body mass, energy expenditure, and metabolic rate that occurs with advancing age may partially account for the reduction of food intake in healthy older persons. Age-related reduction in olfactory and gustatory receptor sensitivity may compromise the hedonic qualities of meals, further reducing the desire to eat. Similarly, age-related alterations in hormonal and neurotransmitter-mediated function may also play a role in suppressing food intake. Animal studies suggest that aging results in a reduction in the opioid feeding drive and an increase in the satiating effect of cholecystokinin. This may lead to the ingestion of smaller meals and prolonged periods of satiety between meals. More recently ghrelin, a hunger-inducing peptide hormone, has been shown to decrease with age. Similarly, older hypogonadal men have inappropriately high levels of leptin, a satiation-inducing peptide hormone.
The occurrence of a variety of pathological factors superimposed on the background of age-related physiological changes may further compromise nutritional status in the older adult (Table 1). Existing data suggest that as many as one-third of undernourished older persons suffer from untreated depression. Neuro-vegetative symptoms in depressed older persons often result in anorexia, social withdrawal, reduced motivation, and decreased activity, all of which can compromise nutritional intake. The use of appropriate antidepressants very often reverses these symptoms, resulting in an increase in food intake and restoration of adequate nutritional status. Choice of antidepressants is crucial in the management of depressed, older undernourished persons. The popularity of selective serotonin reuptake inhibitors in younger persons has led to their increasing use in the older population. However, in older persons the efficacy of such agents in improving mood may be marred by adverse gastrointestinal effects, such as nausea, vomiting, and diarrhea, which may further compromise nutritional status. Thus, where such agents are used, careful monitoring of nutritional status is mandatory. Mirtazapine is a useful anti-depressant that is unrelated to selective serotonin
Table 1 Common and uncommon causes of undernutrition in older persons
Reduced food intake
Anorexia Ill-fitting dentures Periodontal disease Oropharyngeal disease Orofacial dyskinesias
Behavioral disorders Increased nutrient metabolism
Hyperthyroidism Phaeochromocytoma Wandering, agitation Movement disorders Hemiballismus
Reduced nutrient utilization
Chronic inflammatory bowel disease
Chronic bronchitis, emphysema Cardiac failure Malignant disease Substance abuse reuptake inhibitors, tricyclics, or monoamine oxidase inhibitors (MAOI). Mirtazapine belongs to the piperazino-azepine group of compounds. Available evidence suggests that Mirtazapine has an additional orexigenic and anti-emetic effect, which may increase energy consumption. Electroconvulsive therapy is a viable option in depressed persons with severe anorexia. Evidence exists in support of the efficacy of this treatment modality in restoring appetite following failure of pharmacological agents.
Minor dysphoric changes may adversely affect nutritional status and warrant intervention. Over 30% of older community-dwelling persons live alone, usually as a result of bereavement or migration of younger family members. Meals are often eaten alone and the lack of social interaction during meal preparation and consumption can compromise the recreational and hedonic aspects of dining. Consequently, such elders are poorly motivated to prepare and eat meals. Particular attention should be paid to the recreational aspects of mealtimes, and older persons should be encouraged to socialize during meals. This can be accomplished in a variety of ways. Participation in dining clubs, where available, should be encouraged. Arrangements can also be made for older persons to dine at senior citizens' centers. Ambulant senior citizens should be encouraged to eat out, if this is preferred.
Effective nutritional intervention mandates due consideration of financial and socioeconomic factors. Approximately one-third of the older population live below the poverty line and many experience difficulty with the purchase of food items necessary to ensure a balanced diet. Inadequate transportation, limited mobility, and poorly accessible shopping facilities may be added limiting factors. Social and community agency services should be considered where relevant, and an attempt should be made to provide appropriate assistance.
A wide variety of prescribed drugs can cause anorexia, nausea, and other symptoms of gastrointestinal distress in older persons, rendering medication review an important component of nutritional management. Digoxin, theophylline, and nonstero-idal anti-inflammatory agents are frequent culprits in this regard. Enquiry must also be made into the use and tolerance of self-prescribed medication. Offending drugs, once identified, must be discontinued. Iatrogenesis also contributes to undernutrition by way of therapeutic diets. Low-cholesterol and low-salt diets are often prescribed to older persons on the basis of data extrapolated from younger persons. There is currently little evidence to suggest that these diets are of any benefit to older persons when used as primary prevention strategies. Available data actually indicate increased mortality in older adults with low-cholesterol levels. Evidence suggests that hypocholesterolemia may reflect increased cytokine expression in acutely ill and frail older adults. Thus, restrictive diets in older persons should be discouraged, as they often reduce palatability and consequently discourage food intake. Health professionals should also make enquiries regarding self-prescribed diets. Studies indicate that the older population is more susceptible to food fads and advertised commercial diets, which are often unbalanced and of dubious benefit. Prolonged ingestion of such diets can result in marked undernutrition.
A wide variety of medical illnesses require focused therapeutic intervention in order to maintain or restore adequate nutritional status. Degenerative and neurological diseases can significantly impair mobility and physical function. The use of adapted appliances and cutlery in such cases may improve manual dexterity and preserve the ability to self-feed. In older persons with severely impaired function, who are unable to cook, meal delivery services ('meals on wheels') may be an acceptable alternative to home-cooked meals. Tooth loss is another important risk factor for undernutrition. Periodontal disease and edentulism are highly prevalent among the geriatric population and can impair masticatory ability. Older persons who have lost teeth, experience pain on mastication, or receive inadequate dental care should be carefully screened and offered appropriate therapy. The use of dentures may improve food intake. However, where dentures are poorly tolerated, alteration in the consistency of meals is helpful. Dysphagia occurs commonly in older persons with degenerative and vascular neurological conditions such as dementia, Parkinsonism, and cerebrovascular disease. A bedside swallowing evaluation should be an integral component of nutritional evaluation, followed by a modified barium swallow with fluoroscopy in cases where significant dysphagia is identified. In most cases oral food intake will remain possible, with appropriate modifications regarding swallowing technique, feeding precautions, and food consistency.
Health professionals often wrongly assume that older adults possess adequate knowledge of basic dietetic practice and nutritional studies. There is evidence to suggest that the nutritional attitudes and knowledge of undernourished older persons may be inadequate, particularly with regard to food preparation. Dietary education and counseling are crucial components of nutritional intervention in undernourished older persons who retain the responsibility for preparing their own meals. Such counseling should be targeted towards identifying deficits in basic dietary knowledge and the correction of poor nutritional practices.
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