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Undernutrition in the elderly: a problem on the rise

Susan Holmes
BSc(Hons) PhD SRN FRSH
Director of Research and Development/ Professor of Nursing
Faculty of Health
Canterbury Christ Church University College
Canterbury, Kent

Undernutrition arises for many reasons (Table 1). Social isolation, perhaps exacerbated by depression, visual impairment or hearing difficulty, means that many both live and eat alone; this may reduce food consumption and general wellbeing. Limited mobility and/or physical disability may cause difficulties with shopping or food preparation.

[[NIP08_table1_55]]

Cognitive impairment similarly increases nutritional risk,(6) as individuals may "forget" to eat, and mood changes can potentiate anorexia. Lowered responsiveness to internal hunger cues may lead to long periods without food.(7) Changes in economic status often decrease the variety and quantity of food purchased and consumed, contributing significantly to undernutrition.(8)
Alterations in body function may also limit consumption. Those with dental problems often have eating difficulties and are more likely to be underweight.(9,10) Many have poorly fitting dentures, so foods requiring aggressive chewing (such as meat, fruit and vegetables) may be avoided. Since oral discomfort is often accepted as part of "normal" ageing,(11) many fail to seek help even when eating becomes difficult or painful. 
Swallowing ability may be compromised by decreased salivation, reduced oesophageal motility, or neurological disorders. Xerostomia (dry mouth) is common and aggravated by fluid restriction, prescribed or self-imposed. Changes in taste buds and olfactory nerves affect taste recognition and discrimination, altering established food preferences.(12) Medications, such as diuretics, anticonvulsants and antidepressants, may exacerbate xerostomia and alter taste sensation; long-term therapy including four or more drugs increases the risk of undernutrition.(13) Some drugs may cause nausea or alter vitamin metabolism (such as anticonvulsants, digoxin and paracetamol).(14)
The combined effects of limited food, restricted dietary fibre/fluid, reduced physical activity, decreased intestinal muscle tone and polypharmacy (eg, analgesics and laxatives) cause constipation. Increased gastrointestinal (GI) residue causes flatulence and, like constipation, may inhibit eating. 
Other GI changes influence digestion and absorption. Hypochlorhydria decreases calcium and iron absorption, impairs protein digestion and permits bacterial overgrowth. The latter reduces bile salt function, causing fat malabsorption, reduced absorption of fat-soluble vitamins, diarrhoea and vitamin B12 deficiency, which, exacerbated by lack of the intrinsic factor, causes pernicious anaemia. Gall bladder disease may reduce bile secretion and, with pancreatic insufficiency, impair digestion.
Body composition changes and a decline in physical activity reduce energy expenditure and requirements, primarily reflecting loss of lean body mass (LBM) and an increase in body fat, whether or not individuals are overweight. These also contribute to impaired glucose tolerance; although this appears to be a "normal" accompaniment to ageing, it can create problems for some people. Weight loss may help obese individuals.
Illness may exacerbate such effects. When limited to periods of acute illness, nutritional deficits are overcome once "normal" eating resumes; however, recovery is slower, and if repeated illness occurs, nutritional status may gradually decline. Even minor illness precipitates undernutrition when nutritional status is marginal; the acutely ill are more likely to die when undernourished.(15) Chronic illness enhances poor nutrition and increases susceptibility to acute illness; conversely, poor nutrition affects recovery.(16) Surgical outcome is similarly influenced by nutritional status while also increasing nutritional demand.(17) Similarly, nutrient requirements may also be increased by "demented wandering", the increased respiratory effort associated with chest infection, fever and the muscle rigidity/tremor of Parkinson's disease (Table 2). Dietary adequacy must be evaluated - increasing the nutrient density of meals may be necessary to maintain nutritional intake.

[[NIP08_table2_56]]

Complications of undernutrition
Undernutrition affects many body functions, influences responses to disease/infection, and significantly reduces quality of life.(18) It influences both ageing processes and general health,(16) causing weight loss, depletion of subcutaneous fat, progressive muscle wasting, apathy and malaise. Concurrent chronic disease (eg, cardiovascular, pulmonary and neurological disorders) may potentiate inactivity and muscle loss.(19,20)
More specifically, undernutrition results in depressed immunity, increased infection, muscle fatigue and drug toxicity.(21) Respiratory function may be inhibited(22) and cardiac failure potentiated.(23) Affected individuals require 31% more GP appointments and 52% more inpatient episodes than the well-nourished.(24) Its clinical significance cannot be overemphasised. However, because of its insidious nature and the way that it mimics characteristics of ageing, deterioration in health may occur long before overt signs of undernutrition occur.(8) Distinguishing between age-related changes and those due to poor nutrition is a challenge for clinicians; nutritional screening is crucial in assessment of old people. However, although the value of screening for risk factors of disease is well-established, nutrition is rarely considered.(8)
Davies and Holdsworth highlighted risk factors that indicate vulnerability to nutritional decline (Table 3).(25) To these Lehmann added mental confusion, high alcohol consumption, chewing/swallowing difficulties, lack of sunlight, medication side-effects and poor nutritional knowledge.(26) However, the presence of a single risk factor does not necessarily indicate the need for intervention, but must be considered in relation to the general condition. Nutritional screening tools provide more specific information. Nutritional screening must include:

  • Current condition: height, weight and body mass index (BMI).
  • Changes in condition: recent changes in appetite or body weight.
  • Potential effects of disease and/or treatment on food intake and nutritional requirements. These are influenced by the metabolic response to illness (Table 2).

[[NIP08_table3_56]]

A range of screening tools is available. These include the Malnutrition Universal Screening Tool (MUST)(24) and the Mini-Nutritional Assessment (MNA),(27,28) both developed for use in older adults in different settings, including the community. They rely on unintended weight loss and BMI together with additional risk factors designed to identify individuals at high, moderate or low nutritional risk; both are simple and quick to use. The findings must, however, be interpreted alongside the patient's condition as no tool provides useful data if wrongly interpreted.
Regular screening enables care to be dynamic and responsive to patients' changing needs. When patients are identified as being at nutritional risk more detailed assessment is required. Referral to a dietitian is recommended. When further assessment is not currently indicated, regular monitoring helps to ensure that nutritional status is maintained.

Nutritional requirements
Vulnerable individuals must be offered appropriate dietary advice based on awareness of the nutritional needs of older people. This can be difficult to achieve due to the heterogeneity of this population, which reaches different stages of ageing at different ages; chronological age may not indicate either health or nutritional needs, both of which vary considerably. There are, however, certain common features that can be used to guide nutritional intervention.
Since both LBM and basal metabolic rate usually decline with age, energy requirements are also reduced (Table 4). The nutrient density of meals must be increased to maintain nutrient intake.

[[NIP08_table4_57]]
 
Intake and body stores of many vitamins may be compromised as vitamin absorption is decreased by hypochlorhydria, particularly vitamins B6, B12 and folic acid; vitamin B2 intake falls with decreasing dairy intake. Vitamin D deficiency often accompanies reduced exposure to sunlight. Restricted dietary variety means that many consume inadequate vitamins and minerals; multivitamin and mineral supplementation may be needed.
 
Conclusion
If health is defined as the ability to function and live independently then most older adults are "healthy". However, health is relative and cannot always be equated with freedom from disease; many of those over 65 years have at least one chronic condition, even though most carry normal roles in the community. They are, however, exposed to many factors that may impact on nutritional status leading to ill-health and disability. Conversely, illness and disability can interfere with nutritional status, thus creating a vicious circle; many old people may be living with subclinical malnutrition although they demonstrate no overt signs of deficiency.(8)
The clinical significance of undernutrition is far greater than its incidence may suggest, yet it is almost always amenable to treatment. However, like many disorders of old age, undernutrition is difficult to detect. While there is little doubt that more research is needed, socioeconomic factors are also important; significant improvements could be made with relatively little expenditure - just thought and proactive behaviours. It is for that reason that nutritional screening and assessment are central to the history taking and physical examination of all older patients wherever they are located.(29)

References

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  31. Taylor S, McLaren S. Nutrition support: a team approach. London: Mosby; 1992.
  32. Department of Health. Dietary reference values for food energy and nutrients for the United Kingdom. Report on Health and Social Subjects 41. London: HMSO; 2001.

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