Minimizing frailty in older age is important to individuals and society, as the increasing prevalence of chronic disease is leading to greater disability and health care costs. Nutritional frailty can be defined as the disability that occurs in old age due to rapid, unintentional loss of body weight and sarcopenia (lack of lean mass). This article provides a brief overview of the prevalence and consequences of undernutrition, age-related changes to appetite, food intake, and body composition, the factors contributing to the development of anorexia and undernutrition, and recommended management strategies.
As populations age, health policies and research agendas are focusing increasingly on healthy aging. Minimizing frailty in older age is important to individuals and society, as the increasing prevalence of chronic disease is leading to greater disability and health care costs. Widely used frailty scores, such as the Fried Frailty Score and the Rockwood Frailty Index, include weight loss among their parameters, which indicates the importance of healthy nutrition in the attainment of healthy aging. In keeping with this notion, a recent study found that low nutrient intake was independently associated with frailty. Nutritional frailty can be defined as the disability that occurs in old age due to rapid, unintentional loss of body weight and sarcopenia (lack of lean mass). A better understanding of the pathophysiology of undernutrition in older people is necessary to aid the development of effective prevention and intervention strategies, and achievement of healthy aging. This article provides a brief overview of the prevalence and consequences of undernutrition, age-related changes to appetite, food intake, and body composition, factors contributing to the development of anorexia and undernutrition, and recommended management strategies. Although malnutrition includes obesity, this topic is only briefly discussed in the context of older people in this article.
Prevalence of undernutrition
Prevalence figures for undernutrition among older people quoted in the literature vary depending on the assessment method used. There are multiple ways of assessing nutrition and undernutrition in older people, none of them universally accepted. To enable comparisons across different settings, prevalence figures quoted here are nutritional risk as assessed by the widely used Mini Nutritional Assessment (MNA; discussed later). The reported prevalence of nutritional risk in older people is approximately 45% in the community, 45% to 51% in domiciliary care settings, 50% to 82% in hospitals, and between 84% and 100% in residential care facilities. There is clearly a relationship between increasing frailty and increasing nutritional risk.
Adverse consequences of undernutrition
Undernutrition in older people is associated with multiple adverse health consequences, including impaired muscle function, decreased bone mass, immune dysfunction, anemia, reduced cognitive function, poor wound healing, delayed recovery from surgery, and ultimately, increased mortality. In the SENECA (Survey in Europe on Nutrition and the Elderly, a Concerted Action) study, subjects with better MNA scores (MNA ≥24) had significantly lower mortality (odds ratio: 0.35, 95% CI: 0.18–0.66) than subjects at nutritional risk (MNA <24). Older people often perceive entry into residential care as a bad outcome; individuals are at significant risk of this following an acute illness. Acute illness (inflammation) and prolonged bed rest results in increased protein catabolism, muscle loss, and loss of physical function. In one study of 908 community-dwelling elderly hospitalized patients, elderly malnourished subjects were 3 times more likely than nourished subjects to be subsequently institutionalized (20.3% MNA <17 versus 7.7% MNA ≥24; P <.001). A study by the authors’ group also confirmed that undernourished (MNA <24) community-dwelling older people in receipt of domiciliary care services were more likely to be hospitalized and spend longer in hospital than their nourished counterparts. Individuals experiencing poor nutritional health are clearly at a higher risk of adverse health outcomes, increased frailty, and reduced quality of life.
Adverse consequences of undernutrition
Undernutrition in older people is associated with multiple adverse health consequences, including impaired muscle function, decreased bone mass, immune dysfunction, anemia, reduced cognitive function, poor wound healing, delayed recovery from surgery, and ultimately, increased mortality. In the SENECA (Survey in Europe on Nutrition and the Elderly, a Concerted Action) study, subjects with better MNA scores (MNA ≥24) had significantly lower mortality (odds ratio: 0.35, 95% CI: 0.18–0.66) than subjects at nutritional risk (MNA <24). Older people often perceive entry into residential care as a bad outcome; individuals are at significant risk of this following an acute illness. Acute illness (inflammation) and prolonged bed rest results in increased protein catabolism, muscle loss, and loss of physical function. In one study of 908 community-dwelling elderly hospitalized patients, elderly malnourished subjects were 3 times more likely than nourished subjects to be subsequently institutionalized (20.3% MNA <17 versus 7.7% MNA ≥24; P <.001). A study by the authors’ group also confirmed that undernourished (MNA <24) community-dwelling older people in receipt of domiciliary care services were more likely to be hospitalized and spend longer in hospital than their nourished counterparts. Individuals experiencing poor nutritional health are clearly at a higher risk of adverse health outcomes, increased frailty, and reduced quality of life.
Recognizing undernutrition
There is no generally accepted gold standard method for the diagnosis of undernutrition in older people. The MNA, the Malnutrition Universal Screening Tool, and the Subjective Global Assessment are commonly used screening tools. Common to most screening tools are questions about weight loss and the body mass index (BMI), calculated as the weight in kilograms divided by height in meters squared. Appetite reduction usually precedes weight loss. The Simplified Nutritional Appetite Questionnaire comprises four questions on appetite, timing of eating, and frequency of meals and taste, and has a high sensitivity and specificity (both >75%) in predicting future 5% weight loss in older people. The use of this tool in otherwise healthy older people can identify those who require assessment to prevent weight loss. Screening should be followed by a more in-depth assessment by experienced clinicians to confirm the diagnosis. A detailed assessment usually involves a combination of the following: anthropometric measures, questions regarding weight loss, food intake assessment, medication history, and measurement of blood parameters such as serum albumin, hematocrit, lymphocyte count, total cholesterol, and serum folate (all of which tend to be reduced in malnutrition). Although there is ongoing debate about the best screening tool to use, a greater challenge is to be aware of undernutrition in older people, so that the diagnosis is considered, some screening is undertaken, and assessment and intervention follow.
Weight Loss and Body Mass Index
On average, body weight and hence BMI increase through adult life until about age 50 to 60 years, after which they decline. One explanation for the decline in body weight after the age of 50 to 60 years detected in cross-sectional studies is the premature demise of obese individuals. This finding is a factor, but even in longitudinal studies there is evidence of a decrease in body weight from the age of 60 years onwards. In one prospective study of community-dwelling Americans, men aged 65 years and older lost on average 0.5% of their body weight per year and 13.1% of the group had weight loss of 4% or more per year. Because of this weight loss and the premature death of obese individuals, the prevalence of overweight and obesity declines after about age 65 years, whereas the prevalence of underweight increases. For instance in the 1997 to 1998 US National Health Interview Survey of 68,556 adults, more people aged 75 years and older than those 45 to 64 years old were “underweight” (BMI <18.5 kg/m 2 ; 5 versus 1.6%) and substantially fewer were “overweight” (BMI >25 kg/m 2 ; 61.1 versus 47.2%).
Clinicians must look out for weight loss in older people, as it occurs commonly, and whether unintentional or intentional (probable) weight loss is associated with poor outcomes (see Omran and Morley for review). For example, the Cardiovascular Health Study in the United States prospectively evaluated 4714 home-dwelling subjects without cancer aged 65 years and older. By 3 years, 17% of the subjects had lost 5% or more of their initial body weight. During the next 4 years this group had significantly greater total (2.09×↑ [95% CI 1.67–2.62]) and risk-adjusted mortality (1.67×↑ [1.29–2.15]) than the stable weight group. This increased risk occurred irrespective of the starting weight and apparently irrespective of whether weight was lost intentionally or not. Similar results were seen in the Systolic Hypertension in the Elderly Program (SHEP) study, in which subjects who lost 1.6 kg/y or more had a 4.9 times greater death rate (95% CI 3.5–6.8) than those without significant weight change. The association between increased mortality and weight loss was present even in the subjects who were heaviest at baseline (BMI ≥31) and was independent of baseline weight. Subjects with a low baseline weight (BMI < 23.6 kg/m 2 ) who lost more than 1.6 kg/y had a mortality rate of 22.6%, almost 20 times greater than the mortality rate of those with a baseline BMI of 23.6 to 28 kg/m 2 whose weight remained stable. Therefore, weight loss in an older person of initially low body weight is associated with a particularly bad outcome. This situation perhaps occurs because such weight loss is occurring in individuals who are already sarcopenic or because this weight loss is a reflection of underlying disease or inflammation, and therefore more likely to be unintentional. The tendency for older people to lose weight is variable, with lean individuals probably most at risk. In keeping with this tendency, underweight older individuals irrespective of current weight stability should be comprehensively evaluated to minimize factors that may contribute to weight loss and poor nutritional health.
It is uncertain whether intentional weight loss really does result in adverse health outcomes in older people. There are epidemiologic studies to suggest this. The issue is especially important when advising older, overweight people about whether they should attempt to lose weight. Obesity is now a common health condition in older people and is increasing in prevalence. Obesity in older people is associated with increased disability, particularly from lower limb arthritis. In the English Longitudinal Study of Ageing (ELSA), 3793 individuals aged 65 years and older had BMI measured and were followed for a mean of 5 years 1 month. In this study, obese men and women had increased relative risks of reporting difficulties with their activities of daily living (men: relative risk [RR] 1.99, 95% CI 1.42–2.78; women: RR 1.66, 95% CI 1.25–2.19) and having impaired physical function (men: RR 1.51, 95% CI 1.05–2.16; women: RR 1.51, 95% CI 1.14–2.00) in comparison to individuals with BMI between 20 and 24.9 kg/m 2 (reference group). This risk increased between 1.5 and 2 times in severely obese (BMI ≥35 kg/m 2 ) individuals. There is evidence that weight loss in overweight older people is associated with improved quality of life. In the Nurses Health Study weight loss in initially overweight women was associated with improved physical function and vitality as well as decreased bodily pain. Therefore older, overweight people will often, appropriately, want to lose weight. When weight is lost, however, there is a propensity to lose lean tissue as well as fat. The loss of this lean tissue, mainly muscle and bone, has several adverse effects in older people. Even when weight is regained, the gain in lean mass does not make up for the loss during the weight-loss period. Therefore, advice to older people to lose weight should be given cautiously and only to achieve a specific goal (eg, better mobility). Ideally the weight loss should be achieved in a way that preserves lean tissue as much as possible, by including an exercise component and optimizing bone protection with adequate calcium and vitamin D intake. Villareal et al have shown that weight can be lost with preservation of muscle mass in obese, older people, with a 6-month program of behavioral therapy in conjunction with exercise training three times per week.
The evidence that deliberate weight loss by overweight, older people prolongs their lives is weaker. For example, in the ELSA study individuals with BMI between 30 and 35 kg/m 2 did not have increased mortality risk compared with the reference group. An increase in mortality risk was only seen for men with morbid obesity (BMI ≥35 kg/m 2 ). Even after excluding from that study individuals with large weight loss (5% or greater), with baseline disability, who smoked, with poor or fair baseline health, and with one or more comorbidities at baseline, there was no association between mortality and weight except in the most obese. This lack of association in older people has been reported in many other studies. In terms of mortality and obese older individuals, the findings in various studies have been variable with a recent systematic review concluding that there is only a modest (about 10%) increase in mortality risk. In the setting of chronic disease, obese individuals have a better prognosis than those with the ideal weight and this phenomenon has been described as the “obesity paradox.” It may be that those individuals with chronic disease and a higher BMI are protected by having less inflammation and more lean mass. Perhaps obese individuals seek treatment sooner and therefore have better prognosis. There may also be a selection bias in that more susceptible obese individuals may have died before study enrollment, and those remaining to participate in studies are more robust and have some sort of protective factors.
The distribution of adipose tissue is believed to be more important than the actual amount of fat tissue, and it is therefore not surprising that there are conflicting results in relation to mortality when the less accurate surrogate measure of BMI is used. The BMI or body weight does not allow clinicians to account for the relative amounts and differing effects of lean and fat mass. In the British Regional Heart Study, 4107 men (age 60–79 years) were reexamined in their 20th year of follow-up. Mean follow-up from the time of reexamination was 6 years with a total of 713 deaths during this time. Men with underweight BMI (<18.5 kg/m 2 ) had the highest mortality but those who were overweight or obese had no increased risk of mortality in comparison to the ideal weight (18.5–24.9 kg/m 2 ) group after adjusting for indicators of ill health predictive of mortality. In this study, even after adjusting for BMI and mid arm circumference (MAC) there was, however, a strong positive association seen between increasing waist circumference (WC) and mortality (WC >102 cm; RR 1.53, 95% CI 1.15–2.05). In this study the association between WC and waist to hip ratio and mortality risk became significant only following adjustment for lean mass as measured by MAC. Clearly a lack of muscle mass and increased abdominal adiposity is associated with increased mortality risk in older men. Those with the lowest mortality risk were those with low WC (≤102 cm) and medium (24.92–26.42 cm) to high (>26.42 cm) MAC. Individuals with low MAC irrespective of WC had increased mortality risk. Increased mortality risk was also seen in individuals with medium and high MAC and increased WC.
Pathophysiology of undernutrition
In general the reasons for undernutrition in older people are multiple and can broadly be categorized into age-related impairments of homeostasis, nonphysiologic causes, and physiologic causes such as sarcopenia and anorexia. These are discussed in subsequent sections.
Age-Related Impairment of Homeostasis
Healthy aging is associated with a physiologic decline in energy (food) intake and a reduction in function of homeostatic mechanisms that work in younger people to restore food intake in response to anorectic insults. As an illustration, Roberts and colleagues underfed young and old men by 3.17 MJ/d (≈750 kcal/d) for 21 days and this was accompanied by weight loss in the young and old. After the underfeeding period the men were allowed to again eat ad libitum. The young men ate more than at baseline (before underfeeding) and quickly returned to normal weight, whereas the old men did not compensate, returned only to their baseline intake, and did not regain the weight they had lost. The combination of age-related physiologic anorexia and impaired homeostasis means older people do not respond as well as young adults to acute undernutrition. In consequence, after an anorectic insult (for example, major surgery), older people are likely to take longer than young adults to regain the lost weight, remain undernourished longer, and be more susceptible to subsequent superimposed illnesses, such as infections. Without aggressive intervention, there is a predisposition to a spiral of decline toward increasing frailty.
Nonphysiologic Factors
Similar to other geriatric syndromes (ie, falls), there are numerous intrinsic and extrinsic nonphysiologic factors contributing to poor nutritional health in older people ( Box 1 ). These factors are frequently overlooked when attempting to manage undernutrition in older people, and this may be a major reason for treatment failure.
Intrinsic factors
Oral health
Mouth ulcers
Oral candida
Poor dentition
Gastrointestinal
Esophagitis
Esophageal stricture
Achalasia
Peptic ulcer disease/atrophic gastritis
Constipation
Colitis
Malabsorption
Neurologic
Dementia
Parkinson disease
Cerebrovascular disease
Psychological
Alcoholism
Bereavement
Depression
Cholesterol phobia
Endocrinology
Thyrotoxicosis
Hypothyroidism
Hypoadrenalism
Hyperparathyroidism
Other medical (cachexia)
Cardiac failure, chronic obstructive airways disease, renal failure
Inflammatory athropathies
Infection: HIV, malignancy
Extrinsic factors
Social factors
Poverty
Lack of transport
Inability to shop
Inability to prepare and cook meals
Inability to feed
Social isolation
Lack of social support
Failure to cater to ethnic/food preferences
Medications (this list is not exhaustive)
Nausea/vomiting : antibiotics, opiates, digoxin, theophylline, nonsteroidal anti-inflammatory drugs (NSAIDs)
Anorexia : antibiotics, digoxin
Hypogeusia : metronidazole, calcium channel blockers, angiotensin-converting enzyme inhibitors, metformin
Early satiety : anticholinergic drugs, sympathomimetic agents
Reduced feeding ability : sedatives, opiates, psychotropic agents
Dysphagia : potassium supplements, NSAIDs, biphosphonates, prednisolone
Constipation : opiates, iron supplements, diuretics
Diarrhea : laxatives, antibiotics
Hypermetabolism : thyroxin, ephedrine
Data from Chapman IM. Endocrinology of anorexia of ageing. Best Pract Res Clin Endocrinol Metab 2004;18:437–52. MacIntosh C, Morley JE, Chapman IM. The anorexia of aging. Nutrition 2000;16:983–5.
Sarcopenia
With increasing age there is loss of skeletal muscle mass, quality, and strength. Muscle cross-sectional area decreases by approximately 40% between the ages of 20 and 60 years and muscle strength is 20% to 40% lower in healthy men and women in their seventh and eighth decades than in their young adult counterparts. Not only are there altered central and peripheral nervous system innervations but also influences from other factors such as decreased physical activity, altered hormonal status, inflammation, and decreased caloric and protein intake. Inflammatory cytokines such as interleukin (IL)-6 are implicated in muscle mass loss (sarcopenia or cachexia), strength loss, and the development of disability. Tumor necrosis factor-α (TNF-α) and IL-1β stimulate the release of IL-6. One could also argue that reduced caloric and protein intake may in part be driven by the anorexia of aging, which is described subsequently. There have been informative reviews on this topic.
The progressive loss of skeletal muscle mass with increasing age, which can be up to 3 kg of lean body mass per decade after age 50 years, is accompanied by a progressive increase in fat tissue. Normal aging is associated with an increase in fat mass that peaks at approximately age 65 years in men and later in women. Therefore, on average, older people at any given weight have substantially more body fat than young adults, indeed approximately twice as much in 75-year-old men as in 20-year-old men of the same weight. Body fat is also distributed differently in older adults. A greater proportion of body fat in older than younger people is intrahepatic, intramuscular, and intra-abdominal versus subcutaneous, changes that in younger people are associated with increased insulin resistance and adverse metabolic outcomes. Given the increasing prevalence of obesity in middle-aged individuals, more people are entering old age with body fat stores already high. Coupled with the age-related loss of lean tissue, this means that sarcopenia and obesity (sarcopenic obesity) commonly coexist in older people. Sarcopenic obesity seems to be associated with worse health outcomes than sarcopenia or obesity alone. Current definitions of sarcopenic obesity are based on the amount of lean mass and fat mass in an individual, derived from body composition measurements. These measures, although useful, do not account for differences in the quality of the muscle tissue, muscle strength, and the distribution of the fat tissue. Assessment of these criteria may further enhance the prognostic significance or these measures.
The Physiologic Anorexia of Aging
Appetite loss
The “anorexia of aging” is a term used to refer to the physiologic reduction in appetite and food intake that accompanies normal aging. The appetite loss and reduced oral intake seen with increasing age often predates the development of weight loss and undernutrition. In comparison with younger people, healthy older people are less hungry and more full before meals, consume smaller and more monotonous meals more slowly, eat fewer snacks between meals, and become more rapidly satiated after eating a standard meal. Average daily energy intake has been reported to decrease by up to 30% between 20 and 80 years. For example, a decline in energy intake of 1321 calories/d in men and 629 calories/d in women between the ages and 20 and 80 years was reported in the 1989 cross-sectional American National Health and Nutrition Examination Survey, NHANES III. Much of the age-related decrease in energy is probably a response to the decline in energy expenditure that also occurs as people get older. In many individuals, however, the decrease in energy intake is greater than the decrease in energy expenditure, so body weight is lost.
Alteration to taste and smell
Taste and smell are important in making eating pleasurable. In animals, aging is associated with altered function of ion channels, and receptors result that mediate taste and changes to taste cell membranes. The sense of taste probably declines with age in humans but the results of studies are variable. The number of fibers in the olfactory bulb and the number of olfactory receptors decrease with age. With aging, increased receptor cell death is noted, whereas regeneration of olfactory receptor neurons is reduced. In consequence, after the age of 50 years the sense of smell deteriorates in humans. In one study, compared with only 10% of subjects younger than 50 years of age, more than 60% of subjects aged 65 to 80 years and more than 80% of subjects aged 80 years or older had major reductions in their sense of smell. The decline in sense of smell decreases food intake in the elderly and influences the type of food eaten, most likely resulting in a reduced interest in intake of food and a less varied, more monotonous diet. Sensory-specific satiety is the normal decline in pleasantness of the taste of a particular food after it has been consumed, resulting in a shift to other food choices during a meal and promoting the intake of a more varied, nutritionally balanced diet. The capacity to develop sensory-specific satiety is reduced in older people, perhaps due to reduced taste and smell, and this may contribute to a less varied diet and reduced energy intake in older people.
Gut mechanisms
Aging is associated with cell loss in the myenteric plexus of the human esophagus and a decline in conduction velocity within visceral neurons. The consequent reduction in sensory perception may contribute to reduced food intake by inhibiting the positive stimuli for feeding. The elderly frequently complain of increased fullness and early satiation during a meal. This complaint may also be related to changes in gastrointestinal sensory function; aging is associated with reduced sensitivity to gastrointestinal tract distension. If anything, reduced sensitivity to the satiating effects of distension might be expected to increase, not decrease, food intake in older people. Nevertheless, proximal gastric distension has been found to have similar effects on food intake in healthy older and young adults. Therefore the role, if any, of impairment of gastric sensory function in causing the anorexia of aging is unknown.
Aging is associated with a slowing of gastric emptying, which may relate to altered activity of nitric oxide (NO) and hence with the development of anorexia. Altered fundic NO results in an impaired gastric accommodation response. Peripheral NO causes receptive and adaptive relaxation of the stomach, leading to dilation of the fundus and ultimately slower gastric emptying. Clarkston and colleagues found that healthy older subjects were less hungry and more satiated after a meal than young subjects, and that postprandial hunger was inversely related to the rate of gastric emptying. When small meals are consumed, as is the case with most older people, the gastric emptying rate between young and old is not different. Delayed gastric emptying in older people, which is usually seen when meals with large energy content is consumed may, in part, result from enhanced release of small intestinal hormones such as cholecystokinin (CCK) (discussed later).
Gut transit time is not affected in healthy older people. Healthy older people do have slower phase III migration velocities and more frequent “propagated contractions” in the small intestine, but no differences in duration of postprandial motility or amplitude or frequency of fasting or postprandial pressure waves.
Neuroendocrine mechanisms
Appetite and food intake ( Table 1 ) are heavily influenced by actions of components of the neuroendocrine axis, including the opioids, noradrenaline, neuropeptide Y, the orexins, galanin, and ghrelin, and the inhibitory effect of corticotrophin-releasing factor, serotonin, CCK, and possibly insulin. A more detailed review is available elsewhere.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
