Decrease muscle mass (mainly measured by DXA or BIA)
Decreased gait speed (0.8 m/s) and/or decreased handgrip strength
An upcoming clinical challenge is the fast growing overweight or obese population, which is also often seen in older adults. Even if their body mass index may be high, this does not exclude that these persons suffer in parallel of a sarcopenia, with even worse consequences for functionality. This indeed unhealthy combination is called sarcopenic obesity . Even we understand more and more the pathophysiology behind sarcopenia, the diagnosis is still a matter of debate as the specific therapy . This entity may even be combined with osteoporosis, now called osteosarcopenia .
Frailty may be regarded as a geriatric syndrome of decreased reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems, causing vulnerability to adverse health outcomes including falls, hospitalization, institutionalization, and mortality. Concepts on the pathophysiological background of the frailty syndrome focus on inflammatory processes, hormonal changes, and body composition.
Nevertheless, some characteristics of frailty apply for normal aging like reduced physiologic reserve, decreased organ function and functional reserve, and loss of complexity. According to some authors, it might therefore not be possible to distinguish frailty unambiguously from advanced stages of the aging process.
The two most widely utilized approaches are the phenotypic definition of frailty developed by Fried and co-workers based on data from the Cardiovascular Health Survey  and the Frailty Index developed by Rockwood and co-workers . The Fried definition proposes five items: weight loss, exhaustion, weakness, slow walking speed, and low levels of physical activity . Frailty is diagnosed when at least three criteria are met. An individual is said to be pre-frail when one or two of these criteria are present.
A series of studies concentrated on the relationship between nutrition and frailty. It was shown that frailty is significantly associated with a daily energy intake below 21 kcal/kg body weight as well as a low protein intake . The simultaneous prevalence of more than one vitamin deficiency was also significantly higher for the pre-frail and frail individuals.
Based on the results of several recent studies, the criterion weight loss may be regarded as one-dimensional. Weight loss in an obese person may have different consequences—both for morbidity and mortality—as in normal or even underweight older adults. Furthermore, the weight loss thresholds given in the Fried criteria may be too high for a European population, as shown in a study in community-dwelling older persons .
For the calculation of the Frailty Index by Rockwood, it is necessary to count pre-specified deficits that are present in an individual [15, 18, 19]. In the most extensive study regarding this topic, Rockwood and co-workers have published yet 70 deficits that were used for the evaluation. These included active diseases, ability in the activities of daily living, and physical signs from the clinical and neurological examinations. The presence of a deficit scored 1. Theoretically, but not practically, a maximum score of 70 was possible. The Frailty Index is the score of present deficits divided by 70. The highest number of deficits the authors found in any setting was 47. Both the Fried and Rockwood Frailty criteria have recently been shown to be associated with incident disability and mortality in community-dwelling people and nursing home inhabitants.
Protein-energy malnutrition (PEM) has first been described as a severe clinical problem in the 1980s and 1990s with a fast increasing understanding of its pathophysiological background. Increasing research to tackle this problem came out of oncology, where cancer-associate PEM was strongly related to inflammatory processes (such as an increase in tumor necrosis factor-alpha). Even more importantly, it was and still is well known that this high inflammatory load renders nutritional treatment successes disappointing . Cachexia was then defined as disease-related loss of body cell mass, not necessarily linked with concurrent weight loss. In contrast, weight loss irrespective of the effects on body composition is termed wasting disorders, and the involuntary age-associated non-disease-related—e.g., age-specific—muscle loss was called sarcopenia.
21.2 Nutrition and Fluid Demands
21.2.1 Nutritional Demands
On average, an older adult needs 25–30 kcal per kilogram body weight per day. This may be increased in catabolic states (e.g., infection, pressure sores). In hyperactive dementia patients, the caloric needs may also be significantly increased.
Protein demands are also increased in frail older adults and surpass the WHO recommendations for younger healthy adults quite a bit. So, the usual recommended 0.8 grams of protein per kilogram body weight per day have to be increased to 1.0–1.2 grams per kilogram body weight per day . In the rehabilitation setting after longer catabolic periods, these demands may even go up to 1.5 proteins per kilogram body weight per day. Malnutrition in older adults after a hip fracture is indeed a bad prognostic factor “quoad”survival . Older adults still have a good anabolic capacity, but the proportion of protein intake and the body protein anabolism shows a faster ceiling effect. This is why the protein intake has to be distributed over the day, at least between the main meals . If this is not possible through a normal diet (even after fortification), the positive effects of oral supplements are well documented . It may well be that specific oral supplements for sarcopenic patients will not only increase muscle mass but also functionality, even without an additional physical exercise program, as recently shown .
Micronutrient needs are usually covered when usual diet is eaten. As a rule of thumb, micronutrient deficits can be expected if a person eats less than 1200 kcal per kilogram per day over a longer period, which may be in times of a severe acute illness and then subsequently a rehabilitation period of several weeks. It is only in these cases when micronutrients need to be replaced.
21.2.2 Fluid Demands
As an overall quantity, the daily fluid intake should be between 1500 and 2000 mL. Nevertheless, many older adults—especially women—never drank this quantity during their previous adult life. So, a personal “fluid intake biography” should always be performed. As thirst tends to decrease during the normal aging process, older adults should be informed about the importance of an adequate fluid intake and be stimulated to have a drink whenever possible.
Diuretics—especially hydrochlorothizide—are not only often prescribed for both systolic hypertension and peripheral edema but are also not reevaluated if still needed in the long course. This may, besides the often induced hyponatremia, aggravate exsiccosis in times when fluid intake is especially important as in hot summer days.
The danger of exsiccosis is also frequently not seen in its consequences such as the propensity to falls. In the acute setting, fluid restriction and exsiccosis are important risk factors for delirium, especially in patients with an existing cognitive deficit.
21.3 Assessment of Malnutrition and Fluid Intake
As an insufficient intake of both nutrients and fluid is very frequent in the acute and rehabilitation setting in older adults, therefore, intake of both components should be documented, starting from the first day of admission in the institution. In addition, a screening for risk or overt malnutrition should be performed early during the hospitalization phase.
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21.3.2 Mini Nutritional Assessment (MNAR) and Nutritional Risk Screening (NRS 2002)
The Mini Nutritional Assessment (MNAR) is the only screening and assessment test for malnutrition especially developed for an older person/patient group. There exists a full form as well as a short form (MNAR-SF), taking around 5 min to be performed  (freely available under www.mna-elderly.com). Its global practicability has been well documented and has even received much more use since when body mass index (BMI) is not available; it can be replaced by calf circumference (Table 21.2). Using this screening test, the highest prevalence for risk and overt malnutrition is found in the rehabilitation setting, pointing out how important especially nutrition is in this postacute period of older adults. If this screening test is positive, one needs to add an in-depth assessment for possible treatable causes of malnutrition.
The Mini Nutritional Assessment (MNAR-SF) 
This screening test consists of six items:
• Reduced nutritional intake within the last 3 months
• Loss of body weight within the last 3 months
• Reduced mobility within the last 3 months
• Acute disease or psychological stress within the last 3 months
• Neuropsychological problems (depression/dementia) within the last 3 months
• Actual BMI or calf circumference (CC <31 cm)
The Nutritional Risk Screening (NRS 2002) has been developed for the acute care setting and screens for those patients who will profit from a nutritional intervention during the hospital stay . Is also takes only a few minutes. Whereas the MNAR is more adapted for older adults, it may well be that patients are transferred from the acute care setting with a result of the NRS 2002, depending on local structures and preferences. This does not preclude that the MNAR can be performed shortly after the patient is admitted to the rehabilitation center, as the test includes in its six questions one question for mobility and one for mood changes (depression and/or dementia). Indeed, when comparing the two sets in the same population, the MNAR seems to better capture the problems in the older patient group.
When summarizing simple parameters for the screening for malnutrition in older adults, the following can be said :
An unintended weight loss of >5% of body weight within the last 3 months or >10% within the last 6 months
A clearly reduced body mass (fat and muscle mass): body mass index (BMI) <20 kg/m2 (please notice: the cutoff is higher in older adults than in younger ones, where the value is <18.5 kg/m2)
MNAR-SF <8 points (out of 14 possible ones)
It is therefore helpful to use a checklist when searching for insufficient nutritional or fluid intake (Table 21.3).
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