During the course of a meal, one needs to exert numerous coordinated actions. The aging process implies physiologically weakened muscles, the lack of natural teeth, and poor movement coordination, all of which cause difficulties in the eating process. Then older individuals who have depleted capabilities are more vulnerable to suffer malnutrition and have their life quality compromised. This chapter describes eating capability (EC) as a measurable term that represents the practical capability of an individual in food handling and oral consumption. By introducing this term, our main aims are to establish objective methods for the assessment of an individual’s capability of eating and to help caregivers make the right food choices for elderly individuals. EC consists of major components relating to food handling, oral food manipulation, sensing, and cognitive capability. Specific meanings and implications of each component are discussed in detail, with special attention given to the elderly. Some of the latest results in EC assessment are also explained in this chapter.
Eating capability; oral processing; hand manipulation; sensing capability; food for elderly
Physiologically, with the aging process, there is a decline in the functioning of all organs (Langley-Evans, 2009). There are changes in body composition (Rosenberg and Miller, 1992) such as a decrease in bone density and lean mass and an increase in body fat. Many of these changes translate into declining physical abilities and declining motor performances (Newell et al., 2006) that influence the normal execution of daily activities such as self-feeding. The self-feeding process involves numerous actions to be performed such as opening a food package, heating the meal, manipulating the food by hand or mouth, chewing, masticating, and finally swallowing the food bolus. Opening a package can be a difficult task for many individuals, especially for disabled elderly consumers (Heinö et al., 2008). Other physical impairments also tend to interfere with their abilities such as difficulty in transporting food from the plate to the mouth in the case of Parkinson’s disease sufferers, mastication inefficiency in edentulous or denture wearers (Fontijn-Tekamp et al., 2000), or swallowing disorders in dysphagia patients (Scialfa and Geoff, 2006). Elderly individuals who suffer from difficulties performing this entire eating process generally eat less food due to the fatigue and time consumed to perform these actions (McLaren and Dickerson, 2000), and this may result in malnutrition and deterioration of health. In fact, previous studies showed that common barriers among elderly to eat adequately have been related to difficulties in eating as well as the inability to prepare fruit- and vegetable-based meals (Dittus et al., 1995).
To our knowledge, eating difficulties in elderly populations have been studied mostly from the perspective of caregivers using nursing diagnosis through observation and interviews with patients having neurological pathologies (Axelsson, 1988; Jacobsson et al., 1996; Jacobsson, 2000; Norberg et al., 1987; Westergren et al., 2002). Generally in these qualitative studies, different eating actions (e.g., hand movements, oral manipulation, eating time, swallowing) with different levels of aberrancy are monitored. To complement the eating actions, an assessment of an individual’s nutritional status is also carried out, which shows a close association between low energy intake and malnutrition. To measure the eating disability in an acute stroke population, McLaren and Dickerson (2000) designed a study measuring eight different categories of eating action inabilities using direct observation. Within each category (arm movement, lip closure, chewing, reflex swallowing, posture, communication, attention and visual field loss, and perceptual loss), numerical values were assigned according to severity and level of impairment ranging from 0 (absence of impairment, disability or dependence) to 1, 2, and 3 (moderate to severe levels of impairment and dependence). As in previous studies, McLaren and Dickerson (2000) found a direct relationship between eating disability and reduced dietary energy intake.
Despite this valuable study, there is a lack of reliable instruments for eating assessments, and the outcomes from such assessments are often not comparable between different studies. Therefore, there is a need to establish easily quantifiable parameters and select methods for objective assessments of eating actions in order to consider elderly group heterogeneity and address appropriate foods for each individual. A new concept called eating capability (EC) was very recently proposed (Laguna and Chen, 2016) to represent an individual’s capability of oral food consumption. Based on the fact that an eating process involves a series of food − body interactions, EC is a combination of one’s physical, physiological, and mental coordination capabilities in handling and consuming food. This chapter focuses on the difficulties faced by the elderly during the eating process rather than the digestion of food after oral processing. The main objective of this chapter is to introduce different methodologies that can be used to quantitatively measure the eating process.
EC is defined as the physical, physiological, and cognitive capabilities of an individual in handling and consuming food. As shown in Fig. 10.1, the EC comprises different parameters: hand, oral, sensation, and mental and coordination capability. Each parameter of the EC can be characterized separately by measurable parameters. Mental and coordination capability are not discussed in this chapter due to its complexity and the lack of literature information on its implications to eating impairment. Hand, oral, and sensation capability will be discussed in the following sections. The most common devices used to measure these capabilities are shown in Fig. 10.2, which will be referred throughout this section.
Hands are the most versatile parts of the human body and essential tools for handling different situations in our daily lives. Any injury, disability, or distortion of the hand can affect our quality of life (Olandersson et al., 2005). With aging, hands suffer from numerous changes due to normal decline, common metabolic skeletal diseases such as osteoarthritis, rheumatoid arthritis and osteoporosis, hormonal changes, degenerative diseases of the central nervous system (CNS) such as Parkinson’s disease (Carmeli et al., 2003), or side effects of malnutrition. These changes result in diminished hand strength (Mathiowetz et al., 1985a) due to decreased muscle mass (Metter et al., 1998), stiffer tendons, and irregular or dense connective tissue (due to biochemical changes), swelling and joint deformation in case of osteoarthritis, fungal infections in nails, and peripheral decrement in tactile sensibility (Carmeli et al., 2003). During the eating process, the capability of hand manipulation is essential both before and during the course of a meal (food preparation and hand cutlery manipulation). This capability can be defined as the ability of an individual to exert an appropriate force in a coordinated manner so as to manipulate food from opening a package to reaching the food to bringing it to the mouth.
When it comes to food packaging, many consumers experience some difficulty in opening certain types of packaging (Heinö et al., 2008). The grip and coordination needed often varies. For instance, a wrist twist is needed to open big jars, a lateral pick is needed for certain small lids, and a finger grip is required for peelable packaging. Winder et al. (2002) noted that the difficulty in dealing with food package is one of the main barriers for elderly consumers in food consumption and is often a cause of packaging-related accidents, especially when inappropriate tools are used in the opening process (Lewis et al., 2007). Opening peelable induction seal on bottles and glass jars commonly present problems for elderly people, particularly for those who have hand disorders (Duizer et al., 2009). Dittrich and Spanner-Ulmer (2010) found that the main problems were the high forces required to open the packages, tearable openings being too small, and the opening mechanisms being too hard to see.
During the course of the Optimizing Food for the Elderly (OPTIFEL) Project (a European Union FP7 project), European older adults (65 and older) were put into three different categories based on their feeding dependency (Laguna et al., 2016a): (1) living at home and needing help for food purchasing, (2) living at home and needing help for meal preparation or having food delivered, and (3) living in a nursing home or sheltered accommodation and requiring full-time care. Participants were asked about package-related difficulties, and a significantly high percentage of elderly reported experiencing problems, especially when trying to open screw caps. Those elderly who suffered arthritis have great difficulties in opening jars and bottles (Wylie et al., 1999); those who suffer strokes typically have trouble manipulating food on the plate and transporting it to the mouth (Axelsson, 1988; Jacobsson et al., 1996, 2000; Westergren et al., 2001).
The action of grasping and lifting food objects from plate to the mouth is directed by a complex interplay between multiple sensorimotor systems to signal, analyze, and process the mechanical interactions and constraints between body and object (Nowak and Hermsdörfer, 2003). One class of forelimb movement is the reach to eat. In this movement, an individual takes the food up to the mouth (for eating) or to the nose (for smelling). When the hand reaches toward one’s face, tactile and proprioceptive (the perception of body position and movements in three-dimensional space) information concerning the location of facial features provides enough sensory information to accurately shape the digits for food grasping. The time to perform an action from visualizing the food to carrying out the required action is longer in the elderly than in younger populations (Coats and Wann, 2011; Seidler-Dobrin and Stelmach, 1998).
To overcome problems of hand manipulation, a range of adaptive eating utensils have been developed. Examples include a nosey cup to avoid bending the neck in the case of dysphagia, cutlery for people with grasping problems, plate guards to avoid spillage for people with low vision, and a weighted mug for those with tremor problems. Even though these tools are helpful, they only deal with a part of the eating difficulties. For example, patients with Parkinson’s disease have trembling hands and difficulty in coordinating cutlery on the plate and transporting food to the mouth (Andersson and Sidenvall, 2001), and individuals who suffer from skeletal muscle weakness (due to aging or pathology) have reported problems in handgrip precision and force (Kurillo et al., 2004).
The ability to manipulate food packaging and food by hand involves two dimensions: (1) adequate force to perform the movement (e.g., to lift a glass) and (2) a degree of coordination to execute the movement. These two dimensions are related and influence each other. For example, to open a so-called easy-to-open package, one has to have enough hand dexterity (or coordination) to initiate the peel force and then have enough force to tear the plastic apart. So, devices that cover these two dimensions—strength and coordination—will first be considered.
A hand dynamometer is an easy-to-use device for measuring hand strength (Sasaki et al., 2007). The Jamar Grip Strength Dynamometer (Lafayette Instruments, Indiana, USA) is the standard device used by clinicians (American Society of Hand Therapist) (see Fig. 10.2A). For several reasons (validation technique, accessibility to the product, ease of carry, ease of test performance, reproducibility, and price), this device has been used for the hand-strength measurement in assessing EC (Laguna et al., 2015a; Laguna et al., in press b). Previous authors have reported that handgrip strength can be related to lower limb strength (Lauretani et al., 2003) and general muscle strength (Budziareck et al., 2008; Norman et al., 2011). However, elderly patients suffering from different health disorders such as cerebral stroke (Hermsdörfer et al., 2003), peripheral nerve damage (Nowak and Hermsdörfer, 2003) or hand osteoarthritis (de Oliveira et al., 2011) cannot perform grip movements adequately. Other authors such as Kurillo et al. (2004) developed tracking systems to evaluate grip force control with different end objects for different hand positions (nippers, pinch, spherical, lateral, and cylindrical grips). This device is more versatile and capable of providing different types of gripping forces that are used in daily activities. Moreover, this proposed device records the track over time, allowing better understanding of sensory-motor control. Unfortunately, this device has never been replicated or validated.
The B&L pinch gauge (B&L Engineering, California, USA) is a standardized protocol (American Society of Hand Therapists) used in rehabilitation assessment. The Flexisensor (Laguna et al., 2015a) (see Fig. 10.2B) has been used to measure the finger-gripping force with a modified version of the device designed by previous authors (Flanagan et al., 2012). The modified setup consists of a built-in thin flexible force transducer (Tekscan, South Boston, Massachusetts, USA) connected to a multimeter. Two self-adhesive neoprene disks of 1 cm diameter are attached to the sensor to make the assessment comfortable for participants. The multimeter connected to the flexisensor registers resistance in ohms (the larger the force, the lower the resistance). To convert the registered resistance data into force values, a calibration is needed. Forces of magnitude from 5 N to 250 N were applied by a probe attached to the Texture analyzer (Stable Micro Systems, Godalming, UK), and resistance at each applied force was recorded. A standard curve of the applied force (N) and registered resistance can be used to convert the assessment into finger-gripping force. In the study conducted by Laguna et al. (2015a), elderly subjects were asked to squeeze the neoprene adhesive with their thumb and index finger, and the minimum resistance was recorded. Authors found that the finger-gripping assessment had the highest variability among subjects, as this precision assessment picks up even minor variability in subjects suffering from trauma (Palastanga et al., 2012).
Technical sensors. Hermsdorfer et al. (2003) developed a method for dynamically holding and transporting different spherical objects to analyze impairments of manipulative grip control in patients with chronic cerebral stroke. Values obtained from such assessments can give an effective indication of the strength and coordination of the hand (as well as finger) muscles and therefore the capability of food handling.
Timing and videorecording actions. Moving different objects at a measured distance depends on bimanual or unimanual movements (Coats and Wann, 2011, 2012). Thus, there is the possibility of using a standardized kit for manual dexterity (Mathiowetz et al., 1985b). This is a performance-based test of unilateral gross manual dexterity. Individuals move as many blocks as they can one at a time from one compartment of a box to another of equal size in 60 s. This kit provides a baseline for motor coordination. The test is quick and simple to administer and suitable for persons with limited motor coordination.
Older individuals have altered appetites and slower metabolic absorption of key nutrients, which can affect their nutritional status. This can be worsened by their inability to chew and swallow food (Walls and Steele, 2004) effectively and efficiently. For that, an adequate assessment of oral capability is needed. Oral capability is defined as the ability to transform nonswallowable food into a swallowable bolus and to transport it safely from the oral cavity into the stomach. It includes every oral action from the first bite up to swallowing (details are shown in Fig. 10.3). Very often, these oral actions are grouped into two sequential categories: (1) mastication capability and (2) swallowing capability. To perform these two actions, different structures work in a highly coordinated manner under the direction of the CNS: orofacial muscles, lips, cheeks, teeth, tongue, and palate (Koshino et al., 1997).
Mastication starts with the first bite of solid or semisolid food and is conducted by the forcible occlusion of the opposing edges of the upper and lower incisors (Okada et al., 2007). Then a succession of chewing cycles occurs (Woda et al., 2006) with the help of saliva or liquid released from the food to form a cohesive bolus (Jalabert-Malbos et al., 2007). The main components of the mastication process and swallowing are shown in Fig. 10.3.
Mastication takes place inside the oral cavity and has a close interaction with the sensory-motor system, including teeth, orofacial muscles, jaw muscles, labial muscles, the tongue, and the production of salivary secretions. All of these components work in a highly coordinated manner and under close control by the upper CNS, which generates efficient masticatory movements (Koshino et al., 1997). Because of the involvement of different parts, each must function properly. If one part is missing or is dysfunctional, the mastication capability will be diminished. In the elderly, different causes can impair mastication, including the loss of teeth, inadequate secretion of saliva, tongue problems, and loss of muscle mass with consequent decreases in biting force. Also, the pattern and rhythm of mastication is altered with age. For instance, the number of chew cycles increases progressively with age (Feldman et al., 1980; Peyron et al., 2004) to compensate for changes in food hardness, and the time needed for a chewing cycle decreases (Peyron et al., 2004).
The masticatory capability includes the execution of the first bite and the ability to use the teeth to grind or pulverize a chewable food into smaller particles (de Liz Pocztaruk et al., 2011; Hatch et al., 2001). During the first bite, the pressure exertion on teeth causes slight stretching to the periodontal ligaments and thus information is sent to the CNS for texture interpretation. The periodontal ligaments are able to detect extremely small forces (1 N or lower) (Lucas et al., 2004). Masticatory efficiency decreases for subjects who have missing teeth (Fontijn-Tekamp et al., 2000; Miyaura et al., 2000). The contacting area between upper and lower teeth is highly important for food oral breakdown, and fewer teeth means the biting force decreases (Laguna et al., 2015a). Replacing missing teeth with dentures can improve mastication but cannot always fully recover the efficiency of natural teeth (N’Gom and Woda, 2002). People who have lost postcanine teeth and replaced them with removable dentures (Fontijn-Tekamp et al., 2000; Kapur and Soman, 2006; Pocztaruk et al., 2008) have a much reduced masticatory function. Because of this reason, elderly people who usually suffer from tooth loss often have partially depleted mastication capability. Generally speaking, elderly patients with incomplete dentition (which is common in old age) swallow relatively larger food particles even though they may try to compensate for teeth loss by chewing longer (Woda et al., 2006). Bates et al. (1976) observed that loose dentures can even move during eating. In such cases, the tongue has to be used to stabilize and hold dentures within the mouth. This means that there is not only decreased efficiency for food oral breakdown but also the tongue must help position food while trying to retain the dentures. The dentition status can also influence an individual’s food choice. When dentition is low (i.e., a patient wears complete dentures), the intake of difficult-to-chew food items (e.g., roots, vegetables, fruits, and meat) becomes less pleasing. It is also possible that they avoid difficult-to-chew foods such as stringy foods like beef, crunchy foods like carrots, and dry foods like crusty bread (Hildebrandt et al., 1997). However, sometimes the desire to eat certain food products overshadows the lack of teeth (Laguna et al., 2015a).
When it comes to food preparation, those elderly patients with reduced masticatory efficiency often require extra work to prepare their food. For example, some fruits and vegetables must have their skin removed, and some foods must be overcooked to facilitate mastication (Walls and Steele, 2004). Table 10.1 summarizes the main problems denture wearers suffer in comparison with those who still have their natural teeth.
To measure biting force, different instruments have been used. Their positioning inside the mouth is critical for reliable measurements because different forces can be executed with different teeth and the area of contact is also different. With more teeth involved in the measurement, the assessment of the oral action could be more relevant to reality, even though dental studies commonly assess a single tooth or single tooth position to determine the efficiency of oral tooth implants (Flanagan et al., 2012). Up to now, various types of sensors for biting force quantification have been used. Tortopidis et al. (1998) used three different patterns of stainless steel force transducers to measure the biting force. These transducers used a similar model described earlier by Lyons and Baxendale (1990) in which two stainless steel beams with two strain gauges attached to each side of the beams are used with flexible epoxy resin and wire to form a Wheatstone bridge circuit. Probably the simplest one of these experimental setups is the one with only a single sensor connected to a multimeter (Fernandes et al., 2003; Flanagan et al., 2012; Laguna et al., 2015a; Laguna, 2016c,d; Singh et al., 2011) as shown in Fig. 10.2C. Because the flexisensor is available at an affordable price and reproducible, it has been used most frequently for EC assessments.
The number of teeth is another important factor. As already noted, fewer teeth results in a decreased bite force. To assess the dental status, researcher can observe and count the number of teeth or directly ask the elderly person if he or she has natural teeth, crowns, is edentulous, is wearing dentures, or a combination of these. Assessment of the impact of tooth loss is available in the Geriatric Oral Health Assessment Index (El Osta et al., 2014), a questionnaire regarding the functional dimension—pain and discomfort—and the psychosocial dimension. This has been used to evaluate problems related to food ingestion.
Characterization of masticatory capability can be carried out by using a standard (or representative) food material and measuring particle size reduction during mastication to indicate grinding capability. Peanuts, almonds, cocoa, carrots, jelly, hazelnuts, decaffeinated coffee beans, and nuts are the most frequently used food materials for assessing mastication (Gambareli et al., 2007; Schneider and Senger, 2002).
The preferred choices, however, are silicone-based artificial food materials (Pocztaruk et al., 2008). Various artificial test foods have been reported in literature—e.g., OptosilR, Optocal PlusR, and CutterSilR (Fontijn-Tekamp, 2004). The advantages of these materials are that they are inert to water and saliva (they are neither soluble nor enzyme responsive); are of homogeneous size, shape, and toughness; have no seasonal variation; and can be stored easily (Fontijn-Tekamp et al., 2004). Compared to food, artificial gels are much more stable and show little fluctuation in their physical and chemical properties. However, one big limitation is that these gels are not digestible and must not be swallowed (Pocztaruk et al., 2008). Other materials such as chewing gums, gelatin gels, paraffin wax, and a mixture of calcium carbonate have also been used as test foods (Ahmad, 2006).
To study the degree of food fragmentation different methods are often used, such as sieving, colorimetric determination, light scattering, and various image-analysis tools. All these methodologies will require mouth contents to be expectorated (or spitted) before swallowing. A potential problem is that saliva and particles can be swallowed accidentally during chewing. Yamashita et al. (2013) found that during the preparatory phase of swallowing, part of the oral bolus may pass to the pharynx before spontaneous swallowing is initiated. Because of this, caution must be taken when using these methods to assess real food boluses. In contrast to the food breakup method, van der Bilt (2010) developed a method to determine masticatory capability by assessing the mixing and kneading of food inside the mouth. Two chewing gums with different colors were placed in the mouth and chewed. The extent of color mixing was then measured as a function of chewing cycles, and the masticatory efficiency of the individual was assessed.
Recently, to incorporate the mastication assessment in EC assessments, participants were videorecorded (Laguna et al., 2016b). In those videos, participants were asked to eat normally texture-characterized products. By analyzing individual video frames, one can reveal the number of chews and oral-processing time. Other oral-processing aspects, such as expressions of difficulty, could also be taken into account. This technique was reliable for assessing number of chews and time needed to perform the eating process.
Saliva is a biological fluid naturally secreted from inside the human mouth. During eating, saliva helps in three processes: chewing, tasting perception, and swallowing. During chewing, saliva helps to form a coherent and smooth bolus by mixing and aggregating food particles (Sarkar et al., 2009). It also contributes to the sensory perception by functioning as a reservoir of food ingredients for a continuous flavor release (Doyennette et al., 2011). In the swallowing process, the mucins present in saliva create a slippery effect so that food bolus can easily slide through the esophagus (Pedersen et al., 2002), which is critically important for safe swallowing (Engelen et al., 2005).
With age, salivary glands can become disturbed and cause a decrease in saliva secretion (Samnieng, 2015). In addition, many pathological conditions linked with old age influence salivary secretion, especially medications that cause diminished salivary secretion. Head and neck irradiation and systemic conditions such as Sjögren’s syndrome and type 2 diabetes also can affect saliva production (Anurag Gupta et al., 2006). Elderly patients with xerostomia (i.e., mouth dryness) (Walls and Steele, 2004) not only will have problems of chewing food and swallowing but also problems of tasting and speaking as well as being intolerant of dentures (Narhi et al., 1992).
Saliva quantification is not generally measured in relation to nutrition status but is commonly studied in relation to drug metabolism by different collective methods that can be classified as nonstimulated and stimulated secretion. The latter involves chewing an inert material such as paraffin or being exposed to gustatory stimulation. In both cases, saliva is collected in a container for its biochemical characterization (Crouch, 2005; Topkas et al., 2012). For quantification purposes, Navazesh and Christensen (1982) used four different methods: draining, spitting, suction, and swabbing. Authors concluded that the flow rate did not differ significantly, although the swab technique was the least reproducible method.
The tongue is a mass of mobile muscle tissue inside the oral cavity. Its proper functioning is crucial for both eating and speaking. During oral food processing, the tongue acts as a mechanical device to manipulate and transport the food (Heath, 2002) and the dominant source of energy for initiating bolus flow (Alsanei and Chen, 2014). Chemoreceptors and mechanoreceptors on tongue surface act as the most delicate sensation systems capable of detecting and discriminating the taste and textural properties of food (Hiiemae and Palmer, 1999). The tongue (Hiiemae and Palmer, 1999) also helps to move food distally through the oral cavity, from the anterior to the pharynx (Pereira, 2012). Any dysfunction of the tongue (i.e., lack of coordination or motor disorder) will make eating and swallowing difficult (Ueda et al., 2004). One of the commonly known adverse effects of tongue dysfunction is pneumonia after food aspiration (Steele and Cichero, 2014). Tongue fatigue contributes to an incomplete food clearance, longer time to finish a meal, reduced food intake, and difficulty swallowing. For a young and healthy individual, this effect is not significant, but diminished tongue strength for the elderly often shows a significant decrease after meal consumption (Kays et al., 2010).
The available techniques to study tongue capability can be divided into those that measure the strength of the tongue against the palate and those that record images of tongue movement during oral processing and swallowing. In tongue − palate contact measurements, an indication of the contraction strength of tongue muscles is obtained. Devices for such assessments normally consist of two parts: a sensor inserted between tongue and palate and a register for data recording using the Iowa Oral Performance Instrument (IOPI), the Handy Probe System, or a multisensory system. Their sensors are the difference between them. IOPI uses a mobile plastic bulb (Ono et al., 2009) (see Fig. 10.2D) just like the Handy Probe System; both, however, are generally uncomfortable due to the presence of a sizable sensor inside the oral cavity. Incorrect bulb placement inside the mouth can cause errors (Butler et al., 2011). Multiple sensing probes are also used where three (or even more) air-filled bulbs are arranged in a sequence. When the tongue presses the hard palate, pressures at different locations can be determined and lead to a tongue-pressure profile rather than the pressure at a single point. However, the main disadvantage of such devices is their inevitable interference with normal tongue movement.
The palatal plate with multisensors consists of a plastic palate with sensors inserted where tongue pressure during both swallowing and mastication can be recorded. However, real applications of palatal plates can be difficult because the prostheses require advanced techniques and are expensive to manufacture. Furthermore, subjects often find them highly uncomfortable and usually need considerable amount of time to get used to the plates. Similar to a palatal plate is a sensor sheet consisting of five measuring points attached directly to the palatal mucosa with a sheet denture adhesive (Hori et al., 2009). The last two multisensors not only can measure the tongue pressing strength but also evaluate the tongue movement during mastication and the initiation of swallowing.
For the study of tongue movement during oral processing and swallowing, imaging techniques such as ultrasound, videofluorography and fiberoptic endoscopy are also available (Hori et al., 2009; Langmore, 2003; Palmer et al., 2000; Yamashita et al., 2013). Although they are useful for studying swallowing and provide a good understanding of the tongue behavior during the entire eating process, these techniques require clinical training, which makes them less accessible for research scientists and community applications. Moreover, they are qualitative techniques, and the time required to complete the test and image analysis is higher than the tongue − palate contact tests. For this reason, IOPI or a Handy Probe could be better choices for quick and reproducible tongue-strength assessments. The sheet sensor developed by Hori et al. (2009) allows accurate assessment of pressure at different points without dramatically interfering with mastication and swallowing. The great advantage of this technique in comparison with multiple sensing and palate sensors is that the superthin sensor sheet can be flexibly adapted to the hard palate without causing too much discomfort to the subject.
The IOPI device shows a decrement of tongue pressure with increases in age (see Fig. 10.4) (Alsanei and Chen, 2014). In the EC assessments carried out in 200 elderly subjects in the United Kingdom and Spain, a similar trend (age–tongue pressure) was found (Laguna et al., 2015a; Laguna et al., 2016b,c,d). The IOPI was chosen as a technique to measure tongue strength in elderly because it is easily available, reproducible, and allows comparison of new results with previously reported results in the literature using the same device in elderly groups.
Bolus swallowing is a transporting process that moves food from the oral cavity to the stomach via the oral–pharyngeal–esophageal tract. The whole process takes just a few seconds from initiation to completion (Dodds, 1989). A swift switch between breathing and swallowing is vital (Matsuo and Palmer, 2008) and achieved by physical closure of the airway by elevation of the soft palate (to seal off the nasal cavity) and titling the epiglottis (to seal off the larynx) along with neural suppression of respiration in the brainstem (Nishino and Hiraga, 1991).
A swallowing process is traditionally divided into four stages: (1) oral preparation, (2) the oral propulsive state, (3) the pharyngeal state, and (4) the esophageal state (Logemann, 2007). Disorders affecting the oral preparatory and oral propulsive forces usually result from impaired control of the tongue (Dodds, 1989) or dental problems (Palmer et al., 2000), while disorders in the pharyngeal and esophageal states is usually dictated by abnormality in the motor sequence or obstruction (caused, e.g., by tumors).
Dysphagia is the term often used to refer to swallowing disorders (Hori et al., 2009) in any of the previously described stages. Particularly in elderly population, dysphagia can lead to malnutrition and increase the risk of aspiration and pneumonia, leading to morbidity and mortality (Kaiser et al., 2010; Kikawada et al., 2005). The exact effect of aging on oropharyngeal swallowing is not yet fully understood and will require collaborative efforts from oral physiologists, food scientists, and clinical researchers (Logemann, 2007). The major risks of inappropriate bolus swallowing are aspiration and choking. The former is caused by accidental entering of food residues into the larynx pipe; serious coughing and even infection can follow if oral bacteria enter the larynx. The latter is caused when large food particles block the airway and could lead to fatal consequences such as suffocation. Nonoral feeding may be implemented when the patient cannot achieve adequate nutrition or hydration or if there is risk or aspiration (Leonard et al., 2014). Based on the preceding discussion, we could use the term swallowing capability to represent how an individual is capable of transporting the food bolus from the mouth to enter the stomach through the whole oral–pharyngeal–esophagus tract without causing aspiration or some other negative consequence to human health.
An objective assessment of swallowing process is not an easy task. The most common diagnosis is the swallowing evaluation in which subjects are asked to swallow a quantity of water and are then assessed for possible coughing or gurgling vocal sounds (Macht et al., 2014). However, this methodology has been criticized for its poor standardization and poor accuracy (McCullough et al., 2001). There are other sets of imaging techniques that can be used to clinically diagnose swallowing disorders such as videofluorography and fiberoptic endoscopy. In a videofluoroscope examination, a food with a certain fluid consistency is mixed with radioactive barium and fed to the patient who sits upright (Langmore, 2003; Palmer et al., 2000). Radiography images are recorded when a subject swallows barium-marked boluses of different consistencies; examiners are then able to determine how capable the patient is in dealing with a bolus (Palmer et al., 2000). Also, with videofluorography recording, the anatomical structure and motion of a food bolus can be monitored (Palmer et al., 2000). The main disadvantage of this technique is that patients are exposed to radiation and an endoscopic view of anatomical abnormalities is not possible.
In a fiber-optic endoscopic evaluation of swallowing, a flexible transnasal laryngoscope is inserted deep into the oropharyngeal region and then used to evaluate the path of bolus entry and coordination during a normal meal (Dua et al., 1997). The advantage of transnasal endoscopy is that it shows real-time swallowing with no oral invasion and therefore no influence on tongue movement. However, the nasal lidocaine that is applied to decrease discomfort during examination can affect the swallowing function (Macht et al., 2014). Despite the advantages of both techniques, their use is largely restricted to clinicians due to the required clinical expertise to use these techniques and therefore is not easily accessible to food scientists or community workers. Koshino et al. (1997) reported the use of ultrasound diagnostic equipment to study bolus movement, the onset and offset of bolus flow, and bolus moving speed. One great advantage of ultrasound assessment is that it is noninvasive. The attachment of ultrasound probes around the neck does not cause any noticeable impediment to bolus movement and actions of the tongue and other swallowing muscles. However, this technique gives qualitative information and frame-by-frame image analysis; unfortunately, the technique is highly time consuming and requires lots of images to be processed to provide statistical relevance.
For EC assessment, the IOPI has been used to measure tongue muscle strength, which is based on the fact that tongue pressing generates the first pushing force in creating bolus flow. However, it must be noted that tongue muscle strength assessment only gives information on oral propulsive capability. It does not provide information about possible abnormalities that occur in the pharyngeal and esophageal areas.
Sensing capability is the ability of an individual to evaluate and perceive sensory stimuli of a food through the five human senses (sight, smell, taste, touch, and hearing). The aging process is accompanied by a decreased efficiency in sensory perception and aggravated by pathological conditions such as stroke and pathological treatments such as chemotherapy for cancer treatment. The sensing perceptions losses and distortions decrease the perception of a food’s hedonic qualities, which decreases the overall enjoyment of eating and thus appetite and overall food intake. Some well-recognized effects of sense impairment on eating process are summarized in Table 10.2.
|Sense||Depleted Sensory Effect|
The consequences of sense impairment lead to decreased food sensory appreciation. Elderly persons with impaired taste sensation typically have decreased food consumption (Stanga, 2009), which contributes to the anorexia of aging. One easy solution is to add flavor enhancers to food (Schiffman and Warwick, 1993). This may help reduce one of the most common complaints by nursing home residents regarding food quality (Stanga, 2009).
To quantitatively assess an individual’s sensing capabilities, threshold detection has been found to be most practical. A person’s sensing capability can be assessed by three different thresholds (Meilgaard et al., 2006): the absolute or detection threshold, the recognition or identification threshold, and the difference threshold. The absolute or the detection threshold is the lowest intensity of a physical stimulus that is perceivable by human sense of smell, taste, or touch. The recognition or identification threshold is the level at which a stimulus not only can be detected but also recognized or identified. The difference threshold represents the smallest change in stimulation that a person can detect.
Despite their different natures, threshold values can be identified using similar approaches: an incrementing battery of intensities with a forced response of perception. For example, in hearing, the absolute threshold refers to the smallest level of a tone that can be detected by normal hearing when no other interfering sound is present; and in vision, the absolute threshold refers to the lowest level of light that a participant can detect. In relation to food, sensory thresholds to taste and odor are widely used. Various validated methods have been proposed by some organizations such as the American Society for Testing and Materials.
In the frame of the OPTIFEL project, several studies have been attempted using the EC concept in both young and elderly populations. With elderly populations, the main objective was to correlate food consistencies (or structure complexity) with individual’s EC score (Fig. 10.5). Our hypothesis was that the frailest elderly (with low EC) will find high-consistency or structurally complicated food difficult to eat, while those among EC group will be able to consume food of a wide range of consistencies or complexities. Elderly populations can therefore be grouped into clusters based on their objectively measured eating capabilities. Such clusters can be grouped based on the sum of the different capabilities: hand, oral, swallowing, sensing, and mental.
The EC model is in its early stages and the focus has been on hand, oral, and swallowing capacities. Only noninvasive, reproducible, reliable, and quick assessments have been used.
In the first stage (Laguna et al., 2015a,b), overall EC was measured using three key components—hand and oral capabilities and tactile sensitivity—among 203 elderly subjects living in the United Kingdom (n = 103 in seven community centers and two sheltered accommodations) and Spain (n = 100 in three nursing homes and one community center). Handgripping force was measured with an adjustable handheld dynamometer (JAMAR Dynamometer, Patterson Medical Ltd., Nottinghamshire, UK). Participants were asked to squeeze the hand dynamometer with one hand using maximum effort and maintain that grip for approximately three seconds; the grip on the other hand is then measured (Trampisch et al., 2012). The intensity of handgripping was displayed as the maximum force in the digital panel. Handgripping force was further studied to know if it can be used as a predictor of oral forces (Laguna et al., 2015a).
Finger-gripping force was measured with a modified version of the device designed by previous authors (Flanagan et al., 2012). The chosen technique for touching sensitivity was the Semmes-Weinstein monofilament test (North Coast Medical, Inc., Gilroy, California, USA) (Wiggermann et al., 2012) as shown in Fig. 10.2E. A Touch Sense monofilament was pressed in a perpendicular direction against the skin surface until the filament was bowed—approximately 1.5 s—and then removed. Tests began with the strongest monofilament, which applied a force of 300 g and continued in descending order down to the weakest filament with only 0.008 g force. Subjects were asked to give a signal when they sensed a touch. If no signal was given after filament pressing, this was taken as a failure to detect the touch by the subject. The value of the last monofilament that was detected by the participant was recorded as the touching threshold, which is taken as an indication of tactile sensitivity. Results of those participants who were unable to feel the monofilament of 300 g were eliminated.
For oral capability, denture status was asked and maximum biting force was measured. Participants were asked about their dentures and were classified into six different dental statuses: natural teeth, combination (natural with some crowns and bridges), full dentures, no teeth, just a few natural teeth, and bottom or top denture. For the maximum biting force, the designed device used in the previous study (Flanagan et al., 2012) was used for maximum biting force assessment. Two adhesive silicone disks (1.5 cm diameter, 0.3 cm thickness) were used to sandwich the force sensor. Participants were asked to bite the flexisensor with the incisors and hold the bite for a couple of seconds. The minimum resistance shown by the multimeter was recorded. As a hygienic measure, a new plastic film protector was used for each participant.
Tongue pressure was measured using the IOPI (Medical LLC, Redmond, Washington, USA) (Fig. 10.1E), which recorded tongue-palate pressure (Ono et al., 2009). Participants were asked to place the bulb in the center of the oral cavity between the tongue and the hard palate and press down with their tongues as hard as they could. The maximum pressure was recorded in kPa. Lip-sealing pressure was also measured using the IOPI. Participants were asked to place the bulb between their lips and then to press their lips as hard as they could. The maximum pressure was also recorded in kPa.
As shown in Fig. 10.6, a strong correlation was established between handgripping force and oral forces (tongue pressure, lip pressure, handgripping force, and biting force). The results suggested that the positive correlation between hand and orofacial muscle strengths in the elderly might lead to the possible use of noninvasive methods (hand force) to assess EC. However, this correlation might not be useful for participants who suffer from motor-illness pathologies.
All of the measured parameters (handgripping force, finger-gripping force, biting force, lip-sealing pressure, and tongue pressure) were normalized and converted to a score between 1 and 5, with 1 being the weakest. The collated and aggregated measure of EC was then used to characterize participants from weakest to strongest in four groups. To test the functional utility of this classification, participants were shown with a series of food pictures and were asked to rate how difficult it was to manage that particular food by hand (manipulating cutlery by performing tasks such as cutting or picking up food) and by mouth (oral processing through chewing, biting, and swallowing). As a conclusion, participants from the lower EC groups perceived fibrous and hard food products as significantly more difficult to consume than did participants with higher EC scores. However, the concept needed to be validated by examining real oral food processing with elderly patients—i.e., by measuring chewing cycles, bolus-swallowing time, and characterization of bolus as a function of EC score.
In a later study (Laguna et al., 2016a,b) food stimuli were given to elderly patients to observe their eating process. The food stimuli consisted of both food products of different textures and flavorless hydrocolloid gels (to avoid psychological and social bias) with different levels of structural heterogeneity. Finger-grip force and touch sensitivity were excluded from EC assessment due to the difficulty perceived by elderly subjects and the relatively low relevance of these assessments to EC assessment. A tool more relevant in terms of grasping and moving objects during the eating process was introduced, and manual dexterity was measured by a standardized kit.
The EC score was quantified this time, using the following equation:
where RH is the right handgripping force (kg), LH is the left handgripping force (kg), BF is the biting force (kg), TP is the tongue pressure (KPa), RD is the right-hand dexterity count, and LD is the left-hand dexterity count (using the manual dexterity kit). Subscripts Par and Str Par represent the individual and strongest individual scoring the highest in that particular test, respectively.
The maximum EC score was four points, with each test assessment contributing a maximum of one point. To calculate the value of each force for every individual, a fraction was generated. The denominator was the maximum value obtained for the test by the strongest participant, and the numerator was populated with values for the participant under study. Participants with EC of less than 2 were placed in cluster one (the weakest group); participants with EC between 2 and 3 were placed in cluster two, and participants with eating capabilities of more than 3 were placed in cluster three.
The key conclusion was that bite force differed by EC group, and was significantly different by dental status and influenced both liking, number of chews, and difficulty perceived. Other EC parameters had little influence on the oral processing of real food and gels.
With ageing, elderly’s food and energy intake tend to decrease due to diminished capability for eating, which results in compromised nutritional status for most elderly individuals and an increased incidence of morbidities. These vulnerable consumers may have different problems in food handling, oral manipulation, sensing, and perception as well as swallowing. The causes of these problems are physiological or pathological. One top priority for the food industry and caregiving industry is to provide foods that are safe to consume by these consumers. Objectively measuring an individual’s EC may help to correctly assess his or her abilities of food handling, food oral manipulation, sensation, and cognition. This chapter covers different objective assessments of physical and oral capabilities and how such capabilities can be integrated into a unique EC score. Such scoring might help food designers develop foods with textures that are just right for elderly consumers.