16 Swallowing Disorders in the Elderly

Ozlem E. Tulunay-Ugur

Introduction

According to the U.S. Department of Health and Human Services, persons over the age of 65 currently represent 12.9% of the American population. As the fastest-growing segment of the population, this age group is expected to expand to 30% by the year 2030. Dysphagia is a growing health concern in the aging population. Its prevalence is high in both the unhealthy and the community-dwelling elderly population and is associated with increased risks of malnutrition and aspiration pneumonia.¹ Although the exact incidence of dysphagia across different settings is unclear, conservative estimates suggest that 15% of the geriatric population is affected by dysphagia.¹ The prevalence is much higher in selected populations, such as patients residing in nursing homes, who have reported rates as high as 30 to 40%.² Aside from leading to malnutrition, dehydration, and aspiration pneumonia, dysphagia also has major effects on social and psychological well-being.³ Due to the complex nature of the swallowing system and because the workup and treatment encompasses multiple disciplines, several aspects of the problem remain poorly understood.

Changes in the Physiology of Swallowing with Aging

Age-related changes place older adults at risk for dysphagia for two major reasons: first, natural, healthy aging alters head and neck anatomy as well as the physiological and neural mechanisms that sustain swallowing function. This progressive change contributes to the alterations in swallowing in healthy older adults, and is termed presbyphagia, which is also associated with a diminished functional reserve. Second, disease prevalence increases with age, and dysphagia is a comorbidity of many age-related diseases and/or their treatments.⁴

Swallowing incorporates a complex system of both voluntary and involuntary sensory and motor behaviors. Six cranial nerves and ~ 40 sets of bilaterally innervated muscles coordinate the upper aerodigestive system, which coordinates the main functions of breathing and swallowing. Swallowing occurs in four phases: the oral preparatory, oral phase, pharyngeal phase, and esophageal phase. A large number of muscles and structural movements of bone and cartilage are involved in the following tasks: (1) preparing food in the mouth for swallowing, (2) propelling food through the oral cavity, and (3) propelling food through the pharynx and into the esophagus.⁵ To execute swallowing safely, the upper aerodigestive tract reconfigures from a system that valves and moves air for the purposes of breathing and talking to one that interrupts airflow and protects the airway while food, fluid, secretions, and medications are allowed to move into the digestive system for nutrition and hydration.⁴ With aging, a reduction in muscle mass and connective tissue elasticity results in loss of strength and range of motion.¹ Aging causes several significant changes in the oropharyngeal swallow, although usually the swallowing mechanism maintains a functional ability to propel food safely and efficiently from the mouth through the pharynx and into the esophagus. The overall effect of aging is to slow deglutition and to mildly but significantly reduce swallowing efficiency.⁶

The oral tongue is the primary propulsive force controlling and forcing the bolus into the pharynx. Todd et al corroborated the findings of Robbins et al and others who reported that isometric tongue strength decreases with age. Furthermore, they demonstrated that, since young and older adults generate similar swallowing tongue strength, swallowing is a submaximal strength activity; yet older adults have less functional reserve.^7–9 The decrease in isometric tongue strength in older adults has been postulated to be due to generalized weakening of skeletal muscle caused by sarcopenia.¹⁰ Nicosia et al showed that patients with oral phase dysphagia had lower isometric tongue strength compared with a control group; and Lazarus et al confirmed similar findings in patients with head and neck cancer.10,11 The role of tongue strengthening exercises in the treatment of dysphagia is not yet clear and requires further evaluation.

Another significant change in pharyngeal swallow with aging is a slightly delayed triggering of the pharyngeal stage.⁵ In those over age 65, the initiation of laryngeal and pharyngeal events, including laryngeal vestibule closure, is significantly longer than in younger adults.⁶ Although this may put the elderly at risk for penetration and aspiration, in this population the importance of either one of these consequences is still not thoroughly understood. Using flexible endoscopy and the penetration aspiration scale (PAS), Butler and colleagues reported the prevalence of penetration and aspiration to be 15 and 6.5%, respectively, in normal elderly individuals.¹² Alternatively, Allen et al suggested that penetration and aspiration during swallowing represent pathological entities that are not present in people with normal swallowing function. They looked at the prevalence of penetration and aspiration on videofluoroscopic swallowing studies (VFSSs) in normal individuals without dysphagia. One individual aspirated on VFSS, and penetration, which was present in 11.4% of normal adults, was even more common with a liquid bolus.¹³ Although the implications of penetration and aspiration continue to be studied, one of the well-known associated risk factors is pooling in the pyriform sinuses and the resultant overflow into the laryngeal vestibule. Upper esophageal sphincter (UES) dysfunction can be a major contributor to postswallow residues. Logemann et al evaluated the biomechanics of the swallowing of eight healthy adults between 21 and 29 years old and eight healthy adults over 80 years old. The study revealed that the movement of the hyoid and larynx to open the UES was identical to the point of the upper sphincter opening for both groups. However, there was a significant difference between the hyoid and laryngeal movements after UES opening. Following the UES opening, the younger men continued the anterior motion of the hyoid bone until they achieved upper sphincter opening and went further by 8 mm. In older subjects, the hyoid anterior movement was just enough to get the UES open and only 1 to 2 mm more. The difference between the amount of hyoid anterior movement needed to open the upper sphincter and the anterior amount of movement actually used in total reflects the functional reserve present in any given individual. Logemann and colleagues concluded that, although older men seemed to be more efficient in hyoid anterior movement and achieving UES opening, they in fact exhibited no reserve. Functional reserve is needed to assist in recovery when someone becomes ill and loses muscle strength.¹⁴

Contributing Factors

Skeletal muscle strength begins to decline at approximately age 45 and is associated with a 30 to 40% decrease in strength by the age of 80.¹⁵ This loss of muscle mass not only causes a reduction in strength, but also may be responsible for as much as a 30% decline in the highest rate of oxygen utilization an individual can achieve while performing an exercise requiring substantial skeletal muscle mass.¹⁶ Loss of skeletal muscle mass below a critical threshold, known as sarcopenia, leads to functional impairment and frailty. Sarcopenia of the lingual muscles correlates with malnutrition, and tongue thickness also correlates with midarm muscle area thickness. It has been suggested that exercises improving tongue thickness and strength could improve oropharyngeal dysphagia.¹⁷

Xerostomia can hinder bolus flow and results in the retention of material along the upper digestive tract. Functional salivary production has been shown to remain fairly stable throughout the age spectrum, although older adults have some decrease in salivary reserve due to the loss of saliva-producing acinar cells. Consequently, the drying effects of medications are generally more pronounced in older adults.⁴ More than 400 drugs are known to cause xerostomia, and the older adult is generally on multiple classes of drugs known to be offenders, such as anticholinergics, antihypertensives, antipsychotics, anti-Parkinson agents, diuretics, and sedatives. Xerostomia can also result from diseases such as Sjögren syndrome and scleroderma.

Neurological and neuromuscular disorders are among the most important causes of dysphagia in older adults. Stroke, Alzheimer disease, dementia, and Parkinson disease are all commonly associated with dysphagia. Dysphagia is highly prevalent following stroke, with estimates ranging from 30 to 65%.^18,19 Complications associated with poststroke dysphagia include pneumonia, malnutrition, dehydration, increased length of hospital stay, increased rehabilitation time, increased mortality, and increased health care costs.^1,4,20 About 25% of stroke patients die of aspiration pneumonia within the first year of rehabilitation.

It has been estimated that up to 45% of patients institutionalized with dementia have some degree of swallowing difficulty.²¹ Patients with dementia show slowing of the swallowing process, which may lead to increased time needed to finish meals and, as a result, malnutrition. In addition, cognitive impairment, motor deficits, and loss of appetite lead to further difficulties with feeding. Pneumonia is one of the many dysphagia-related health problems seen in this group, and indeed is one of the common causes of mortality.^1,22

Clinical Assessment: History

Dysphagia is likely to be underestimated in the older adult. Often perceived as a normal part of aging, it may not be brought up by the patient as a complaint until significant changes in diet have been made to compensate. Therefore, diligence is necessary and mandates a thorough history on all geriatric patients. Most patients will present with the complaint of “food getting stuck” in their throat. The site at which a patient localizes dysphagia is of limited value. Although dysphagia in the retrosternal or epigastric areas frequently corresponds to the site of obstruction, dysphagia localized to the neck may be from either the lower esophagus or the hypopharynx.23 Nonetheless, a careful history can help differentiate between oropharyngeal and esophageal dysphagia. Patients with oropharyngeal dysphagia will more commonly exhibit symptoms of coughing/choking during meals, especially with liquids. They may also have nasal regurgitation and problems with oral competence.

A clear understanding of the current diet of the patient is important. The types of foods causing difficulty should be determined, as well as the number of meals eaten during a day, aiming to understand whether the patient has an adequate nutritional intake. Unintentional weight loss in the elderly is generally a sign of malnutrition and increases the risk of opportunistic infections such as pneumonia. By leading to malnutrition, dysphagia promotes frailty, which in turn may worsen the dysphagia in older adults.

Aspiration risk should be carefully assessed and may be present at either initial swallow or postswallow due to residue in the hypopharynx. As a result of altered superior laryngeal nerve function in this population, silent aspiration is not rare. A history of aspiration pneumonia and hospitalizations should be sought and noted. In the United States, the prevalence of aspiration pneumonia in nursing homes has been reported to be as high as 8%.²⁴

Regurgitation of undigested food, solid food dysphagia, borborygmi in the throat, postprandial or nocturnal coughing, and halitosis are all symptoms that should raise suspicion of the presence of a Zenker diverticulum. These patients are also at risk for malnutrition, dehydration, and aspiration pneumonia. A history of neurological disorders, prior surgeries, or head and neck cancer treatment should alert the clinician to the possibility of dysphagia. The cognitive status of the patient is of importance to understand the inherent difficulties with feeding as well as to plan therapeutic strategies.

Physical Examination

A thorough head and neck examination with special attention to cranial nerve function should be performed. In examining the oral cavity, the presence of xerostomia should be noted. Indirect or direct (flexible) laryngoscopy, an integral part of the examination, may reveal pooling in the vallecula or pyriform sinuses, vocal fold hypo-/immobility, or a glottic gap during phonation (incomplete glottic closure).

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