However, not all patients with physiologic abnormalities of the swallowing mechanism show obvious delay in bolus flow or misdirection of bolus flow. The question that may arise for the clinician (and often for the researcher who has selected a cohort of patients with dysphagia) is the degree of severity of physiologic changes in the swallowing musculature needed before a patient is classified as having dysphagia. For instance, physiologic changes in the swallowing musculature have been described in older persons ²—such as reduction in tongue strength or esophageal motility—both of which may delay the delivery of food or liquid to the stomach. However, only when such changes result in perceptible changes in eating habits or associated medical complications such as undernutrition or aspiration pneumonia is a person classified as truly having dysphagia. Because swallowing is a dynamic process, persons may not exhibit signs and symptoms of dysphagia with every swallow and every bolus type. In these cases, they may be considered to be at risk for dysphagia or, alternatively, operationally defined as dysphagic. It is also possible that the swallowing musculature is normal but the patient is not alert enough to use that musculature because of his or her decompensated medical condition. In such cases it is assumed that attempts to swallow would result in dysphagic complications. In these cases, the patient may be classified as at risk for dysphagia. Patients may demonstrate abnormalities of behavior that interfere with the normal swallowing process; these may cause dysphagic signs and symptoms or put the patient at risk for dysphagia. Therefore dysphagia is defined not only by abnormalities of the mechanics of the swallowing musculature, but also by the consequences of failure, or potential failure, of that musculature owing to factors not always specifically related to swallow mechanics. For this reason the authors prefer the definition of dysphagia offered by Tanner³: “Dysphagia: [an] impairment of emotional, cognitive, sensory, and/or motor acts involved with transferring a substance from the mouth to stomach, resulting in failure to maintain hydration and nutrition, and posing a risk of choking and aspiration” (p. 152).

CLINICAL CORNER 1-2

M. M. was admitted to the burn unit with severe burns to the head, neck, and upper torso. Because of associated pain he was heavily sedated. As his condition improved and before he was allowed to eat orally, a request for a swallowing evaluation was made because it was noticed he was not swallowing his secretions well. The evaluation of swallowing revealed normal strength of the swallowing musculature; however, he was disoriented and could not maintain his alertness level for more than 30 seconds. Because of his poor mental status and alertness level he was not allowed to eat and was considered to be at risk for dysphagia.

CRITICAL THINKING:

1. How might medications contribute to dysphagia?

2. Could poor mental status result in choking? Give some examples.

CLINICAL CORNER 1-3

L. T. was admitted to the psychiatry unit with symptoms of acute schizophrenia. When eating, it was noted he would take excessive time to finish, with intermittent choking episodes. The speech pathologist who evaluated him for signs and symptoms of dysphagia found that the oropharyngeal swallowing musculature was intact. As she watched the patient eat, she noted a rapid feeding rate with inappropriate bite sizes. She also noted excessive talking while eating, and the choking episodes occurred during these talking periods. The patient was classified as dysphagic as a result of emotional and behavioral abnormalities.

CRITICAL THINKING:

1. What other types of behavioral disorders might contribute to dysphagia?

2. Why did this patient choke while eating and talking?

A swallowing disorder should be distinguished from a feeding disorder. A feeding disorder is impairment in the process of food transport outside the alimentary system. A feeding disorder usually is the result of weakness or incoordination in the hand or arm used to move the food from the plate to the mouth. In the United Kingdom and the United States a feeding disorder, particularly in the context of infants and children, may be the same as a swallowing disorder. Persons with feeding disorders (motor transfer problems) also may be dysphagic, such as those with cerebral palsy whose neurologic disability affects both feeding (motoric transfer) and swallowing. It is not known whether a feeding disorder that might require assistance with food transport also affects the subsequent act of swallowing, perhaps by interfering with timing of swallowing events.

A swallowing disorder also is to be distinguished from an eating disorder such as anorexia or bulimia nervosa. Whereas patients with dysphagia, bulimia, and anorexia may have difficulty with poor appetite, changes in dietary selections, and problems with the oral preparation of the bolus, patients with bulimia and anorexia rarely have demonstrable changes in or complaints of swallowing difficulty.⁴

INCIDENCE AND PREVALENCE

The incidence of a disorder is the reported frequency of new occurrences of that disorder over a long time (usually at least 1 year) in relation to the population in which it occurs. The prevalence of a disorder is the number of cases in a population during a shorter, prescribed period, usually in a specific setting. Exact measures of the incidence and prevalence of swallowing disorders in large and various populations are impossible because of differences in accepted definitions of dysphagia, the setting in which it is measured (acute, rehabilitation, chronic), and differences in the measurement tools across studies to detect it.⁵ For instance, asking a patient if she or he has a swallowing disorder to determine the prevalence is a very different method of detection compared with the use of an instrumental examination such as videofluoroscopy. Most demographic data that are reported relating to swallowing disorders are prevalence data. The importance of knowing the prevalence of a disorder can help guide clinicians in the detection of that disorder and therefore helps plan how resources might be devoted to that disorder. For instance, if an examiner knew that a certain abnormality was found in less than 1% of that population, the examiner may not spend time looking for that abnormality because its expected frequency of occurrence would be low. If, however, a particular abnormality was found in more than 50% of the persons with a particular disorder, the examiner would be alerted to expect the occurrence of deficits associated with that disorder. Therefore if the data suggested that 50% of patients who have had an acute stroke could have dysphagia, and that 20% of that group might have silent aspiration, an examiner would expect that half of the patients with acute stroke would have swallowing impairment and about half of those are at high risk for silent aspiration. Furthermore, pneumonia develops in 37% of acute stroke patients with aspiration.⁶ Knowledge of these prevalence data provides valuable assistance to medical personnel who initially screen for and manage the medical complications after acute stroke (see Chapter 4).

CLINICAL CASE EXAMPLE 1-1

The hospital’s chief of staff was reviewing a request from the dysphagia team to hire an additional speech pathologist and dietitian to screen and treat patients on the hospital’s new stroke and acute geriatric units. Part of the rationale for the request was based on recent published guidelines from the Centers for Medicare & Medicaid Services that screening for dysphagia on a stroke unit was prudent because of evidence that early detection may prevent associated morbidity and mortality, both of which would increase costs for the health care system and, by implication, the hospital. Furthermore, prevalence data from five studies were submitted indicating that at least half of the patients on the stroke unit and a similar number on the acute geriatric unit may have dysphagia. The financial officer estimated that early detection and treatment of dysphagia would result in a cost savings that far exceeded the cost of the two new employees who would be assigned to those units. After integrating the request from the dysphagia team, the evidence from the literature on prevalence, and the potential cost savings to the medical center, the chief of staff approved the request.

The American Speech-Language-Hearing Association (ASHA) estimates that 6 to 10 million Americans show some degree of dysphagia, although it is not known how these estimates were made.⁷ Kuhlemeier⁸ reported that the incidence of reported dysphagia in the state of Maryland rose from 3 in 1000 in 1979 to 10 in 1000, probably as a result of better reporting methods. Using these estimates, approximately 25,000 persons in Maryland in 1989 had dysphagia as either a primary or secondary diagnosis.

Prevalence by Setting

Estimates of prevalence of dysphagia vary by setting because certain age groups (older adults and newborns) and diagnoses (neurogenic) are more likely to demonstrate dysphagia. For instance, patients entering a rehabilitation setting may not have as many accompanying medical problems and dysphagia as those entering a nursing home. Conversely, infants born prematurely may have many medical problems that may secondarily result in dysphagia. In a survey of the entire population of an acute general hospital, fewer patients with dysphagia would be found in the general population compared with a survey of a special section of that hospital, such as the stroke unit.

Community

Estimates of the prevalence of dysphagia among older persons living in the community range from 16% to 22%.9,10 One study reported on the prevalence of dysphagia in a younger cohort (14- to 30-year-olds) living in the community who had been referred for complaints of dysphagia.¹¹ In this selected group, 70% had demonstrable pathologic conditions that accompanied their symptoms.

Acute and Chronic Geriatric Care

Of the 211 patients admitted to an acute geriatric unit in Singapore, the prevalence of dysphagia was 29% on admission and 28% at discharge.¹² In a nursing home in Maryland (chronic care), as many as 60% of residents had a combination of swallowing and/or feeding difficulty.¹³ One study found that when feeding and swallowing difficulty were combined, as many as 87% of the residents in a home for the aged were at risk for inadequate oral intake.¹⁴ Follow-up data of nursing home residents with oropharyngeal dysphagia indicate a mortality rate of 45% at 1 year.¹⁵

Acute General Hospitals

Using the Fleming Index of Dysphagia, a tool to identify dysphagia, Layne et al.¹⁶ found that nearly one third of their patients had a diagnosis consistent with dysphagia. These findings were nearly 18% higher than those provided by Groher and Bukatman,¹⁷ who reported a 13% prevalence rate in similar settings. The discrepancy in prevalence was explained by the fact that patients who were dehydrated in the study by Layne et al. were classified as dysphagic, whereas this was not a marker for dysphagia used in the collection of the Groher and Bukatman data.

Acute Rehabilitation Unit

Of 307 consecutive admissions to an acute rehabilitation facility, one third of patients were dysphagic.¹⁸ Of this group, half had dysphagia as a result of a stroke, followed by traumatic brain injury (20%), spinal cord injury and brain tumor (7%), and progressive neurologic disease (5%). On admission, the patients with the most severe dysphagia were those with traumatic brain injury, followed by stroke. The least severe dysphagia occurred in those with brain tumors.

Special Populations

Some primary medical diagnoses are more likely to precipitate dysphagic symptomatology, such as diseases that affect the central and peripheral nervous system and disorders affecting the structures of the alimentary tract, such as cancer. An estimated 300,000 to 600,000 persons in the United States each year are affected by dysphagia from neurologic disorders alone; most cases occur after a stroke.⁵ If these data are reliable, dysphagia is a common symptom after a stroke.

Stroke

Prevalence reports of dysphagia after stroke depend on when in the course of recovery the detection of a swallowing impairment was made. For instance, in acute stroke (less than 5 days after onset) the prevalence of dysphagia may be as high as 50%, whereas 2 weeks after stroke only 10% to 28% of patients may be dysphagic. Recognizing these discrepancies, Smithard et al.¹⁹ provided follow-up of 121 (untreated) acute stroke patients for 6 months using a clinical dysphagia examination and videofluoroscopy to detect swallowing deficits. Immediately after stroke, 51% were believed to be at risk for aspiration. After 7 days, only 27% were still considered to be at risk. At 6 months, 3% of the survivors had persistent difficulty, whereas 3% who previously were not dysphagic were now considered at risk. These results suggest that early detection is important in preventing dysphagic complications and that a significant number of patients will improve without intervention specific to their dysphagia. Similarly, comparable prevalence figures for dysphagia on admission (43% to 51%) were found by Gordon et al.²⁰ and Mann et al.,²¹ although the latter group noted a higher prevalence of dysphagic symptoms at 6 months (50%) than other studies with prevalence rates that ranged from 3% to 9%.^19,21 Daniels et al.²² found that 36 (65%) of 55 patients with acute stroke had dysphagia. Of these 36, more than half aspirated. Of these, two thirds did so silently, suggesting that events of aspiration could be detected only by videofluoroscopy, not the bedside examination. In long-term follow-up, 94% of these patients returned to oral intake. Interestingly, the presence or absence of silent aspiration did not discriminate between patients who returned to successful oral feeding.

Head/Neck Cancer

Surprisingly, there have been no large studies of the prevalence or incidence of swallowing disorders in unselected patients after treatment for head/neck cancer, although it is well known that dysphagia is a frequent complication. Dysphagia can be result from the removal of tissue, with subsequent sensory and motor loss, and the effects of radiation therapy and chemotherapy. Before patients in their study received treatment, Pauloski et al.²³ found that 59% had symptoms consistent with dysphagia. In a large multicenter treatment trial of patients with laryngectomies who were treated with either surgery and radiation or radiation and chemotherapy, approximately 33% had some type of swallowing-related difficulty at 2-year follow-up.²⁴ In a series of 46 patients treated by supraglottic laryngectomy, 60% had dysphagia after their hospital stay.²⁵ Evidence suggests that patients with pharyngeal tumor resections and those with tumors involving the tongue base are more likely to have dysphagia.²⁶

Head Injury

Dysphagia is common after severe head injury. Data report that the incidence of dysphagia ranges from 4.5% (9 of 199) of consecutive admissions in an acute care setting ²⁷ to an incidence of 78% (31 of 40) in a similar setting.²⁸ Discrepancies in reporting may be attributable to the initial severity of the injury and the method used to detect and define dysphagia. Incidence data are available for patients who survive head injury and enter a rehabilitation setting; the incidence ranges from 27% to 30%^27,29 to 42% (218 of 524).³⁰ In a mixed group (type of injury and time after onset), Lazarus and Logemann³¹ found that approximately half of the patients they examined with videofluoroscopy showed evidence of dysphagia. Among patients with head injuries entering a rehabilitation setting, Winstein²⁹ found that 27% were dysphagic on admission to rehabilitation and that only 6% were dysphagic after 5 months of rehabilitation. Of 62 consecutive patients receiving outpatient rehabilitation, Yorkston et al.²⁸ reported that 13% remained dysphagic. In general, the more severe the initial injury, the higher the incidence of dysphagia. Some patients remain comatose and are unable to eat, whereas others require extensive neurosurgical procedures with prolonged intubation and mental status changes, all of which may preclude attempts at oral ingestion. However, once patients enter the rehabilitation setting, their chances of returning to oral feeding are good.