Epidemiology of dysphagia in stroke patients

The location and severity of a stroke lesion will determine its effects on swallowing function. Hemispheric and brainstem strokes are both associated with dysphagia; however, unilateral hemispheric strokes are less likely to cause problems because there is bilateral representation in the brainstem (Morrell, 1992). Also, posterior lesions that do not affect the motor cortex may not lead to dysphagia (Logemann, 1983c).

Brainstem and anterior cortical strokes most often lead to dysphagia characterized by a delay in triggering of the swallow reflex. Dysfunction of the cricopharyngeal muscle is also common (Logemann, 1983a; Morrell, 1992). In cortical strokes, lingual and pharyngeal paresis may be unilateral, thereby allowing for compensation by turning the head toward the paretic side while swallowing (Mendez, Friedman, and Castell, 1991).

Because dysphagia is so often a temporary result of an acute stroke, we have limited our discussion to those studies that specifically examined the occurrence of dysphagia shortly after an acute stroke event using the water swallow test, Bedside examination (BSE), videofluoroscopic swallowing study/modified barium swallow (VFSS/MBS), or fiberoptic endoscopic examination of swallowing/fiberoptic endoscopic examination of swallowing and sensory test (FEES/FEESST). Any studies that did not define their diagnostic method, tested patients for dysphagia later than 7 days post-stroke, included transient ischemic attacks (TIAs), or that did not test 100 percent of the consecutive stroke population for dysphagia were excluded. This eliminated 8 out of 19 studies identified (Berg and Mor, 1995; Chua and Kong, 1996; Gresham, 1990; Hamdy, Aziz, Rothwell et al., 1997; Robbins, Levine, Maser et al., 1993; Selley, Roche, Pearce et al., 1995; Taub, Wolfe, Richardson et al., 1994; Teasell, Bach, and McRae, 1994). Evidence Table 3 shows the study results from 13 worldwide studies of the diagnosed occurrence of dysphagia after a CVA.

Many of these studies were hospital surveys; this may be an advantage; such studies interview patients just after the acute CVA because dysphagia is often most severe immediately after the event (Barer, 1989; Smithard, O'Neill, England et al., 1997; Smithard, O'Neill, Parks et al., 1996). This allows us to assess specifically the occurrence of dysphagia across studies without the confound of time variations.

Of studies conducted exclusively in a hospital setting, the reported occurrence of dysphagia among stroke patients ranged from 19.4 percent (Nilsson, Ekberg, Olsson et al., 1998) to 90 percent (Kidd, Lawson, Nesbitt et al., 1993). Diagnosis in the Kidd study was made on the basis of videofluoroscopic study; this method often increases the number of positive tests because it detects silent aspiration as well as symptoms that are not detected by and may never affect the patient. This is supported by the fact that these same authors assessed the same 60 patients using a water swallow test, and only 25 patients (41.7 percent) were diagnosed dysphagic on the basis of coughing, choking, or wet voice. There is an overall trend in the hospital-based literature that diagnosis made using results of VFSS result in higher prevalence rates [65.5 percent (Daniels, Brailey, Priestly et al., 1998); 74.6 percent (Daniels, McAdam, Brailey et al., 1997); and 90 percent (Kidd, Lawson, Nesbitt et al., 1993)] than those studies using other methodologies such as observation and BSE [19.4 percent (Nilsson, Ekberg, Olsson et al., 1998); 29.4 percent (Barer, 1989); 30 percent (Axelsson, Asplund, Norberg et al., 1989); 31.5 percent (Smithard, O'Neill, England et al., 1997); 41.7 percent (Kidd, Lawson, Nesbitt et al., 1993); 45.1 percent (Gordon, Hewer, and Wade, 1987); 49.6 percent (Smithard, O'Neill, Parks et al., 1996); 59.0 percent (DePippo, Holas, and Reding, 1994)].

One study did not limit its patient pool to hospitalized patients (Wade and Hewer, 1987). Wade and Hewer (1987) reviewed all records of stroke patients for whom evaluation of swallowing function (as measured by a water swallow test) was available within the first 7 days after the stroke event. They did not report overall swallowing disorders or dysphagia, but rather reported occurrence of individual symptoms: 14.2 percent choked, 6.2 percent displayed an abnormal swallowing pattern, and 22.6 percent demonstrated an abnormally slow swallow. It is impossible to determine the overall rate of swallowing disorders from this study because many patients may have shown more than one symptom; however, this study does provide a portrait of the typical symptoms experienced by a stroke patient.

The occurrence of dysphagia in a stroke population may differ depending on where the stroke occurred (left hemisphere, right hemisphere, both, or brainstem). It used to be thought that dysphagia occurred primarily after brainstem strokes, but more recent evidence suggests that it occurs at a similar rate after hemispheric strokes (Lugger, 1994). Of the studies discussed above, most of those that reported lesion location had a patient population made up largely of hemispheric stroke patients (85 to 100 percent of patient pool) (Barer, 1989; Daniels, Brailey, Priestly et al., 1998; Gordon, Hewer, and Wade, 1987; Kidd, Lawson, Nesbitt et al., 1993; Nilsson, Ekberg, Olsson et al., 1998). The reported occurrence of dysphagia in these patient populations ranged from 19.6 percent (Nilsson, Ekberg, Olsson et al., 1998) to 65.5 percent (Daniels, Brailey, Priestly et al., 1998). No studies exclusively examined a brain-stem stroke population.

There is consistent evidence that dysphagia is a transient symptom for many stroke patients. Barer (1989) followed 357 hemispheric stroke patients admitted to a hospital within 48 hours of the event. Swallowing was assessed with a water swallow test. At day 1 assessment, 105 of 357 patients demonstrated swallowing impairment (29 percent). This decreased steadily until, at 6 months, only 1 out of 248 (0.4 percent) assessed still demonstrated swallowing dysfunction (Barer, 1989).

The rate of swallowing impairment was related to the age of the patients at initial assessment: while 23 percent of those patients under age 70 were swallowing impaired, 36 percent of those over age 70 were. This was a significant difference (p<0.01). This difference disappeared by 1 week, however. The authors suggest that this may be due to the high mortality rate of the elderly patients with dysphagia, leading to a decrease in statistical power of the findings (Barer, 1989).

Smithard et al. (1997) followed 121 consecutive stroke patients admitted to a hospital within 24 hours of a stroke. They followed the patients for up to 180 days. At admission, 61 (51 percent) demonstrated a compromised swallow using a BSE method of assessment. At day 180, 8 out of 73 assessed (11 percent) demonstrated dysphagia. Overall, 6 cases out of 61 original cases (9.8 percent) were known to persist to 6 months. Some cases developed after the initial assessment (24 total); all but 2 were transient (Smithard, O'Neill, England et al., 1997; Smithard, O'Neill, Parks et al., 1996).

In conclusion, dysphagia is a symptom experienced by many stroke patients just after the event, occurring in 20 to 90 percent of patients, depending on the diagnostic methodology. It is impossible to determine which of these studies provides the most accurate rate, because, as mentioned before, dysphagia is not a defined disease, but a cluster of symptoms that may not occur all the time and the diagnosis of which may be influenced by subjective judgment of the clinician. A median of similar studies provides the best overall estimate: hospital studies using videofluoroscopy had a median diagnosis rate of 74.6 percent (Daniels, McAdam, Brailey et al., 1997). Those using BSE or a water swallow test had a median of 41.7 percent (Kidd, Lawson, Nesbitt et al., 1993). The difference between these two estimates is accounted for both by silent aspiration and physiologic dysfunction that may not affect the patient's health. If it were found that all of the cases of dysphagia diagnosed with videofluoroscopy caused significant disability to the patient, then it might be warranted to test all acute stroke patients for dysphagia. However, there is no evidence that this is the case.

Limited evidence suggests that dysphagia occurs more often in older stroke victims. It appears that hemispheric strokes are commonly characterized by dysphagia, despite commonly held beliefs that dysphagia usually occurs only after a brainstem stroke. Dysphagia is most often a transient symptom of acute stroke, with a large majority of cases spontaneously recovering within 6 months.

Epidemiology of dysphagia in Parkinson's disease

Seven studies were identified that analyzed the diagnosed occurrence of dysphagia or swallowing problems in patients with Parkinson's disease (see Evidence Table 5 for details on study characteristics and results). Study designs of particular interest were those that withheld levodopa therapy (L-dopa) during the day of dysphagia testing, and those that reported disease severity on widely used scales (such as Hoehn and Yahr). Estimates of the occurrence of dysphagia in patients with PD range from 23 to 81 percent. These rates may be affected by duration and severity of disease, whether patients were taking medication at the time of testing, and the method of measuring dysphagia. Most of these researchers examined patients with mild to moderate Parkinson's disease (stage 1 to 3 out of 5 on Hoehn and Yahr Scale). Three studies reported on the relationship between severity of illness and severity of dysphagia; two studies (Fuh, Lee, Wong et al. 1997; Wintzen, Badrising, Roos et al. 1994) reported no correlation when severity of disease was measured using the Hoehn and Yahr scale. One study (Coates and Bakheit, 1997) reported a strong correlation between both severity and length of illness and severity of dysphagia, when severity of illness was measured using the United Parkinson's Disease Rating Scale (UPDRS) to assess disease severity and the Chicago Assessment Scale to assess level of swallowing dysfunction.

Those researchers who measured dysphagia using videofluoroscopy (VFSS or MBS) (three studies) found rates of dysphagia varying from 63.2 to 81.1 percent (Bushmann, Dobmeyer, Leeker et al., 1989; Fuh, Lee, Wang et al., 1997; Wintzen, Badrising, Roos et al., 1994). Questionnaires (3 studies) yielded rates from 22.9 to 76.9 percent (Coates and Bakheit, 1997; Hartelius and Svensson, 1994; Singer, Weiner, and Sanchez-Ramos, 1992). Most researchers reported rates in the 60 to 80 percent range. The mean age and duration of illness seem comparable in most of these studies and thus probably do not affect the variation of the rates. However, whether the patients were receiving L-dopa at the time of the study may have affected results. It is unclear whether severity of swallow dysfunction correlates with severity of Parkinson's disease.

Because L-dopa appears to affect swallow function in some patients (Bushmann, Dobmeyer, Leeker et al., 1989; Fuh, Lee, Wang et al., 1997), it appears that the best study would test patients while not taking the medication. Two studies did this (Bushmann, Dobmeyer, Leeker et al., 1989; Fuh, Lee, Wang et al., 1997), and found rates of 75 percent and 63.2 percent in groups of 20 and 19 patients, respectively. Both used MBS. There is no apparent advantage to either of these studies, so the mean will be used in the calculation of burden of illness, 69.1 percent.

Epidemiology of dysphagia in Alzheimer's disease patients

One study was located that examined the prevalence of swallowing disorders in Alzheimer's patients (see Evidence Table 7 for details). Horner et al. (1994), in a prospective case series, examined 25 patients age 55 and over with moderate or severe Alzheimer's disease using videofluoroscopy. Twenty-one out of 25 patients (84 percent) showed some sort of swallowing abnormality on videofluoroscopy. Six of these patients with abnormalities showed evidence of aspiration (24 percent of all patients). The most prevalent abnormality was delayed reflex initiation, followed by hesitancy of oral preparation and deficient pharyngeal clearance (Horner, Alberts, Dawson et al., 1994). This study suggests that an overwhelming majority of Alzheimer's patients experience swallowing problems; however, it is only one study and included only a small patient pool. No evidence is available about the occurrence of dysphagia in patients with mild Alzheimer's disease; it is therefore currently not possible to determine if there is a correlation between severity of Alzheimer's disease and severity of dysphagia.

Multiple sclerosis

The onset of MS usually occurs between the second and fifth decades (McFarlin and McFarland, 1982a) but because of its slow, insidious progression over several years, many elderly also suffer from it. It is characterized by the idiopathic demyelination of the white matter of the central nervous system. When certain cranial nerves are affected by this demyelination, dysphagia will occur.

MS was recorded in 0.6 percent (600 per 100,000) of all nursing home admissions documented by the 1985 National Nursing Home Survey (Hing, Sekscenski, and Strahan, 1989). Three other studies were identified that examined prevalence of MS in the United States. Two of these studies were investigations of possible cluster areas of MS (Helmick, Wrigley, Zack et al., 1989; Hopkins, Indian, Pinnow et al., 1991), and therefore are not appropriate for determining a U.S. generalizable burden of illness.

In Olmstead County, Minnesota, Wynn et al. (1990) examined patient records of the Mayo Clinic records linkage system, and discovered a sex- and age-adjusted prevalence of 170.8 per 100,000 on prevalence date January 1, 1985. This rate was significantly higher for women (231.9) than for men (79.8). Of those age 65 and older, the overall prevalence was 265.7 per 100,000, again, higher for women (369.1) than for men (89.7) (Wynn, Rodriguez, O'Fallon et al., 1990). Even though the Mayo Clinic records are very thorough, these figures may not be generalizable to the entire population, because of a latitudinal gradient of MS prevalence that has been discovered in North America (McFarlin and McFarland, 1982b), in which more southern areas have higher rates.

We identified one study that examined the diagnosed occurrence of swallowing disorders in individuals with MS. Hartelius and Svensson (1994) sent a questionnaire to members of the Multiple Sclerosis section of the Association for the Neurologically Disabled in Sweden. A total 278 questionnaires was sent and 203 returned (response rate of 73 percent). Of respondents, 68 percent were females, consistent with the observation that women are at higher risk of MS than men (Wynn, Rodriguez, O'Fallon et al., 1990); 33 percent reported that mastication and swallowing were more difficult than prior to disease onset; 13 percent reported having difficulty swallowing liquid at least fairly often; 16 percent reported problems swallowing solids at least fairly often; and 27 percent reported choking on food or drink at least fairly often (Hartelius and Svensson, 1994). An overall prevalence rate of dysphagia was not possible to determine given the self-report nature of this study. The occurrence of dysphagia reported in this study may be unrealistically high because of self-selection bias.

Motor neuron disease

MND is a family of neurodegenerative diseases in which there is a selective progressive depletion of motor neurons (Kirshner, 1989). There are three common subtypes of MND: ALS, the most common type, involves both the upper and lower motor neurons of the pyramidal tracts; progressive muscular atrophy (PMA) is characterized by motor neuron depletion in the anterior horn of the spinal cord; and bulbar palsy (BP) mainly affects the lower cranial nerve nuclei (Leighton, Burton, Lund et al., 1994). Progression of this disease is rapid and therefore life expectancy is generally short (less than 5 years).

The epidemiology of motor neuron disease in the United States was investigated in one published study, and ALS specifically investigated in two others. Lilienfeld et al. (1991) examined hospital discharge data for a 5-year period in a large metropolitan area; the average annual age-adjusted incidence of MND was estimated at 6 per 100,000 in 1984, the most recent year covered. For individuals age 65 to 74, men showed an incidence of 25 per 100,000, and women, 18 per 100,000 (Lilienfeld, Sprafka, Pham et al., 1991). The prevalence rate of MND was not calculated. These incidence rate estimates may be low because of the focus on hospital discharges.

Two studies looking specifically at ALS reported annual incidence rates of 1.14 (Annegers, Appel, Lee et al., 1991) and 1.8 (McGuire, Longstreth, Koepsell et al., 1996) per 100,000. In both studies, women appeared to have a slightly lower incidence than men. Incidence rates were higher among the elderly; Annegers et al. (1991) reported that individuals age 75 and over had a rate of 4.01 per 100,000; McGuire et al. (1996) reported higher rates, at 7.18 per 100,000 men, and 5.54 per 100,000 women. The Annegers study results came from surveys of neurologists, many of whom refused participation; therefore, these rates may be unrealistically low.

We identified two published studies that investigated the diagnosed occurrence of swallowing disorders in MND. Reported dysphagia rates were 51.1 percent (Leighton, Burton, Lund et al., 1994) and 71 percent (Mayberry and Atkinson, 1986). Dysphagia rates for ALS reported by Leighton were 29 percent; this study is likely superior to that of Mayberry et al. because it does not suffer from self-selection bias as a result of survey methods.

Progressive supranuclear palsy

PSP is often mistaken for Parkinson's disease because of its Parkinsonian symptom characteristics. It has a late middle-age onset, and is characterized by a high density of neurofibrillary tangles and neuropil threads in the basal ganglia and brainstem (Litvan, Agid, Calne et al., 1996). Symptoms include bradykinesia and rigidity, severe gait difficulty, and pseudobulbar signs. It progresses more rapidly than Parksinson's disease (Golbe, Davis, Schoenberg et al., 1988) and does not generally respond to L-dopa treatment. Onset of these symptoms has been reported to begin at a mean age between 55 and 70 years (Litvan, Agid, Calne et al., 1996).

Two studies were located that examined incidence or prevalence of PSP; Golbe et al. (1988), in a survey and exam, determined a prevalence rate of 1.39 per 100,000 (Golbe, Davis, Schoenberg et al., 1988). Bower et al. (1997), using the Mayo Clinic records linkage system, calculated an annual incidence rate of 1.1 per 100,000; this rose to 5.3 per 100,000 for those age 50 and older (Bower, Maraganore, McDonnell et al., 1997). These are the only two studies we found in the published literature on PSP, and they are not comparable given that one study calculated prevalence and one calculated incidence.

The most frequent cause of death in PSP is pneumonia (Litvan, Agid, Calne et al., 1996); therefore, determination of the occurrence and characteristics of swallowing problems is important. Litvan et al. (1997) assessed 27 patients with PSP using a swallowing questionnaire and ultrasound imaging of swallowing. Results indicated that all PSP patients had at least one swallowing complaint; 15 (55.6 percent) complained of difficulty swallowing-5 had more difficulty swallowing solids than liquids, and 10 had more difficulty with liquids than solids. Five (19 percent) demonstrated aspiration (Litvan, Sastry, and Sonies, 1997). This was the only published study identified that investigated swallowing problems in PSP patients.

Huntington's disease

Huntington's disease is a hereditary neurodegenerative disease affecting the basal ganglia, causing movement disorders, dementia, and emotional impairment (Kagel and Leopold, 1992; Leopold and Kagel, 1985). Dysphagia is very common in these patients, characterized by lack of control of the rate of food intake, difficulty with liquids, bolus retention in the buccal recesses, and choking. Many of these problems are side effects of cognitive impairment rather than directly the result of neurologic or neuromuscular dysfunction, per se (Leopold and Kagel, 1985).

One study was located that examined the prevalence and incidence of Huntington's disease in a U.S. population. Kokmen et al. (1994), at the Mayo Clinic, examined records from 1950 to 1990 and identified 10 definite cases of Huntington's disease. The prevalence on January 1, 1990 was 1.9 per 100,000 overall (1.8 for women and 2.0 for men). The average annual incidence rate between 1970 and 1989 was 0.2 per 100,000 (0.3 for women and 0.1 for men) (Kokmen, Ozekmekci, Beard et al., 1994).

One study examined the diagnosed occurrence of dysphagia in Huntington's disease; Kagel and Leopold (1992) examined 35 patients with Huntington's disease (mean age 45.5) using a clinical questionnaire, assessment of feeding, and videofluoroscopic exam. Twenty-seven patients (80 percent) coughed or choked on both solids and liquids; six were symptomatic with food only, and two with liquid only. Thus, 100 percent of patients with Huntington's disease showed dysphagia of one kind or another. In the hyperkinetic variant of Huntington's disease (30 of 35 patients), 29 (96.7 percent) demonstrated oral dysphagia, 27 (90 percent) pharyngeal dysphagia, and 11 (36.6 percent) esophageal dysphagia during clinical assessment. A total of 100 percent of hypokinetic-Huntington's disease patients (five patients) demonstrated oral and pharyngeal swallowing dysfunction; none demonstrated esophageal dysphagia (Kagel and Leopold, 1992). Selection methodology of these patients was not described; therefore, there is a possibility that the researchers specifically selected patients with dysphagia for study.