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Rademaker et al.:
Age and Volume Effects
275
Journal of Speech, Language, and Hearing Research
Alfred W. Rademaker
Northwestern University
Chicago, IL
Barbara Roa Pauloski
Northwestern University
Evanston, IL
Laura A. Colangelo
Northwestern University
Chicago, IL
Jeri A. Logemann
Northwestern University
Evanston, IL
Understanding the nature of swallowing in persons without swallowing problems
is a prerequisite to evaluating the nature and extent of dysphagia in persons with
compromised swallowing. In order to determine how swallowing varies with age
and with liquid bolus volume in women, we assessed 167 normal female
swallowers videofluoroscopically and obtained multiple measures of swallowing
function. The women in this study demonstrated a change in swallowing function
with age, due primarily to an increase in pharyngeal transit and total duration of
the motor response. The duration of closure and opening of valves in the upper
aerodigestive tract also increased with age, and the duration of laryngeal
elevation and hyoid movement peaked in the 60–79-year-old age groups. Bolus
volume effects were quite consistent across most measures. As the bolus volume
increased from 1 ml to 10 ml, transit times decreased and durations of valve
closure and opening increased. The results of this study may be used to specify
the relationship of swallowing function to age and liquid bolus volume in women,
relationships that heretofore have been observed only in part and in smaller and
more heterogeneous populations.
KEY WORDS: normal swallowing, viscosity and volume effects, fluoroscopy,
age effects, women
Age and Volume Effects on Liquid
Swallowing Function in Normal
Women
JSLHR
, Volume 41, 275–284, April 1998
©1998, American Speech-Language-Hearing Association 1092-4388/98/4102-0275
Journal of Speech, Language, and Hearing Research
275
U
nderstanding the nature of swallowing in persons without swal-
lowing problems is a prerequisite to evaluating the nature and
extent of dysphagia in persons with compromised swallowing.
Variables that have been related to swallowing function in normal swal-
lowers include age, gender, bolus type (bolus vs. dry swallow), liquid
bolus volume, and bolus consistency. Normal swallowing has been as-
sessed using different techniques (e.g., videofluoroscopy, manometry),
each resulting in multiple measures of swallowing function.
Studies of age effects on swallowing function in normal swallowers
have demonstrated that older individuals exhibited extended oropha-
ryngeal pressure waveforms as measured by manometry (Perlman,
Schultz, & VanDeale, 1993; Shaker et al., 1993). As seen in simulta-
neous videofluoroscopy and manometry, older persons had slower swal-
lowing in general (Robbins, Hamilton, Lof, & Kempster, 1992) as well as
a trend toward a shorter interval between the onset of vocal cord adduc-
tion and onset of upper esophageal sphincter relaxation (Ren et al., 1993).
On ultrasound, the duration of dry and wet swallows was observed to
increase with age (Sonies, Parent, Morrish, & Baum, 1988) and peak
suction pressure reduced with age (Nilsson, Ekberg, Olsson, & Hindfelt,
1996). Although much prior work supports the slowing of swallowing
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JSLHR
, Volume 41, 275–284, April 1998
Journal of Speech, Language, and Hearing Research
with age, Tracy et al. (1989), using videofluoroscopy,
observed mixed results in that oral transit time and
duration of pharyngeal response decreased with age
whereas pharyngeal swallow delay increased with age.
Several investigators have documented systematic
changes in normal swallowing with increasing volume
of a liquid bolus. As liquid bolus volume increased from
1 ml to 5 ml, the durations of laryngeal closure and
cricopharyngeal opening were seen to increase and the
duration of tongue base contact to the posterior pharyn-
geal wall decreased (Lazarus et al., 1993). Systematic
changes in epiglottic and laryngeal movement with in-
creasing bolus size have been supported in measures
taken from biomechanical analysis (Logemann et al.,
1992). Increasing bolus volume has been shown to pro-
long the period during which the oropharynx is
reconfigured to swallow, yet the period of pharyngeal
clearance remains constant, resulting in more rapid
bolus expulsion (Kahrilas, Lin, Chen, & Logemann,
1996; Kahrilas & Logemann, 1993). Longer durations
of cricopharyngeal opening have been observed at larger
liquid bolus volumes (Ohmae, Logemann, Kaiser,
Hanson, & Kahrilas, 1995).
The purpose of this study was the documentation of
swallowing function in a large sample of women with
no swallowing disorders in order to provide normative
data for comparison with other populations. Variation
in swallowing function by age group and by liquid bolus
volume was also investigated.
Methods
Subject Recruitment
Normal volunteers were actively recruited through
advertisements for swallowing studies over the period
1991 through 1996. These persons had no history of a
swallowing problem or of any diseases, illnesses, medi-
cations, or surgeries involving the central nervous sys-
tem, gastrointestinal tract, or head and neck region, that
might affect swallowing. A total of 167 women were in-
cluded in this study. The study protocol was approved
by the Institutional Review Board of Northwestern Uni-
versity. The age distribution of the study sample is given
in Table 1. Women between the ages of 21 and 50 were
provided with pregnancy tests prior to study participa-
tion. Women between 21 and 50 years of age who re-
ported that they had a hysterectomy or were post meno-
pausal were exempt from the pregnancy test.
Data Collection and Reduction
Collection and reduction of swallowing data followed
the procedures described in Logemann (1993). Each
person’s swallowing function was examined once, using
videofluoroscopy in the lateral projection. Fluoroscopic
data were recorded on 3/4 inch videotape at 30 frames
per second. The fluoroscopy tube was focused on the lips
anteriorly, the posterior pharyngeal wall posteriorly, the
soft palate superiorly, and the bifurcation of the esopha-
gus and airway inferiorly. The swallowing protocol in-
cluded two swallows each of 1 ml, 3 ml, 5 ml, and 10 ml
liquid barium (50% liquid barium sulfate suspension and
50% room temperature water). The order of bolus vol-
ume administration used for these normal subjects was
the same order as our standard protocol for patients with
swallowing problems. Bolus volume proceeds from low
to high in patients to minimize the risk of aspiration of
large volumes (Dodds, Stewart, & Logemann, 1988). In
previous work (Lazarus et al. 1993), we did not observe
order effects in multiple swallows at the same volume.
Using a SONY U-matic VCR with frame-by-frame
and slow-motion analysis capabilities, videoframes on
which the bolus reached specific points in the orophar-
ynx and on which particular structural movements be-
gan and ended were identified. From these observations,
the following measures were made:
1. Oral transit time: the time interval in seconds from
onset of tongue movement propelling the bolus pos-
teriorly until the bolus head passes the ramus of
the mandible;
2. Pharyngeal transit time: the time interval in sec-
onds from the bolus head passing the ramus of the
mandible until the bolus tail passes through the
cricopharyngeal sphincter;
3. Pharyngeal delay time: the time interval in seconds
from the bolus head passing the ramus of the man-
dible until the onset of laryngeal elevation;
4. Pharyngeal response time: the time interval in sec-
onds from the onset of laryngeal elevation until the
bolus tail passes through the cricopharyngeal
sphincter;
5. Duration of velopharyngeal (VP) closure: the time
interval in seconds from the first to last contact of
the soft palate with the posterior pharyngeal wall;
6. Duration of laryngeal closure: the length of time in
seconds that the laryngeal entrance between the
arytenoid and base of epiglottis was closed in the
Table 1. Age distribution of the study sample of 167 women.
Age in years Number Percent
20–39 61 37%
40–59 45 27%
60–79 38 23%
80–89 23 13%
Total 167 100%
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Rademaker et al.:
Age and Volume Effects
277
Journal of Speech, Language, and Hearing Research
lateral plane during the swallow;
7. Duration of cricopharyngeal (CP) opening: the
length of time in seconds that the cricopharyngeal
region was open during each swallow;
8. Duration of hyoid movement in seconds: the time
interval in seconds between start of movement and
return to rest of the hyoid bone;
9. Duration of laryngeal elevation in seconds: the time
interval in seconds between the beginning of laryn-
geal elevation and laryngeal return to rest.
Inter- and intra-observer reliability of the above tem-
poral measures was at least .82 and .98, respectively
(Logemann et al., 1995). In addition, the presence or
absence of oral residue and pharyngeal residue was ob-
served from the videofluoroscopic studies. A summary
measure, oropharyngeal swallow efficiency (OPSE), was
calculated as the percent of bolus swallowed divided by
the total oral and pharyngeal transit time (Rademaker,
Pauloski, Logemann, & Shanahan, 1994).
Statistical Analyses
The main objective of the statistical analyses was
to determine age and volume differences in means.
Mixed (fixed and random effects) model analysis of vari-
ance was used to determine age and volume differences
(Searle, 1971), with age group and bolus volume as fixed
effects and persons within age group as random effects.
A two-way analysis of variance was used, with age group
as the between-person factor (four age categories: 20–
39, 40–59, 60–79, 80–89), and bolus volume as the
within-person factor (1 ml, 3 ml, 5 ml, 10 ml). This analy-
sis provided a statistical test for age by volume interac-
tion. If the test for interaction was not significant (p >
0.05), and if the main effect for age group (or bolus vol-
ume) was significant (p < 0.05), then Tukey’s multiple
comparison procedure at the .05 level was used to com-
pare means across age groups (or bolus volumes). If the
test for interaction was significant, then subgroup main
effect tests were done, but not multiple comparisons.
Individual swallows were kept distinct in the analysis.
Statistical analyses were done using PROC MIXED in
SAS (SAS Institute, 1992). Separate variances were as-
sumed for each age group, and compound symmetry was
assumed across bolus volumes. No formal statistical
analyses were performed on the observation of residue.
Results
Age Group by Bolus Volume Interactions
The test for age by volume interaction examines
whether the pattern of means across age groups is simi-
lar for the four bolus volumes. Table 2 gives the results
of the test for interaction. The following measures showed
no significant age group by bolus volume interaction (in-
teraction p > .05): oral transit time, pharyngeal transit
time, pharyngeal delay time, OPSE, duration of VP clo-
sure, duration of CP opening, and duration of hyoid
movement. For these measures, the pattern of varia-
tion of means across age groups was similar for the four
bolus volumes, and data were pooled over the four bolus
volumes for statistical testing. Figures 1 and 2 display
plots of mean levels by age group for these measures.
Certain measures demonstrated a significant age
group by bolus volume interaction. These were: pharyn-
geal response time, duration of laryngeal closure and
duration of laryngeal elevation. For these measures, the
pattern of variation of means across age groups depended
on bolus volume, and data were analyzed separately by
bolus volume. Figure 3 displays plots of volume-specific
mean levels by age group for these measures.
Age Effects
Table 2 reports the p-values for the main effect of
age. There were no age differences for oral transit time
(Figure 1, Panel A). Six measures with non-significant
interactions had a significant age effect (p < .05). There
was a significant increase in pharyngeal transit time
with age with older age groups demonstrating longer
times than younger groups (Figure 1, panel B). Although
pharyngeal delay time varied significantly by age (Fig-
ure 1, Panel C), there was no systematic increase across
age groups. OPSE decreased with age (Figure 1, Panel
D), with the 60–79 and 80–89 year groups having the
lowest values. The duration of VP closure (Figure 2,
Panel A) and the duration of CP opening (Figure 2, Panel
B) increased significantly with age, with the two oldest
Table 2.
p
-values for the test of age by volume interaction, and for
the tests of the age and volume main effects.
Age Volume
Measure Interaction effect effect
Oral transit time ns* ns <0.001
Pharyngeal transit time ns <0.001 0.004
Pharyngeal delay time ns 0.003 <0.001
Pharyngeal response time 0.002 n/a** n/a
Oropharyngeal swallow efficiency ns 0.006 <0.001
Duration of velopharyngeal closure ns <0.001 <0.001
Duration of laryngeal closure 0.001 n/a n/a
Duration of cricopharyngeal opening ns <0.001 <0.001
Duration of hyoid movement ns <0.001 ns
Duration of laryngeal elevation 0.001 n/a n/a
*ns: not significant (
p
> 0.05)
**n/a: not applicable since the test for interaction is significant (
p
<
0.05).
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JSLHR
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Journal of Speech, Language, and Hearing Research
age groups having longer durations than the younger
groups. For the duration of hyoid movement (Figure 2,
Panel C), the 60–79 year age group had higher levels
than all other age groups.
Pharyngeal response time differed significantly by
age for all bolus volumes (Figure 3, Panel A). The dura-
tion of laryngeal closure differed significantly by age for
bolus volumes at or above 3 ml (Figure 3, Panel B). The
Figure 1. Mean (± sem) of measures of swallowing function (vertical axis) by age group (horizontal axis). Measures are: Panel A: oral transit
time (in seconds); Panel B: pharyngeal transit time (in seconds); Panel C: pharyngeal delay time (in seconds); Panel D: oropharyngeal
swallow efficiency.
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Rademaker et al.:
Age and Volume Effects
279
Journal of Speech, Language, and Hearing Research
duration of laryngeal elevation differed significantly by
age for all bolus volumes (Figure 3, Panel C). All three
of these measures demonstrated their highest levels for
the 60–79 year age group.
Bolus Volume Effects
Most measures with a non-significant interaction
had a significant volume effect (Table 2). Figures 4 and
5 display plots of mean levels by bolus volume for these
Figure 2. Mean (± sem) of measures of swallowing function (vertical axis) by age group (horizontal axis). Measures are: Panel A: duration of
velopharyngeal (VP) closure (in seconds); Panel B: duration of cricopharyngeal (CP) opening (in seconds); Panel C: duration of hyoid
movement (in seconds).
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measures. Oral transit time decreased significantly as
bolus volume increased (Figure 4, Panel A), as did pha-
ryngeal transit time (Figure 4, Panel B) and pharyn-
geal delay time (Figure 4, Panel C). The mean OPSE
levels for the 5 ml and 10 ml bolus volumes were signifi-
cantly higher than for the 1 ml volume (Figure 4, Panel
D). The duration of VP closure (Figure 5, Panel A) and
the duration of CP opening (Figure 5, Panel B) increased
with increasing bolus volume. There were no differences
across volume in the duration of hyoid movement (Fig-
ure 5, Panel C).
For measures with a significant age by volume in-
teraction, significant differences were seen across bolus
volume for the two oldest age groups for pharyngeal re-
sponse time (Figure 3, Panel A) and for the duration of
laryngeal elevation (Figure 3, Panel C). The duration of
laryngeal closure demonstrated significant volume dif-
ferences for all age groups (Figure 3, Panel B).
Oral and Pharyngeal Residue
The 167 women in this study provided a total of 1435
swallows. Oral residue was seen in 215 swallows (15.0%)
and pharyngeal residue was seen in 427 swallows
(29.8%). Table 3 summarizes the percent of swallows on
which oral residue or pharyngeal residue was observed,
by age group and bolus volume. Oral and pharyngeal
residue occurred least frequently in the 20–39-year
Figure 3. Mean (±sem) of measures of swallowing function (vertical axis) by age group (horizontal axis), and 1 ml (dotted line), 3 ml (dashed
line), 5 ml (dashed and dotted line), and 10 ml (solid line) bolus volume. Measures are: Panel A: pharyngeal response time (in seconds);
Panel B: duration of laryngeal closure (in seconds); Panel C: duration of laryngeal elevation (in seconds).
Table 3. Percent of swallows with oral residue and pharyngeal
residue, by age group and by bolus volume.
Number of Percent with Percent with
swallows oral residue pharyngeal residue
Age group
20–39 517 10.1 18.0
40–59 374 15.8 37.4
60–79 328 12.5 34.1
80–89 216 29.2 38.0
Bolus volume
1 ml 378 5.0 18.0
3 ml 354 13.8 27.4
5 ml 355 16.1 34.4
10 ml 348 25.9 40.2
group and most frequently in the 80–89-year group. The
occurrence of both oral and pharyngeal residue increased
as bolus volume increased.
Discussion
This study represents a large set of normative data
for women, where swallowing has been assessed by
videofluoroscopy, a widely used procedure for assessing
swallowing function in the clinical setting. These data
form a basis for the comparison of women with normal
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Rademaker et al.:
Age and Volume Effects
281
Journal of Speech, Language, and Hearing Research
Figure 4. Mean (±sem) of measures of swallowing function (vertical axis) by bolus volume (horizontal axis). Measures are: Panel A: oral
transit time (in seconds); Panel B: pharyngeal transit time (in seconds); Panel C: pharyngeal delay time (in seconds); Panel D: oropharyngeal
swallow efficiency.
swallowing function to other populations. Similar analy-
ses are in progress to compare women with men. In our
current research, data are being collected for compari-
sons of swallowing function in male and female patients
with head and neck cancer. Comparisons of the liquid
bolus also should be made with more viscous bolus types.
Using scintigraphy in normal subjects, swallowing abil-
ity, as measured by oral discharge time, residue and ef-
ficiency, were different with a viscous than with a liquid
bolus (Hamlet et al., 1996).
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Figure 5. Mean (±sem) of measures of swallowing function (vertical axis) by bolus volume (horizontal axis). Measures are: Panel A: duration
of velopharyngeal (VP) closure (in seconds); Panel B: duration of cricopharyngeal (CP) opening (in seconds); Panel C: duration of hyoid
movement (in seconds).
The women in this study demonstrated differences
in swallowing function with age. These differences could
be characterized as prolongation of bolus transit time
through the oropharynx and prolongation of valve closure
(velopharynx, larynx) or opening (cricopharyngeus). These
differences may relate to slowing of neural processing time
with aging. Slowing of swallowing function with age has
been indicated in past studies. Specifically, Sonies et al.
(1988) found that “the older subjects’ swallows were gen-
erally slower than those of younger subjects” (p. 5), and
that age-related increases in hyoid motion times were
more striking for women than for men. Robbins et al.
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Rademaker et al.:
Age and Volume Effects
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Journal of Speech, Language, and Hearing Research
(1992), observing significant age-related increases in
bolus transit durations in a mixed population of men
and women, also concluded that “as people get older,
they swallow more slowly” (p. 827). Our data support
these prior studies in that pharyngeal transit time in-
creased with age, as did the durations of VP closure and
CP opening. Moreover, the frequency of bolus residue
also increased with age. Our summary OPSE, which is
100 when the complete bolus passes though the oral
cavity and pharynx in 1 second, decreased from 100 in
our youngest age group to 90 in the oldest age group.
Since the amount of residue in this population is typi-
cally very small, it is unlikely that residue per se plays
a major role in this decrease in OPSE. In perspective,
this age-related decrease in OPSE in these women with-
out swallowing problems is relatively small and should
not be given undue importance, especially when com-
pared to changes seen in persons with dysphagia. For
example, OPSE averaged between 40 and 50 during one
year of follow-up for surgically treated oral and oropha-
ryngeal cancer patients (Pauloski et al., 1994).
Whereas some of our measures clearly support the
observation of slower swallowing with age, other measures
do so only indirectly. The components of pharyngeal tran-
sit, namely pharyngeal delay and response, do not dem-
onstrate monotone increases with age (consistent increase
rather than fluctuation), yet when added together to con-
stitute pharyngeal transit time, clear increases with age
are seen. The durations of laryngeal closure and laryn-
geal elevation peak in the 60–79 age range, then decrease
in the oldest age group, rather than exhibiting monotone
increases with age. Tracy et al. (1989), using the same
assessment techniques as we used, demonstrated signifi-
cant decreases in the duration of pharyngeal response with
age, but observed no significant age difference in the du-
ration of laryngeal closure. The total sample size in the
Tracy et al. study was 24, and the gender distribution
was not specified. Both our study and the Tracy et al. study
indicate that measures such as the durations of pharyn-
geal response or laryngeal closure may not follow the ex-
pected monotone age pattern.
Other studies of pressure measures showed effects
of aging on oral suction pressure and pharyngeal pres-
sure measures generated during swallow. Nilsson et al.
(1996) documented that elderly subjects had lower peak
suction pressure when sucking from a straw, and lower
swallowing capacity. Perlman et al. (1993) noted consis-
tent differences between young and old healthy subjects
in all pharyngeal pressure measures. These differences
indicated that the elderly had higher pressures, longer
waveforms, and longer durations on their pressure wave-
forms. Shaker et al. (1993) observed greater amplitudes
of pharyngeal peristalsis in the elderly, whereas age dif-
ferences in peristaltic durations depended on the site of
manometric pharyngeal measurement.
Bolus volume effects in the present study were quite
consistent across most measures. As bolus volume in-
creased from 1 ml to 10 ml, transit times decreased and
durations of valve opening and closure increased. As
bolus volume increases, the bolus head is positioned
more posteriorly in the oral cavity at the beginning of
swallowing and less time is required for the bolus to
traverse the same distance (Tracy et al., 1989). The Tracy
et al. study observed significant decreases in oral tran-
sit time as volume increased.
Increases across bolus volume for duration of laryn-
geal closure and duration of CP opening as observed in
our study were consistent with those seen in 10 normal
volunteers by Lazarus et al. (1993). Logemann et al.
(1992) also observed increased duration of laryngeal clo-
sure, as measured by biomechanical analysis, as bolus
volume increased, in 8 normal male subjects. Kahrilas
and Logemann (1993) have described the effect of liquid
bolus volume on swallowing function in men. With vol-
ume increase, the reconfiguration of the oropharynx from
an airway passage to a swallow pathway occurs earlier
for larger volumes. This results in longer durations of
VP closure, laryngeal closure, and CP opening. On the
other hand, Ren et al. (1993), using a combination of
measurement techniques including videoendoscopy, ob-
served a non-significant increase in the duration of vo-
cal fold adduction as bolus volume increased from a dry
swallow to a 20 ml liquid bolus. Our present study ex-
amined airway entrance closure, not vocal fold closure.
Comparisons of our results with previous investi-
gations allow some generalizations to be made despite
the fact that results may vary because of differences in
measurement technique and heterogeneity of study
populations. Older individuals exhibit a slowing of swal-
lowing, as observed by videofluoroscopic, manometric,
and ultrasonic evaluation techniques. Larger liquid bo-
lus volumes exhibit a prolongation of valve closure and
opening, as observed by videofluoroscopy and video-
endoscopy. The results of this study may be used to
clarify the relationship of swallowing function to age and
liquid bolus volume in women, relationships that here-
tofore have been observed only in part in smaller and
more heterogeneous populations. It is our goal to con-
tinue these types of analyses to characterize swallow-
ing function by age, for women and men, by liquid bolus
volume, and by other non-liquid bolus consistencies.
Acknowledgment
This research was funded by NIH/NCI P01 CA40007.
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Received February 25, 1997
Accepted November 5, 1997
Contact author: Alfred W. Rademaker, PhD, 680 North Lake
Shore Drive, Suite 1104, Chicago, IL 60611.
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