Journal of Behavioral and Brain Science, 2011, 1, 12-15
doi:10.4236/jbbs.2011.11003 Published Online February 2011 (http://www.SciRP.org/journal/jbbs)
Salivary Alpha-Amylase Reactivity under
Psycho-Physiological Stress. A Nonverbal
Communication Measurement Tool?
Takuji Inagaki1, Masa Ieda2, Satoko Yamashita2, Tsuyoshi Miyaoka2, Jun Horiguchi 2
1Shimane Universi t y, Faculty of Education, Department of Psychol o gy an d Special Support Educ ati o n,
Nishikawatsu, Matsue, Shimane, Japan
2Shimane Universi t y, Faculty of Medi ci ne, Department of Psychiatry, Shimane, Japan
Received January 25, 2011; revised February 12, 2011; accepted February 17, 2011
Abstract
Previous studies have shown that changes in salivary alpha-amylase (sAA) levels are dependent on psycho-
social stress stimulation and reflect the activity of the sympathetic nervous system. sAA measurement can be
performed easily and quickly; therefore, it may be useful for evaluating psychosocial or physical stress. The
aim of this preliminary study was to examine the use of sAA measurements as objective indicators of psy-
chosocial and/or physical stress levels by examining sAA changes in volunteers subjected to conditions
similar to those suffered by children with severe motor and intellectual disabilities and cerebral paralysis.
Twelve healthy volunteers were required to not move or speak, as is found in patients suffering from total
paralysis, for 30 min. Saliva samples were taken at three points, and sAA activity was measured using a
hand-held monitor before the test, immediately after the test, and 10 min after the test. In the present study, a
marked increase in sAA activity due to physiological stress and a rapid return to the baseline level were ob-
served. Many subjects felt body pain and mental distress. This measurement method is useful for evaluating
stress in children with severe motor and intellectual disabilities, who can not fully express their emotions or
communicate with their caregivers.
Keywords: Nonverbal Communication, Psychosocial Stress, Physical Stress, Salivary Alpha-Amylase, Se-
vere Motor and Intellectual Disabilities
1. Introduction
Salivary alpha-amylase (sAA) has been suggested to
reflect stress-related body changes. Psychosocial stress
increases the release of salivary alpha-amylase, which
reflects the activity of the sympathetic-adrenal-medullary
(SAM) system [1-3]. Therefore, it is supposed that sAA
measurement is a useful tool for evaluating the SAM
system. In addition, previous studies examining the re-
sponse of sAA levels to SAM system activity showed
that increased sAA levels were correlated with increased
plasma catecholamine, indicating sympathetic nervous
system activation [4,5]. To date, numerous studies have
shown that changes in sAA levels are dependent on
stress stimuli [1,6-10].
As far as we know, few studies have investigated
psychosocial or physical stress in children with severe
motor and intellectual disabilities such as patients with
severe cerebral palsy. Such patients usually can not fully
communicate with others or describe their emotions. It is
therefore difficult to objectively evaluate their emotional
and physical state. sAA measurement can be performed
easily and quickly, and therefore, could be used to aid
the evaluation of the psychosocial and/or physical stress
levels of such patients.
In special support education, it is very important to be
able to evaluate and understand the level of psychosocial
and/or physical stress (distress) experienced by a child,
particularly in children with severe motor and intellectual
disabilities. The measurement of sAA is expected to be
useful as a nonverbal communication procedure for chil-
dren with severe motor and intellectual disabilities.
The aim of this preliminary study was to examine the
use of sAA measurements as objective indicators of

T. INAGAKI ET AL.
13
psychosocial and physical stress levels by examining
sAA changes in volunteers subjected to conditions simi-
lar to those suffered by children with severe motor and
intellectual disabilities and cerebral paralysis; i.e., the
participants were ordered to lie down with their face
pointing upward and to not move or speak for thirty
minutes.
2. Methods
The study subjects were recruited at Shimane University.
Twelve healthy student volunteers (mean age: 20.8  1.8
years; 7 females; 5 males) were recruited from the De-
partment of Psychology and Special Support Education
at the university. All subjects gave their written informed
consent before participating in this study after the pur-
pose and procedure had been fully explained to them.
All subjects were medication-free and had no history of
neurological or psychiatric disorders and drug/alcohol
abuse. They were also not taking any medication or
cigarette. We excluded the subjects with cardiovascular
diseases that caused autonomic dysfunction, chronic dis-
eases such as cancer or diabetes mellitus or hyperlipide-
mia. The subjects were told to refrain from brushing their
teeth or eating for at least 60 min before the measure-
ment session [8]. Using the previously developed method,
one-time saliva sampling collection was conducted dur-
ing the same time interval (2:00-3:00 PM) to minimize
any effects of circadian rhythms.
3. Results
We used a hand-held monitor (Nipro Co., Japan) and
reagent paper to measure enzymatic sAA activity. This
measurement method can be performed easily and
quickly and is a convenient and useful objective indica-
tor for medical and educational practice. The hand-held
monitor consisted of a disposable test strip and a monitor
[11,12]. This method for analyzing sAA has previously
been evaluated and used [13,14].
To assess autonomic functional changes, resting heart
rate (HR) was measured in all subjects during the same
time interval whilst they were lying in a recumbent posi-
tion, as heart rate is thought to be an indicator of auto-
nomic (sympathetic and parasympathetic) function.
The test consisted of three periods in which the sub-
jects remained in a recumbent position: 10 min resting
time (pre-test), 30 min fixed position time (test), and 10
min resting time (post-test). The subjects rested in a re-
cumbent position on the floor for 10 min before the main
part of the test. Then, they were required to not move or
speak, as is seen in patients suffering from total paralysis,
for 30 min. They remained in the fixed position, alert,
and quiet for 30 min. Then, they were ordered to remain
lying down and rest for a further 10 min.
In addition, all subjects were asked whether they were
experiencing any body pain or mental distress. Their pain
and mental distress were estimated using a VAS (visual
analogue scale). The VAS score was obtained from sub-
jects who felt body pain in some body portion or mental
distress at the end of the test. Subjects reported the level
of pain and mental distress as VAS score.
Saliva samples were taken before the test, after the
subjects had been lying in the fixed position for 30 min,
and at 10 min after the test. Heart rate was simultane-
ously measured in all subjects at the three time points.
The results are expressed as means  SD. To compare
the clinical variables at the three time points, the data were
analyzed with repeated measures ANOVA by applying the
SNK correction using Statview 5.01 (SAS Institute Inc.,
USA). The level of significance was set at p < 0.05.
The volunteers’ mean pre-test, test, and post-test sAA
levels were 32.2  16.6 (kU/l) (range, 17-69), 61.5 
47.2 (range, 24-193), and 34.9  11.8 (range, 18-56),
respectively. Significant differences were found using
the ANOVA among three points (F = 4.88, p = 0.018),
therefore, SNK correction was conducted. There were
significant differences between the test and pre-test sAA
levels (p < 0.05), and between the test and post-test sAA
levels of (p < 0.05). The salivary alpha-amylase level
increased significantly during the fixed positioning pe-
riod and had returned to the baseline by 10 min after the
test (Figure 1).
The mean pre-test, test, and post-test heart rates were
64.8  11.7, 63.5  8.3, and 61.2  10.4, respectively. In
contrast, heart rate did not change between the stress and
the rest conditions (Table 1). Ten subjects (77%) com-
plained of body pain, particularly in the head, lumbar,
hands, and heel. The mean VAS score of them for pain
Figure 1. Changes in salivary alpha-amylase activity after
remaining in a fixed position for 30 mins.

14 T. INAGAKI ET AL.
Table 1. Psycho-physiological stress test results.
Time (min)
0
(Pre-test)
30
(Test)
40
(Post-test)
Salivary alpha-amylase
(kU/L) 32.2 ± 16.6 61.5 ± 47.2* 34.9 ± 11.8✝
Heart rate 64.8 ± 11.7 63.5 ± 8.3 61.2 ± 10.4
*p < 0.05; Pre-test v.s. Test ✝p < 0.05; Test v.s. Post-test
was 54. Mental distress was revealed in five subjects
(38%) and the mean VAS score of them for mental dis-
tress was 63.
4. Discussion
In the present study, a marked increase in sAA activity
due to physiological stress was observed during the main
part of the test followed by a rapid return to the baseline
level. Many subjects felt body pain and mental distress.
A portable sAA activity monitor has recently been
developed, and several investigations have suggested that
sAA reflects mental stress or have shown a positive rela-
tionship between the sAA increases and sympathetic
activity.
Nater et al. [8] reported a positive relationship be-
tween the sAA level and sympathetic tone, which was
assessed using heart rate variability parameters during
periods of stress. Previous reports have also indicated
that the sympathetic nervous system plays a predominant
role in the sAA secretion observed under psychosocial
stress [2,3]. Several reports have demonstrated that psy-
chosocial stress increases the release of sAA and that a
marked increase in sAA occurs following exposure to
psychosocial stress, indicating that sAA activation is
stress-dependent.
Shirasaki et al. [5] reported that sAA was significantly
correlated with the VAS pain scale in patients with
chronic pain. In addition, after pain therapy (epidural
block), sAA activity was reduced in combination with a
decrease in pain intensity but not SAM activity. There-
fore, they suggested that sAA reflects the activity of the
SAM system during pain-induced stress and that sAA
measurements might be a good index for the objective
assessment of pain intensity.
In psychiatric patients, we previously reported that the
sAA activity of schizophrenic patients was significantly
higher than that of control subjects, and the correlation
between sAA level and psychiatric symptoms was highly
significant [15].
These findings suggest that sAA correlates with psy-
chiatric or/and psychosocial stress intensity.
To the best of our knowledge, only one study has
proposed using biochemical measurements of sAA activ-
ity as a non-verbal communication method for interact-
ing with children with severe motor and intellectual dis-
abilities [13]. The physiological conditions of these chil-
dren were evaluated by measuring their sAA activity,
which required the daily insertion and removal of tra-
cheostomy tubes or gastric tubes, and sAA was measured
before and after medical care. As a result, they found that
sAA activity was increased after medical care.
We performed the present study as a preliminary in-
vestigation aimed at clarifying whether this method
could be used in clinical practice to evaluate the levels of
psychosocial and/or physical stress in children with se-
vere and intellectual disabilities, who are not able to
move or complain about discomfort and/or distress. Such
children can not move their bodies for themselves and
may feel distress and pain when their body position is
changed by assistance.
In this study, we examined the changes in the sAA
levels of healthy volunteers subjected to conditions that
were designed to reflect those experienced by children in
the cerebral paralytic state, as it was impossible to di-
rectly examine the disabled children in fixed position for
long time. There are no studies which examine the stress
marker in the long-period fixed body position. We sup-
posed that this particular situation could reflect the psy-
chosocial and/or physical stress of the disabled children.
The present results also suggest that the physiological
conditions of patients who remain in a fixed position for
a long period, who are considered to be in a similar con-
dition to paralytic children/patients, can be evaluated by
measuring their sAA levels.
On the basis of our results, we would like to use our
method in clinical practice in future.
5. Conclusion
Salivary alpha-amylase is a useful parameter for evalu-
ating psychophysiological stress in children with dis-
abilities, since it is easy to measure. Thus, the changes in
the sAA levels observed in the present study may reflect
the level of mental stress experienced. Children with
severe and intellectual disabilities can not fully express
their emotions or communicate with their caregivers.
This measurement method is useful for evaluating the
stress levels of such patients.
6. Acknowledgments
The authors would like to thank the university students
of Shimane University Faculty of Education for their
support.

T. INAGAKI ET AL.
15
7. Conflicts of interest
The authors state that there are no conflicts of interests
that relate to this research.
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