Shishido et al. Journal of Physiological Anthropology
https://doi.org/10.1186/s40101-020-00245-7(2020) 39:35

ORIGINAL ARTICLE

Open Access

Effect on autonomic nervous activity ofapplying hot towels for 10 s to the backduring bed baths
Inaho Shishido1, Issei Konya1 and Rika Yano2*

Abstract
Background: Bed baths are a daily nursing activity to maintain patients’ hygiene. Those may provide not only
comfort but also relaxation. Notably, applying a hot towel to the skin for 10 s (AHT10s) during bed baths helped toreduce the risk of skin tears and provided comfort and warmth in previous studies. However, it is still unclear
whether autonomic nervous system is affected by bed baths. Thus, this study investigated the effect on theautonomic nervous activity of applying hot towels for 10 s to the back during bed baths.
Methods: This crossover study had 50 participants (25 men and women each; average age 22.2 ± 1.6 years;
average body mass index 21.4 ± 2.2 kg/m2) who took bed baths with and without (control condition: CON) AHT10s
on their back. Skin temperature, heart rate variability (HRV), and blood pressure (BP) were measured. Subjective
evaluations and the State-Trait Anxiety Inventory in Japanese were also performed.
Results: A significant interaction of time and bed bath type on skin surface temperature was observed (p < .001).
Regarding the means of skin surface temperature at each measurement time point, those for AHT10s weresignificantly higher than those for CON. Although the total state-anxiety score significantly decreased in both the
bed bath types after intervention, the mean values of comfort and warmth were higher for bed baths with AHT10s
than for CON (p < .05) during bed baths; AHT10s was significantly higher in warmth than CON after 15 min (p =.032). The interaction and main effects of time on HRV and BP and that of bed bath type were not significant.
Conclusion: Bed baths that involved AHT10s caused participants to maintain a higher skin temperature andwarmer feeling than under the wiping-only condition; they also provided comfort during the interventions.
However, the bed baths with AHT10s did not allow participants to reach a relaxed state; moreover, there was nochange in autonomic nerve activity. This may be due to participants’ increased anxiety from skin exposure and theintervention being limited to one part of the body.
Keywords: Bed bath, Comfort care, Skin temperature, Autonomic nervous system, Relaxation* Correspondence: r-yano@med.hokudai.ac.jp
2
Faculty of Health Sciences, Hokkaido University, Hokkaido, Japan
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Shishido et al. Journal of Physiological Anthropology(2020) 39:35

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Background
Skin health and integrity are essential in many ways formaintaining health [1]. Personal hygiene assistance, including bed baths, is one of many elements that contribute tomaintaining skin integrity [2]. Therefore, bed bath is key
nursing activity to maintain hygiene and to provide comfort
for bedridden patients who are unable to perform self-caredue to chronic or acute illness [3, 4]. Furthermore, the quality and efficiency of bed baths can have large impact on
quality of life, health, and health care [5, 6].
A literature review found that disposable bed baths
without soap and water performed significantly better
than the bed bath with soap and water in terms of skin hydration [7], skin abnormalities [6], and nurse satisfaction[8, 9] which were studied. On the other hand, it wasreported that there was no difference in the number ofbacteria [10–13], cost, or severe skin lesions [6] dependingon the bed baths method. Regarding the time required forthe bed baths, some studies report that disposable bed
bath was shorter than bed bath with soap and water [9,14], but others report that they were comparable [8]. Although evidences of bed baths are being constructed as
mentioned above, in recent years, insufficient attention topatient satisfaction has been pointed out [3], despite theincreasing focus on patient-centered care [15]. In fact, theevidence of the psychological reactions of the subjects waspoor. It has reported that patients often feel uncomfortable and anxious during the bed baths with soap andwater [12, 16, 17], and even with disposable bed baths
without water and soap, some elderly patients still feel uncomfortable [6] and complain about improper cleaning
duration and poor cleaning [14] Unfortunately, an interview survey to explore the bedridden patients’ experience
with bed baths reported that the patients were not always
asked their bed baths preferences and they believed thatbath methods should be selected by care giver [4]. Suiting
patients’ needs and preferences is patient-centered care,which is argued to contribute to patient satisfaction [15].
Therefore, Cowdell et al. [2] reported that future studies
should include patient-reported outcomes, such as comfort and acceptability.
In Japan, nurses have reported that patients often find theapplication of hot towels to be “a warming and comfortable
experience,” which is why, despite the lack of evidence, theyroutinely apply a hot towel during bed baths before wiping
the patients’ skin. Shishido et al. [18] aimed to decide theoptimal time of hot towel application. They found that 10 s
was the ideal duration from increase of skin temperatureand the height of subjective comfort during interventions.
The bed baths that applied a hot towel for 10 s (AHT10s)
increased skin temperature (+ 0.5 °C) and provided warmthand comfort. Furthermore, Shishido and Yano [19] performed bed baths with AHT10s to the forearms of elderly
people. Although the stratum corneum water content

increased, there was no change the transepidermal water
loss after the bed baths following the AHT10s. These results indicated that the bed baths with AHT10s did not
damage the skin’s barrier function. The bed baths with
AHT10s also elicited comments such as “very pleasant”
and “it is like taking a bath” [19, 20]. As elderly people exhibited a strong positive reaction in spite of the bed bathbeing restricted only to the forearm, we predicted that applying hot towels during bed baths even for a short 10-s
duration could potentially cause relaxation.
Interventions with relaxation effects, such as footbaths
and massages, reduce patients’ anxiety, stress, and pain;
therefore, they are regarded as an important form of carefor enhancing well-being [21–24]. Similarly, interventions like bed baths with AHT10s, which provide thermal stimulation, could be a source of comfort toparticipants [24, 25]. From these results, it can be concluded that comfort and relaxation are related. A reduction in heart rate (HR) by itself considered a sign ofrelaxation, caused either by an increase in parasympathetic nervous system (PNS) activity or a decrease insympathetic nervous system (SNS) activity [26]. Generally, a high-frequency (HF) component is a marker for
pure cardiac PNS activity, while the low-frequency/highfrequency (LF/HF) ratio reflects SNS activity [27]. In thisregard, massages lower LF/HF ratio [28, 29] and increase
HF [30]. Furthermore, footbaths also reduce LF/HF [24].
In addition, thermal stimulus is received on the skin surface and is transmitted to the spinal cord, medulla oblongata, midbrain, and cerebral cortex. It activates the activitiesof the insular cortex and amygdala, areas related to emotion
processing [31], while also affecting the autonomic nervous
system (ANS) and the prefrontal cortex. Therefore, bedbaths with AHT10s providing warmth and comfort might
affect the ANS, and might also induce a relaxation effect.
However, no previous studies have verified this.
We considered that the back was the most effective
site for AHT10s. The percentage of calcitonin generelated peptide positive neurons, which have a sensoryrole, among total neurons projecting to the trapezius
muscle was high [32]. Additionally, the large stimulus
area may help contribute to creating a feeling of warmth[33]. In this study, therefore, it was considered that theeffect by the thermal stimulation was strong on the backfrom the anatomical features, and we selected the backto apply position. Therefore, this study aimed to examine the effect on the autonomic nervous activity of applying hot towels for 10 s to the back during bed baths.
We hypothesized that bed baths with AHT10s would decrease the LF/HF ratio and increase HF. We anticipatedthat performing the bed baths with AHT10s on subjects
with a high level of stress, anxiety, or tension could
maintain skin cleanliness, while also providing relaxation
and alleviating these conditions.

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

Methods
Study design

The study was conducted between December 2019 andFebruary 2020. The study used a crossover design. As aresult, each of the participants received two different
types of bed baths: (1) bed baths that incorporated applying hot towels for 10 s on the back before the skin
was wiped (bed baths with AHT10s), and (2) bed baths
that that incorporated applying dry towels for 10 s (control condition: CON). Half of the participants received
the bed bath with AHT10s the first day, and another halfwith CON the first day. On day 2, the type of bed bath
was switched each group. They were randomly allocatedto a group in which the first type of bed bath preceded
the second type and vice versa for the other group, taking into account the counterbalance.
ParticipantsParticipants included 50 healthy volunteers (> 20 years
old) with no experience or knowledge of bed baths. Eligible participants were recruited from a national university via posters and flyers and all individuals agreed toparticipate in the study. They consisted of 25 men(50.0%) and 25 women (50.0%) and had a mean age of
22.2 ± 1.6 (Table 1). In each experiment, participants
were encouraged to get enough sleep on the night before
the experiment, and to lay off alcohol 8 h before the experiment. On the day of the experiment, participants
were asked to refrain from eating spicy food or drinking
large quantities of caffeinated beverages, performing
strenuous exercises that might cause sweating, and eating at least 1 h before the experiment. The sample size
was calculated using G*Power software (ver. 3.1.9) [34].
There was no prior literature that measured heart ratevariability (HRV) during bed baths. Therefore, the sample size was calculated using the effect size of previous
studies that measured HRV in other nursing care [28,Page 3 of 1030] and similar interventions [18]. As a result, the one
with the largest number of samples was used. Forty-fiveparticipants were calculated as the minimum sample sizewith the following settings: paired t test analysis, .05;
power of test, .80; effect size, .43 [18]. Furthermore, considering the possibility of a 10% of the dropout rate, 50
participants were targeted.
Experiment procedure

The trials occurred within a 6-h window (10:00–16:00)
when the ANS is considered stable [35]. Subjects received
the two types of bed baths at the same time on anotherday. The experiment was conducted in a soundproof room
which reduced noise to 35 dB, to block outside noise andartifacts. The temperature (24–26 °C) and humidity (40–60%) were controlled in this room. Based on the JapaneseIndustrial Standards Committee [36], which requires theillumination within a hospital room be at least 100 lx, theillumination was controlled to a value between 185 and215 lx. The same researcher applied the hot towels andwiped the skin for each participant. Significant differenceswere not between conditions in the experimental environments during the bed baths (Table 1).
Intervention

In order to reduce the initial effect, subjects watched avideo of the bed bath being performed before the experiment. Participants changed the hospital gown and werethen placed in a sitting position, leaning forward tolightly hug a pillow placed on table.
Bed baths with AHT10s

The time of the hot towel application was 10 s in thisstudy. This is because in a previous study [18], the evaluation of comfort was found to be the highest when a hot
towel was applied for 10 s, with some people complainingof coldness or discomfort when the towel was applied forTable 1 Subjective characteristics and implementation environment (n = 50)
Mean (SD)Bed bath with AHT10s

CON

95% CI for
the differenceAge (years)

22.2 (1.6)–

Body mass index (kg/m2)

21.4 (2.2)–

Muscle mass (kg)43.4 (8.0)–

Body fat percentage (%)

21.4 (8.1)–

2

t value

P value–

Area of back (cm )1641.1 (253.3)

Time required for bed bath84.0 (4.0)

84.7 (3.9)− 1.5–0.3− 1.37.176

Room temperature (°C)

25.7 (0.4)

25.6 (0.4)− 1.4–1.0− 0.34.738

Humidity (%)

35.1 (3.3)

34.7 (3.4)− 0.1–0.1

0.48

.634

Implementation environment

Paired t test. The area of the back was calculated by measuring the length (transverse boundary line: both axillary lines, upper boundary line: line connecting bothacromion, lower boundary line: line connecting both iliac crests). AHT10s applying hot towels for 10 s to the skin, CI confidence interval, CON the bed bath with
applying dry towel to the skin, SD standard deviation

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

15 s or more. The protocol of the bed bathing methods isshown below. Two cotton hand towels (74 × 35 cm, 82.0
± 2.0 g) were placed in a thermostatically controlled bath(TR-2AR Thermal Robo; As One, Osaka, Japan) filled withwater at a temperature of 50 ± 0.02 °C. After heating, excess water was wrung out of the towels, leaving them withthe final weight of 480.0 ± 5.0 g. The hot towels folded in
two were immediately applied to participants’ back, withthe upper edge of the towels placed along a line connecting the right and left acromion. The researcher’s hands
were placed on the hot towels, carefully applying constantpressure from the center of the towel; held in that statefor 10 s (AHT10s) (Fig. 1). After removing the hot towels,
the left and right backs were wiped three times each in a
direction parallel to the spinal column (Fig. 2(A1–A3 andB1–B3)) with another hot towel (final weight of 240.0 ±5.0 g). Furthermore, using the same hot towel, the left andright flanks were wiped four times in a direction perpendicular to the spinal column (C1–C4 and D1–D4). Then,the skin was wiped with a dry towel. The pressure for applying and wiping was 23–25 mmHg [37]. The hot towel
surface was replaced with an unused surface every time
one part was wiped. After completion of the bed bath, thesubject was made to wear clothes immediately.

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Fig. 2 Experimental setup. Reference line, a line connecting theright and left acromion. * The skin temperature of the back wasmeasured attaching a probe. Wiping was performed in the directionof the arrow in the time series shown

Bed baths with applying dry towels (CON)The dry hand towels, which were not heated were foldedin two and immediately applied to participants’ back, withthe upper edge of the towels placed along a line connecting the right and left acromion. The researcher’s hands
were placed on the hot towels, carefully applying constantpressure from the center of the towels; held in that statefor 10 s. After removal of the dry towels, wiping was performed in the same method as the baths with AHT10s.
Data collection

The total time for this trial was approximately 32 min.
Data were collected 5 min before intervention (T1), at
the beginning of the experiment (T2), immediately after
applying the hot towels to the skin (T3), immediately
after wiping the skin (T4), immediately after wiping theskin with the dry towel (T5), 1–5 min after T5 (T6–10),
10 min after T5 (T11), and 15 min after T5 (T12) (Fig.
3). “Pre” was defined as the period between T1 and T2,
and “Post” between T6 and T10.
Physiological measurements
Heart rate variability
Fig. 1 Application of the hot towels to the back. The hot towels applied
to participants’ back, with the upper edge of the towels along placed aline connecting the right and left acromion. The researcher’s hands wereplaced on the hot towel, carefully applying constant pressure from thecenter of the towel

An electrocardiogram (ECG) was performed with electrodes (Vitrode F-150M; Nihon kohden, Tokyo, Japan) attached to the chest. The ECG data was monitored by using
a data logger (Biolog, DL-2000; S&ME Inc, Tokyo, Japan),
HRV sensor (DL-310; S&ME Inc). All participants wereasked to sit comfortably on a bed for 10 min before theShishido et al. Journal of Physiological Anthropology(2020) 39:35

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Fig. 3 The experimental protocol. BP blood pressure, HR heart rate, HRV heart rate variability. T1, 5 min before intervention: T2, the beginning of theexperiment: T3, immediately after applying the hot or dry towel to the skin: T4, immediately after wiping the skin: T5, immediately after wiping the skinwith the dry towel: T6–10, 1–5 min after T5: T11, 10 min after T5: T12, 15 min after T5. Pre, between T1 and T2: Post, between T5 and T10

recording of any ECG data. Baseline data were recorded for
5 min followed by intervention. During the intervention
period, all subjects remained seated on the same bed thatthey were on before ECG data was being recorded. Afterthe intervention period, all subjects remained seated while
ECG data was recorded for 5 min. The HR and beat-tobeat detection (R-R interval) were gained using R-wave of
the ECG. An HF component (0.15–0.40 Hz) and an LF
component (0.04–0.15 Hz) of the power spectrum of R-R
interval variability was determined by using the maximum
entropy method (Memcalc/TARAWA; SUWA Trust,Tokyo, Japan). These values were used to determine the 5min averages for HF component (ms2) reflecting the PNS
activity for and LF/HF ratio reflecting the SNS activity [27].
Blood pressure

Blood pressure (BP) was measured with an electronic
sphygmomanometer (ES-H56; Terumo, Tokyo, Japan) at
T1 and T10.
Skin temperature on the back

Only the skin temperature was measured in this study because the bed baths were for a short duration (80 to 90 s),
the thermal stimulus was small, and the possibility of changing the core temperature was low. The skin temperatureof the back was measured by attaching a probe (Hardware
N543; Nikkiso-Therm, Tokyo, Japan; accuracy, ± 0.1 °C)
every second starting from before bed bath (T1) to 15 minafter dry wiping (T11), and the value at which data was
extracted at each time point was taken as the measured
value (Fig. 3). We attached the probe at only a single location on the back: (1) to confirm whether an increase in skintemperature could be observed, as in previous research[18, 19]; (2) because the attached probe interferes with wiping; and (3) because the heat of the hot towel is not directly
conducted to the skin by attaching probes at multiple
locations.
Psychological measurements
State-Trait Anxiety Inventory-JYZThe State-Trait Anxiety Inventory-JYZ (STAI-JYZ) instrument was used to assess self-reported anxiety levels. The
STAI-JYZ translated STAI-Y [38] into Japanese to reflect
the cultural background of Japan and traits of Japanesepeople [39]. It can measure both “trait-anxiety” and “stateanxiety”. Trait-anxiety shows a tendency for an individual
perception or response to a threatening situation, andstate-anxiety shows transient response to an anxietyprovoking event. Participants answered questions aboutstate-anxiety before and after the bed baths, and questions
about trait-anxiety only before the bed baths. The inventory consisted of 20 trait and 20 state-anxiety items andwere summed for a total score ranging from 20 to 80, withscores based on a four-point Likert scale (1, Not at all; 2,Somewhat; 3, Moderately so; 4, Very much so), withhigher scores reflecting higher levels of anxiety. Hidano
et al. [39] provided reference values for STAI-JYZ measurements (High anxiety: 55–80; Low anxiety: 20–44).
Subjective evaluation

Questionnaires were administered to participants following
each bed bath type at T10 and T12. At T10, the subject
confirmed the sensation during bed bathing. Each participant rated comfort, warmth, ability to remove dirt, andsleepiness on a five-point Likert scale (1, Not at all; 2, Not
so much; 3, Neither; 4, Somewhat so; 5, Very much so). At

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

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T12, 15 min after the end of wiping, each participant thenrated the comfort, warmth, and sleepiness on the same
five-point Likert scale.

protected. All participants provided informed consent.
If a participant grumbled of excessive heat or pain,
the experiment was immediately stopped and the skincooled. This study was approved by the Ethical Review Board of the authors’ affiliated university (approval no.19-68) and was performed in accordancewith the Declaration of Helsinki.

Data analysis

HRV, BP, skin temperature, and state-anxiety were analyzed using mixed-linear model for two-way repeatedmeasures ANOVA, and a Bonferroni correction was carried out to adjust for multiplicity. In the mixed-linear
ANOVA model, time and types were defined as a fixedfactor, while subjects were defined as a random factor.
The factors in this ANOVA were “time” (pre and postor T2–T12) and “bed bath type” (bed bath with AHT10s
or CON). For the interaction, “time and bed bath type”
was set up. If at least one of the factors or interactions
was significant, single-factor repeated-measures ANOVA
and multiple comparison tests were performed on themeans. Paired t tests were also performed on the means
to compare data between treatment types. Analyses wereconducted using SPSS version 26 statistical software(IBM, Armonk, New York, NY, USA).

Results
HRV

Forty-three subjects (22 men and 21 women), excluding
seven subjects whose HRV values were more than 1.5
times the 1st and 3rd quartiles of the interquartile range,
were analyzed. Nunan et al. [40] found that the mean of
the HF component was 657 ± 777 ms2 and that of LF/
HF ratio was 2.8 ± 2.6 in healthy adults. The main effects of time on HF component and LF/HF ratio, andthat of bed bath type were not significant (Table 2). Theinteractions did not show any significance.

Ethical considerations

HR, systolic blood pressure, and diastolic blood pressure

People interested in participating were given verbal andwritten explanations about the following points: the study
objective, experimental methods, the right to dropout at
any time, and assurance that anonymity would be

HR, systolic blood pressure (SBP), and diastolic bloodpressure (DBP) values did not show a significant main
effect for time and bed bath type. The interactions were
not significant (Table 2).

Table 2 Comparison of bed baths with AHT10s and CON: HRV, HR, BP (n = 43)
Bed bath with AHT10s

CON

Main effect
TypeInteraction
type х time

Time

Pre

Post

Pre

Post

F (df)P

F (df)P

F (df)P

Mean (SD)567.3 (326.6)

569.3 (345.7)

536.7 (361.7)

600.8 (459.8)< 0.01 (1,126).990

0.87 (1,126).353

0.77 (1,126).383

95% CI462.9–675.7

462.9–675.7

425.4–648.0

459.3–742.3

1.38 (1,126).243

3.33 (1,126).070

1.91 (1,126).170

1.05 (1, 126).308

0.51 (1, 126).475

0.07 (1, 126).785

0.56 (1, 126).457

< 0.01 (1, 126).968

0.93 (1, 126).337

1.23 (1, 126).271

0.83 (1, 126).365

0.14 (1, 126)

.705

2

HF (ms )LF/HF
Mean (SD)

1.9 (1.5)

2.6 (2.3)

2.5 (1.8)

2.5 (1.9)

95% CI

1.5–2.4

1.9–3.3

1.9–3.0

2.0–3.1

Mean (SD)68.9 (10.5)

68.3 (8.8)

68.3 (9.8)

68.0 (10.4)

95% CI

65.7–72.1

65.6–71.0

65.3–71.3

64.8–71.2

HR (bpm)

SBP (mmHg)
Mean (SD)106.4 (9.6)

107.4 (10.3)

106.7 (10.3)

105.6 (11.5)

95% CI

103.5–109.4

104.3–110.6

103.5–109.9

102.0–109.1

Mean (SD)63.7 (7.1)

62.9 (7.8)

64.0 (8.0)

63.8 (7.4)

95% CI

61.5–65.8

60.5–65.3

61.6–66.5

61.6–66.1

DBP (mmHg)

A mixed-linear model for two-way repeated-measures ANOVA, and a Bonferroni correction. AHT10s applying hot towels for 10 s to the skin, BP blood pressure, CI
confidence interval, CON the bed bath with applying dry towel to the skin, DBP diastolic blood pressure, LF low frequency component (0.04–0.15 Hz), HF highfrequency component (0.15–0.40 Hz), HR heart rate, HRV heart rate variability, SD standard deviation, SBP systolic blood pressure. Pre, between T1 (5 min before
intervention) and T2 (the beginning of the experiment): Post, between T6 (immediately after wiping the skin with the dry towel) and T10 (5 min after wiping theskin with the dry towel)

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

Skin temperature on the backThe mean skin temperature on the back at T2 was 34.7 ±
0.8 (bed baths with AHT10s) or 34.7 ± 0.7 °C (CON).
There were significant main effects of time on skintemperature [F (10,1029) = 257.64, p < .001] and bed bathtype [F (1,1029) = 815.27, p < .001]. A significant interaction of time and bed bath type was observed [F (10,1029)= 219.90, p < .001] (Fig. 4). For the mean at each measurement point, those for AHT10s were significantly higher
than those for CON at T3 to T12 (p < .01). The mean skintemperature was significantly higher at T3 (3.4 ± 0.8 °C, p <.001), T11 (0.2 ± 0.4 °C, p = .002), and T12 (0.2 ± 0.4 °C, p= .016) relative to T2 for bed baths involving AHT10s.
However, the mean skin temperature at T3 to T10 was significantly lower than at T2 (p < .05) for CON.
STAI-JYZThe score of trait-anxiety for the subjects in this study
was slightly lower but still similar to the average value forhealthy adults [39]. Although there was a significant main
effect of time on state-anxiety, was not of bed bath type(Table 3). The mean of state-anxiety score of both types of
bed bath decreased significantly at T10 (p < .001). There
were no significant differences between the two types of
bed baths in trait-anxiety before the experiment.
Subjective evaluation

The mean values for comfort and warmth at T10 of bed
baths with AHT10s were significantly higher than thosePage 7 of 10

of CON (p < .05) (Table 4). At T12, AHT10s was significantly higher in warmth than CON (p = .032).

Discussion
In this study, we investigated whether the warmth andcomfort of bed baths using the hot towels application to
the back affected ANS in 50 healthy adults. Our results
showed that, following a bed bath with AHT10s on theback, skin temperature increased (+ 3.4 °C), as in a previous
study [18], and was significantly higher than that of CON
until 15 min after bed baths. In addition, bed baths with
AHT10s provided warmth until 15 min after bed baths,
and both warmth and comfort were significantly higher forthe bed baths with AHT10s than for CON at 5 min after
the end of dry wiping. However, HRV, which is an index of
ANS, and HR and BP, which are related indicators, did notchange after the bed baths, and there was no significant difference between the bed baths with AHT10s and CON
conditions. These results suggested that short-term warmthand comfort did not necessarily lead to a relaxation effect.
This result has a similarity that is found by a previous research [41] in which a 10-min warm hand bath was administered; the results of subjective evaluation and HRV
suggested that the intervention increased subjective warmthand comfort without affecting ANS.
There may be two reasons why AHT10s did not affect
ANS. First, the intervention was limited to one part ofthe body. For stimulus reception and emotion, cutaneous C-tactile afferents send a signal to areas of the brain
involved with positive emotions [42]. In other words, theFig. 4 Time courses of skin temperature of healthy adults (n = 50). † Paired t test. †††p < .001, ††p < .01. * Mixed-linear model for two-way
repeated-measures ANOVA, and a Bonferroni correction. ***p < .001, **p < .01, *p < .05. AHT10s, applying hot towels for 10 s to the skin: CON,the bed bath with applying dry towel to the skin. T2, the beginning of the experiment: T3, immediately after applying the hot or dry towel to theskin: T4, immediately after wiping the skin: T5, immediately after wiping the skin with the dry towel: T6–10, 1–5 min after T5: T11, 10 min after T5:
T12, 15 min after T5

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

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Table 3 Comparison of bed baths with AHT10s and CON: STAI (n = 50)
Bed bath with AHT10s

CON

Type
State-anxiety

InteractionType хTimeMain effectTime

Mean (SD)

95% CI

Mean (SD)

95% CIF (df)P

F (df)P

F (df)

PPre

36.3 (7.6)

34.1–38.5

35.7 (6.5)

33.9–37.6

0.02 (1, 147)

.853

51.54 (1, 147)<.001

1.08 (1, 147)

.301

Post

32.2 (6.3)***30.4–34.0

32.7 (5.7)***

31.1–34.3

45.4 (10.0)

42.6–48.3

44.8 (9.9)

42.0–47.6

–

–

–

–

–

–

Trait-anxiety

A mixed-linear model for two-way repeated-measures ANOVA, and a Bonferroni correction. ***p < .001. AHT10s applying hot towels for 10 s to the skin, CI
confidence interval, CON the bed bath with applying dry towel to the skin, SD standard deviation. Pre, between T1 (5 min before intervention) and T2 (thebeginning of the experiment): Post, between T6 (immediately after wiping the skin with the dry towel) and T10 (5 min after wiping the skin with the dry towel)

stimulation of C-tactile afferents could be related to
the feeling of comfort, and continuous warm stimulation of skin with C-tactile afferents might lead to acontinued sense of comfort. This suggests that in
Kudo and Sasaki’s [41] study and our study, because
the intervention was applied to only one part of thebody, the skin stimulation was not strong enough to
influence ANS, resulting in no relaxation effect. However, we did not examine whole-body effects to avoid
influencing HRV from changes in posture and theburden associated with prolonged rest. Thus, the relaxation effect and the maintenance of comfort andwarmth due to AHT10s to the whole body should beverified in future studies.
The second reason relates to the possibility of increased anxiety associated with skin exposure. Although
bed baths constitute a fundamental form of care inmaintaining patients’ skin hygiene, they could expose
patients’ skin to others and be considered an invasion ofprivacy [17]. It has been reported that a lack of thisawareness among professionals causes anxiety in patients, and their anxiety during bed baths was stronger
than that during shower baths [16]. The mean of thestate-anxiety score for both types of bed baths decreased
significantly in this study; however, it may have beendifficult for subjects to fully relax during the bed baths
because of exposed skin.

Contrary to the hypothesis, the LF/HF ratio for bed baths
with AHT10s tended to increase after bed bathing, although there was no significant difference between the before and after values, and thermal stimulation might haveactivated the SNS. In addition to increasing subjective comfort, thermal stimulation activates brain areas such as theorbitofrontal, medial prefrontal, and cingulate cortices [43,44]. The orbitofrontal cortex and medial prefrontal cortex
are primarily behavior-related [45] and play an importantrole in intrinsic motivation, such as working hard for yourown benefit [46]. Furthermore, Kolcaba [47] reported thatwhen comfort is enhanced, individuals are motivated to engage in health-seeking behaviors, with an ultimate improvement in outcome. Based on these results, future studies
should evaluate the effect of bed baths while applying hot
towels on the back from multiple aspects, such as the
cognitive-behavioral aspect, and by mapping brain activity
rather than assessing the effect only on the ANS.

Conclusions
Since the heat from the hot towel was transferred to theskin, the bed baths that involved AHT10s caused participants to maintain a higher skin temperature and warmer
feeling than under the wiping-only condition and also
provided comfort during the intervention. Though an effect on the ANS from brain region activity (for example,
activity in the hypothalamus from thermal stimulation)

Table 4 Comparison of bed baths with AHT10s and CON: Subjective evaluation (n = 50)
Mean (SD)

95% CI for
the differencet value

P value

Bed bath with AHT10s

CON

Comfort

4.6 (0.6)

4.4 (0.7)

0.0–0.4

2.48

.017

Warmth4.8 (0.4)

4.2 (0.9)

0.3–0.8

4.60< .0015 min after dry wiping (T10)

Ability to remove dirt

3.9 (0.8)

3.7 (0.8)− 0.0–0.4

1.70

.095

Sleepiness3.3 (1.2)

3.4 (1.1)− 0.5–0.3− 0.57.569

4.1 (0.6)

3.9 (0.8)− 0.0–0.4

1.59

.118

15 min after dry wiping (T12)
ComfortWarmth3.6 (0.9)

3.3 (1.0)

0.4–1.0

2.64

.011

Sleepiness3.8 (1.1)

3.7 (1.0)

0.1–1.1

0.39

.700

Paired t test. AHT10s applying hot towels for 10 s to the skin, CI confidence interval, CON the bed bath with applying dry towel to the skin, SD standard deviation

Shishido et al. Journal of Physiological Anthropology(2020) 39:35

has been reported in preceding research, the bed baths
with AHT10s did not affect the ANS; therefore, a relaxation effect might not have been achieved, even if
warmth and comfort were obtained. This may be due toparticipants’ increased anxiety from skin exposure andthat the intervention was limited to one part of the body.
Further, the results of previous studies on the effects ofnursing care on brain region activity and comfort in response to stimulation indicate that the LF/HF ratio
tended to increase for the bed baths with AHT10s.
Therefore, it is expected that comfort will impact a person’s cognitive behavior, so it is necessary to further verify the effect of bed baths with AHT10s.
Abbreviations
AHT10s: Applying hot towels for 10 s to the skin; ANS: Autonomic nervous
system; BP: Blood pressure; CON: Bed baths with applying dry towels for 10 sto the skin; DBP: Diastolic blood pressure; ECG: Electrocardiogram; LF: Lowfrequency; HF: High-frequency; HR: Heart rate; HRV: Heart rate variability;
PNS: Parasympathetic nervous system; SBP: Systolic blood pressure;SNS: Sympathetic nervous system; STAI: State-Trait Anxiety Inventory
Acknowledgements
The authors would like to thank all those who participated in this study.
Authors’ contributions
IS designed research, collected all data, performed the statistical analysis, andwrote the paper. IK participated in the design of this study and helped toperform the statistical analysis. RY participated in the design of this study
and helped to draft the manuscript. All authors read and approved the final
manuscript.
Authors' information
IS (R.N., M.S.N.) is a PhD student in Graduate School of Health Sciences,
Hokkaido University, Hokkaido, Japan. IK (R.N.) is MSN student in Graduate
School of Health Sciences, Hokkaido University, Hokkaido, Japan. RY (R.N.,
PhD) is a professor in Faculty of Health Sciences, Hokkaido University,
Hokkaido, Japan.
Funding
Not applicable.
Availability of data and materials
The datasets during and/ or analyzed the current study are available fromthe corresponding author on reasonable request.
Ethics approval and consent to participate
The ethics committee at Hokkaido University Faculty of Health Sciences
approved the present study (approval no.19-68). The participants received an
explanation of aims and experimental methods, including the right towithdraw from the study at any point without prejudice and insurance thatanonymity would be protected throughout all components of the study. All
participants provided informed consent before participating in thisexperiment.
Consent for publication
We obtained the consent for publication from our participants by oral
explanation and a document. Informed consent to participate in our study
included this process.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Graduate School of Health Sciences, Hokkaido University, Hokkaido, Japan.
2
Faculty of Health Sciences, Hokkaido University, Hokkaido, Japan.

Page 9 of 10

Received: 18 May 2020 Accepted: 9 November 2020

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