=Paper=
{{Paper
|id=Vol-3276/SSS-22_FinalPaper_140
|storemode=property
|title=A Thermal Environment that Promotes Efficient Napping
|pdfUrl=https://ceur-ws.org/Vol-3276/SSS-22_FinalPaper_140.pdf
|volume=Vol-3276
|authors=Miki Nakai, Tomoyoshi Ashikaga, Takahiro
Ohga, Keiki Takadama
|dblpUrl=https://dblp.org/rec/conf/aaaiss/NakaiAOT22
}}
==A Thermal Environment that Promotes Efficient Napping==
https://ceur-ws.org/Vol-3276/SSS-22_FinalPaper_140.pdf
A Thermal Environment that Promotes
Efficient Napping
Miki Nakai,1 Tomoyoshi Ashikaga,2 Takahiro Ohga,3 Keiki Takadama4
DAIKIN INDUSTRES LTD., 1,2,3 The University of Electro-Communications,4
miki2.nakai@daikin.co.jp,1 tomoyoshi.ashikaga@daikin.co.jp,2 takahiro.Ohga@daikin.co.jp,3
keiki@inf.uec.ac.jp4
Abstract the nap (eliminating drowsiness and improving perfor-
People need to maintain good health to live productive and mance) is not clear. In previous studies about nap, it has
creative lives, and sleep greatly contributes to maintaining been described about optical nap length (Hayashi et al.,
good health. In recent years, some companies have begun al- 1999, 2003, 2004, 2005), light effect (Hayashi et al., 2007),
lowing time for sleep during work hours as “power naps” to sound effect (Toma et al., 2004). However, it is still un-
eliminate drowsiness and improve efficiency. In this article, known about effect of a thermal environment on nap qual-
we report on the optimal thermal environment for efficient ity.
naps during the daytime when the body is active and the ef-
Since the environmental temperature controlled by the air
fect that naps have on improving productivity. This study
uses questionnaires on drowsiness before and after the test conditioner directly affects the body temperature regula-
along with the Psychomotor Vigilance Task (PVT) and N- tion, it is considered to have a great influence on the "sleep
back task to evaluate productivity improvements in test sub- quality" that rests the brain. In addition, air conditioners are
jects when room temperature is changed for each scene of becoming widespread all over the world, and more and
“reclining for nap,” “sleeping,” and “waking from nap.” Test more homes are installing "one air conditioner in one
results show that differences in room temperature can pro- room". Therefore, in this study, we focus on thermal con-
mote the onset of sleep, maintain sleep, and stimulate wake- trol during nap using an air conditioner that can be widely
fulness. By optimally controlling these factors, it is possible applied, and report the results of evaluating the effect of
to take a short high-quality nap to improve productivity. As environmental temperature control on the quality of nap
sleep is said to be related to the function of the autonomic
(eliminating drowsiness and improving performance).
nervous system, it is believed that the thermal environment
exerts influence on the autonomic nervous system and affects
the quality of sleep, even when sleep duration is short.
2. Optimal thermal control for daytime naps
1. Introduction Room temperature inside the nap room is adjusted during
the 30-minute nap according to the three stages of “Reclin-
Recently, the amount of sleep that many people in Japan ing for nap,” “Sleeping,” and “Waking from nap.” And the
obtain each night has declined (NHK Broadcasting Culture environmental temperature at each stage was controlled to
Research Institute, 2020), and more than 70% of Japanese ensure a comfortable and moderate sleep depth. Fig 1 show
men and women 20 years of age and older sleep an average
the example of the thermal control for nap.
of less than 7 hours. Consequently, more than 30% of Jap-
anese people between the ages of 20 and 59 years old suffer (1) Reclining for nap...
from “daytime drowsiness” at least three times a week The warm environment is thought to enhance relaxation
(Ministry of Health, Japan, 2019), leading to a decline in before the nap, which accelerate the onset of sleep.
productivity. So, there is increasing interest in good sleep. (2) Sleeping...
There are the following previous studies on nighttime sleep Assist restful sleep with a Slightly cooler room temperature
and athletic performance (Cheri D Mah et al., 2011). We (3) Waking from nap...
measured the shooting accuracy, evels of daytime sleepi- At higher temperatures, it encourages the body to awaken
ness, and Psychomotor Vigilance Task (PVT) when 10
basketball players slept for 10 hours or more and did not. And Fig.2 show the typical example of sleep depth by this
As a result, when sleeping for 10 hours or more, the shoot- thermal control (W:wake, R:REM sleep, N1: NREM Sleep
ing accuracy was significantly improved and the drowsi-
Stage 1, N2: NREM Sleep Stage 2, N3: NREM Sleep Stage
ness and PVT reaction time were decreased as compared
with the short sleep. 3).
It is said that naps are also effective in relieving drowsi-
ness and improving performance. But the effect of the sur-
rounding environment when taking a nap on the quality of
___________________________________
In T. Kido, K. Takadama (Eds.), Proceedings of the AAAI 2022 Spring Symposium
“How Fair is Fair? Achieving Wellbeing AI”, Stanford University, Palo Alto, California,
USA, March 21–23, 2022. Copyright © 2022 for this paper by its authors. Use permitted
under Creative Commons License Attribution 4.0 International (CC BY 4.0).
88
3.2 Experimental equipment
Test subjects wear an electroencephalograph G (Sleep
Scope, SleepWell Co., Osaka, Japan) (Yoshida et al., 2015)
and EEG during sleep of the subject was measured.And The
room temperature of the nap room was measured using en-
vironmental sensor (2JCIE-BU01, OMRON Co., Kyoto, Ja-
pan).
Fig. 1 the thermal control example for nap
4. Method
4.1 Participants and Protocol
The test subjects are 6 males and 5 females in their twenties,
and the amount of their clothes was kept constant. From Jan-
uary 2020 to February 2022, 143 tests were conducted. The
test subject is given a questionnaire on drowsiness (The
Stanford Sleepiness Scale, Table1), and 2 types of produc-
Fig. 2 the typical example of sleep depth tivity measurement tests (PVT-B; Psychomoter Vigilance
Task, Fig. 4 and N-Back task, Fig. 5) are conducted. PVT-
B objectively assesses fatigue-related changes in alertness
nap associated with sleep loss, extended wakefulness, circa-
dian misalignment, and time on task. In this nap test, the re-
3. Experimental Environment
action speed was measured by clicking a PC mouse in re-
3.1 nap room sponse to a lit signal on the PC monitor in order to evaluate
A nap room of H2315 x W (2400 + 385) x D1200 mm (Fig. awakening degree. N-Back task is used extensively in liter-
3) was created, and a bed was installed in the nap room. Dur- ature as a working memory (WM) paradigm. In this nap test,
ing the test, the entrance sliding door was kept closed, and the test subjects have to memorize details to several ques-
the test was conducted while ensuring sound insulation and tions while answering a simple calculation formula to eval-
light shielding. The humidity inside the experimental nap uate it.
room remains within a range of 40-60%, and a small space After that, a 10-minute rest period is provided before the
multi-cassette air conditioner "cocotas" manufactured by test subject takes a 30-minute nap. After waking, the test
Daikin Industries was installed to control the temperature of subject receives another rest period of 5 minutes and is again
the nap room. given a questionnaire on drowsiness. These productivity
measurement tests are administered twice to the test subject
after waking at 1-hour and 3-hour intervals.
Table 1 The Stanford Sleepiness Scale
Fig. 3 nap room
89
Fig. 4 PVT-B screen
Fig. 6 the thermal control example for nap
(A: the temperature control in a V-shaped
pattern, B:no thermal control)
Table 2 Evaluation items and contents
Fig. 5 N-Back Task screen
4.2 Room temperature conditions
Room temperature inside the nap room is adjusted during
the 30-minute nap according to the three stages of “Reclin- 5. Results
ing for nap,” “Sleeping,” and “Waking from nap” as shown 5.1 (1) Reclining for nap
in Fig.6(A,B). By room temperature, it is measured about Fig. 7 shows the results of sleep onset latency at room
"changes in sleep depth" and evaluated about "productivity temperature before falling asleep. In order to realize a ther-
before and after the nap" as shown in Table2. At the time of mal environment that encourages rapid sleep onset, we hy-
nap, the following two room temperature environments pothesized that by setting the room temperature before fall-
ing asleep to a warmer temperature, the relaxing effect
were applied. would be enhanced and it would be easier to fall asleep.
A: the temperature control in a V-shaped pattern Room temperature before the onset of sleep is set at one of
-It is kept slightly warm room temperatures before sleep three settings: low (25 ℃ or less), neutral (26 ℃), or high
onset, kept lower after sleep onset, and raised before waking. (27℃). The time required before the onset of sleep at each
B: no thermal control temperature environment is evaluated. As expected, A ten-
dency was seen in which sleep onset latency shortened
-It is maintained a neutral temperature from before sleep when the room temperature was kept slightly warm (27℃).
onset to waking up.
90
5.1 (3) Waking from nap
Contrary to the sleeping con-
ditions during sleep, we hy-
pothesized that "a high room
temperature has the effect of
promoting awakening" and
verified that raising the room
temperature immediately be-
fore waking up promotes
awakening with less drowsi-
ness. We compared the differ-
ence in sleep depth between
the case where the room tem- Fig. 9 Sleep depth percent-
perature was not changed dur- age (%) and room tempera-
Fig. 7 Sleep onset latency (minutes) and room temper- ing sleep and the case where ture (° C) before waking
ature (℃) before sleep onset the room temperature was
raised to 27 ° C or higher 3 minutes before the wake-up time.
5.1 (2) Sleeping As a result, as shown in Fig. 9, when the room temperature
Daytime naps are said to be "optimal for NREM Sleep 3 minutes before waking up was 27 ° C or higher, the sleep
Stage 2 (N2)", which does not increase sleep inertia after depth tended to be shallower.
waking up (Stampi C. et al., 1990). Therefore, with the aim
of realizing a "thermal environment that can maintain N2"
during sleep, the hypothesis that "a slightly cooler tempera- 5.1 Result: Thermal control method obtained from the
ture is comfortable and does not interfere with sleep", that demonstration result
is, "a thermal environment that can maintain sleep". The ex- From the results of 5.1(1), (2) and (3), the thermal control
periment was conducted. It was confirmed that test subjects method shown in Fig. 10 is considered to be optimal for ef-
reached and maintained N2 10 minutes after the onset of ficient short-time sleep during the day.
sleep at a room temperature of 26℃, compared to no change
in room temperature (Fig.8 (A)-1, (B)-1). Fig. 8 (A) -2 and
(B) -2 show examples of sleep depth when the test was per-
formed with control A or B.
Fig. 10 optimal thermal control
5.2 Performance improvement effect with or without
thermal control
This time, we also verified the effect of the application of
thermal control on the performance after waking up. As for
the verification method, three items of "reaction speed,
working memory, and drowsiness" were compared 1 hour
after waking up and 3 hours after waking up. As a result, in
Fig. 8 Sleep depth percentage (%) and elapsed time from about 50 cases tested with thermal control, which provides
sleep (in minutes) (A-1: control A, B-1: control B) the best sleep condition, performance was improved com-
Sleep depth and elapsed time from sleep (in minutes) pared to the case without thermal control. The results are
(A-2: control A, B-2: Control B)
shown in the Table 3.
91
Table 3 Improvement in reaction speed, working 6.2 Circadian rhythm
memory, and drowsiness by thermal control compared Under the influence of circadian rhythm, it is generally said
to cases without thermal control that it is hard to feel sleepy in the morning and it feels sleepy
in the afternoon (Lavie, P et al., 1985).
6. Discussions
We introduced a thermal control that allows you to take a
nap comfortably and effectively even during the daytime
when your arousal level is high. In addition, taking a 30- Fig. 11 Sleep onset la- Fig. 12 Sleep onset la-
minute nap during the day using this technology has the ef- tency (minutes) for men tency (minutes) for men
fect of reducing drowsiness after waking up and improving and women at room tem- and women at room
reaction speed and working memory compared to taking a perature of 25° C temperature of 27 ° C
nap without thermal control.
In future efforts, we would like to consider customizing the
thermal control in consideration of the following two points. Fig.13 shows an example of general sleep depth when tak-
1). Gender difference ing a nap in the morning and taking a nap in the afternoon.
2). Circadian rhythm As these figures show, drowsiness is less likely to be felt in
In fact, the results of this experiment also show the effects the morning, resulting in lighter sleep and increased awak-
of 1). gender differences and 2). circadian rhythms, and we ening. On the other hand, since it is easy to feel drowsiness
believe that more precise evaluation of these results will en- in the afternoon, the depth of sleep tends to become deeper
able the realization of individual thermal control methods. as time passes after sleep onset.
Therefore, by applying the result of 5.1(3), in the case of a
nap in the morning, we will consider maintaining the room
6.1 Gender difference temperature while sleeping without raising it before waking
Regarding 5.1 (1), we received multiple answers such as up in order to obtain sufficient N2 time. In the case of a nap
"it was cold" and "it was hot" in the questionnaire after in the afternoon, we will consider raising the room temper-
taking a nap, so we examined how to feel the temperature ature before waking up in order to avoid reaching N3.
between men and women. We compared sleep onset latency
by gender for the lower room temperature of 25°C. As a re-
sult, as shown in Fig.11, no significant difference was ob- (a) (b)
served between men and women. However, 43% of women
Sleep depth
(3 out of 7 cases) and 23% of men (3 out of 13 cases) an-
swered that they were "cold" by the time they fell asleep.
Therefore, it was considered that women tended to feel
colder. elapsed time from sleep (in minutes)
On the other hand, when the room temperature was slightly
warmer at 27 ° C, a significant difference was found when Fig. 13 Sleep depth and elapsed time from sleep (in
comparing sleep onset latency by gender (Fig. 12, p <0.05). minutes) (a: in the morning, b: in the afternoon)
Furthermore, 2.3% of women (1 out of 43 cases) and 5.1%
of men (4 out of 78 cases) answered that they were "hot" by
the time they fell asleep. Therefore, it was suggested that
men may tend to feel hotter.
7. Conclusion
Thermal control was introduced that enables comfortable
and efficient naps even during the day when the degree of
alertness is elevated. Additionally, when a 30-minute nap is
taken during the day with heat control using this technology,
92
compared to no use of heat control, drowsiness decreases Yoshida, M.; Kashiwagi, K.; Kadotani, H.; Yamamoto, K.;
while reaction speed and working memory improve. Koike, S.; Matsuo, M.; Yamada, N.; Okawa, M.; and Urade,
Y. Validation of a portable single-channel EEG monitoring
system. 2015. Journal of Oral Sleep Medicine, 1, 140–147.
References
Cheri, D.; Kenneth, E.; Eric, J.; and William, C.; 2011. The
effects of sleep extension on the athletic performance of col-
legiate basketball players. Sleep, 34(7):943-50
Hayashi, M.; Watanabe, M.; and Hori, T.; 1999. The effects
of a 20-min nap in the mid-afternoon on mood, performance
and EEG activity. Clinical Neurophysiology, 110, 272-279.
Hayashi, M.; Fukushima, H.; and Hori, T.; 2003. The effects
of short daytime naps for five consecutive days. Sleep Re-
search Online, 5, 13-17.
Hayashi, M.; Chikazawa, Y.; and Hori, T.; 2004. Short nap
versus short rest: recuperative effects during VDT work. Er-
gonomics, 47, 1549-1560.
Hayashi, M.; Motoyoshi, N.; and Hori, T.; 2005. Recupera-
tive power of a short daytime nap with or without stage 2
sleep. Sleep, 28, 829-836.
Hayashi, M.; and Hori, T.; 2007. A short nap as a counter-
measure against afternoon sleepiness, Japanese Journal of
Physiological Psychology and Psychophysiology, 25(1): 45-
59.
Lavie, P.; and Schulz, H.; 1985. Ultradian rhythms: gates of
sleep and wakefulness., Ultradian rhythms in physiology
and behavior. In Schulz, H; and Lavie, P.; (Eds.), Berlin:
Springer-Verlag, 148–164.
NHK Broadcasting Culture Research Institute, 2020. Na-
tional Daily Life Survey
Ministry of Health, Labour and Welfare, 2019. National
Health and Nutrition Survey
Stampi, C., Mullington, J.; Rivers, M.; Campos, J. P.; and
Broughton, R.; 1990. Ultrashort sleep schedules: Sleep ar-
chitecture and recuperative value of 80-, 50- and 20-min
naps. In J. Horne (Ed.), Sleep'90. Bochum: Pontenagel Press,
71-74.
Toma, A.; and Ogata, S.; 2004. Fundamental research to-
ward the education practice which applied music: con-
sciousness change on EEG under the music appreciation and
mental set. The bulletin of the Research and Clinical Center
for Handicapped Children, 6, 41-54
93