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International Journal of
Environmental Research
and Public Health
Article
The Effects of High-Temperature Weather on Human
Sleep Quality and Appetite
Guozhong Zheng *, Ke Li and Yajing Wang
School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003,
China; like@ncepu.edu.cn (K.L.); wangyajing@ncepu.edu.cn (Y.W.)
* Correspondence: zhengguozhong@ncepu.edu.cn; Tel.: +86-312-752-2443
Received: 14 December 2018; Accepted: 16 January 2019; Published: 18 January 2019
Abstract: High-temperature weather appears in high frequency, big strength, and long duration in the
summer. It is therefore important to study the effects of high-temperature weather on sleep quality
and appetite. Ten healthy college students were selected as subjects. The experiment conditions were
divided by the daily maximum temperature into 28 ◦ C, 32 ◦ C, 36 ◦ C, and 38 ◦ C. The objective sleep
quality was measured by an intelligent sleep monitoring belt, and the subjective sleep quality was
measured by a questionnaire survey. The subjective appetites were assessed by a visual analog scale
(VAS), and the objective appetites were assessed by the meal weight and the meal time. For sleep
quality, the objective results indicated that the sleep quality at 32 ◦ C was the best, followed by 28 ◦ C,
while the sleep quality at 36 ◦ C and 38 ◦ C was the worst. Significant effects were mainly reflected in
sleep duration and shallow sleep. The subjective results showed that temperature had significant
effects on sleep calmness, difficulty in falling asleep, sleep satisfaction, and sleep adequateness.
For appetite, the VAS results indicated that high temperatures mainly led to a reduction of appetite at
lunch time. The meal weights of lunch were larger than those of supper except for 28 ◦ C, and the
meal time of lunch and supper was longer than that of breakfast. The meal time of lunch was longer
than that of supper except for 36 ◦ C. This paper can provide a study method and reference data for
the sleep quality and appetite of human in high-temperature weather.
Keywords: high-temperature weather; sleep quality; appetite; meal time; meal weight
1. Introduction
An average person spends about one third of their life sleeping. Adequate sleep is beneficial to
restore physical strength and refresh the brain, and it helps to maintain good health and productivity of
the human body. Nevertheless, insufficient sleep may disrupt the body’s cognitive function and immune
function. For instance, sleep disorders can cause changes in immune mechanism-neuroendocrine-
thermoregulation, and then result in a pathological process [1,2]. In recent years, high-temperature
weather has shown the characteristics of high frequency, high intensity, and long duration [3,4]. To
begin with, high temperatures cause thermal discomfort to the human body, even at night, and affect
our quality of life [3–5]. In addition, high temperatures also suppress appetite. Food intake regulation
is a mechanism of thermoregulation, and the feeding activity of human body may be affected by
thermoregulatory response to prevent hyperthermia in a hot environment [6].
In actual life, a high-temperature environments is common when hot weather occurs [2]. In some
places, such as school classrooms, student dormitories, security pavilion and remote places, air
conditioners are not offered, people have to stay in these places for a long time and their sleep quality
and appetite are adversely affected by high temperatures [5–7]. Furthermore, insufficient sleep may
lead to frequent accidental injuries and huge economic losses [1], and the decreased appetite may cause
Int. J. Environ. Res. Public Health 2019, 16, 270; doi:10.3390/ijerph16020270 www.mdpi.com/journal/ijerphInt. J. Environ. Res. Public Health 2019, 16, 270 2 of 13
weight loss or malnutrition, thus finally affecting health [8]. Therefore, to ensure physiological health,
it is of great importance to study the effects of high-temperature weather on sleep quality and appetite.
Some scholars have studied the influence of temperature on the sleep quality of humans. Lan [9]
selected eighteen students without sleep disorders as subjects, and the temperature conditions were
set as 23 ◦ C, 26 ◦ C, and 30 ◦ C in a sleep chamber. A subjective questionnaire, physiological parameters,
and a measurement of work efficiency were adopted to evaluate sleep quality after getting up on
the next day. The results indicated that sleep quality at 26 ◦ C was the highest, and a higher or
lower temperature would activate the body thermoregulation system and affect the subjects’ sleep
quality. Pan [10] studied the thermal comfort of humans during sleep. The temperature conditions
were divided into a summer group (23 ◦ C, 26 ◦ C, and 30 ◦ C) and winter group (17 ◦ C, 20 ◦ C, and
23 ◦ C). College students were selected as subjects. A subjective questionnaire was carried out and
physiological parameters were measured. The results indicated that the temperature mainly affected
the duration of sleep onset latency (SOL) and slow wave sleep (SWS). Okamoto et al. [11] examined the
effects of mild heat exposure on sleep quality and the body temperature of elderly people. Ten healthy
male elderly people were selected as subjects, and they were asked to sleep from 22:00 to 06:00.
The environment conditions were set as: (1) 26 ◦ C, 50% and (2) 32 ◦ C, 50%. The electroencephalogram
(EEG), electrooculography (EOG), mental electromyogram, rectal temperature, and skin temperature
were continuously recorded. The tests indicated that, at 32 ◦ C, the awakening rate and the total
awakening time significantly increased, the duration of rapid eyes movement (REM) decreased,
the fall in rectal temperature was significantly suppressed, and the mean skin temperature increased.
Lan et al. [12] summarized that high temperatures resulted in decreased total sleep time, decreased
duration of REM and SWS, and increased sleep onset latency (SOL) and wake after sleep onset (WASO).
Zhu et al. [13] measured the environmental parameters of different bedrooms (including naturally
ventilated rooms and air-conditioned rooms) for nearly one month during the summer in Beijing.
Subjects’ sleep quality was monitored by Actiwatch 2 (Philips Respironics, Pittsburgh, Pennsylvania,
USA). The results showed that in naturally ventilated rooms, temperature was significantly correlated
to sleep efficiency, WASO, total sleep time, and number of awakenings. As shown in the above
literature, the effects of temperature on sleep quality were reflected in several aspects. Firstly, the higher
temperature would activate the body thermoregulation system and stress hormones were produced
by central neuronal cells, then it resulted in increased wakefulness, and sleep quality was affected.
Secondly, the SOL and SWS were affected by high temperatures, which caused a decreased duration of
SWS and increased SOL. Lastly, the decrease of core temperature was significantly suppressed.
Some scholars have also conducted some studies on the appetite of humans. Wang [14] studied
the effect of physical exercise on human appetite and food rations. Seven healthy males were selected
as subjects, and they were asked to jog and swim under the same energy expenditure. Then, their oral
temperatures were measured after 10 min of exercise. Half an hour after the exercise, their appetite
and food intake were tested using an appetite scale (7 grades). The results showed that compared to
swimming, the average body temperature increased and the appetite reduced in jogging condition.
Westerterp-Plantenga et al. [15] assessed the effect of a short exposure to the thermoneutral temperature
of 27 ◦ C and the normal temperature of 22 ◦ C on the energy metabolism in women. Eight healthy
female volunteers participated in this study, and they were required to stay in the breathing room for
48 h. Then, they were fed in energy balance during the first 24 h, and fed ad libitum during the next
24 h. Their appetite was recorded by a visual analog scale (VAS), while their skin temperatures and core
temperatures were measured continuously by thermistor probes. The results showed that compared
with 22 ◦ C, the respiratory quotient, the core temperature and the skin temperature all increased, while
the differences between the rectal temperature and the distal temperature decreased. The reduction
in energy intake was primarily related to the increase of body temperature. Geeraerts et al. [16]
investigated the effect of experimentally induced anxiety on the gastric sensory–motor function of
healthy people. In the experiment, the gastric sensitivity and accommodation ability of 14 subjects
were evaluated by a gastric pressure instrument. Moreover, they were asked to carry out a full drinkingInt. J. Environ. Res. Public Health 2019, 16, 270 3 of 13
test (30 mL/min) while epigastric symptoms were recorded by a VAS scale. The results indicated that
anxiety led to a significant decrease in gastric compliance, and anxiety was significantly associated
with a higher score of satiety, fullness, and satisfaction. To sum up, appetite was inhibited by high
temperatures. On one hand, high temperatures led to a high core body temperature, then the increased
core body temperature caused poor appetite and reduced energy intake. On the other hand, anxiety
was associated with high temperatures and led to a higher fullness and satisfaction.
In this study, sleep quality and human appetite were adopted to study the quality of life in
high-temperature weather. Ten key sleep quality parameters were adopted to evaluate objective sleep
quality, and a combined subjective questionnaire was used to comprehensively evaluate subjective
sleep quality. A VAS scale was used to assess the subjective appetite, and the meal weight and meal
time were adopted to assess the objective appetite.
This study mainly differs from previous studies in the following aspects: (1) providing both an
objective method and a subjective method to evaluate sleep quality and appetite; (2) adopting meal
weight and meal time to assess objective appetite; (3) adding food grease into a new VAS scale to
measure the degree of greasiness of the food.
2. Materials and Methods
2.1. Subjects
A total of ten college students, including five males and five females, were selected as subjects.
The subjects should be in good health condition and have no diseases, such as hypertension, sleep
disorders, and so on. During the experiment, all subjects were not allowed to drink coffee, drink
alcohol, and take drugs. Table 1 shows the anthropometric information of the subjects.
Table 1. Anthropometric information of subjects.
Gender Age (years old) Height (cm) Weight (kg) BMI a (kg/m2 )
Male 22.4 ± 1.7 172.2 ± 5.1 69.2 ± 12.2 23.2 ± 2.9
Female 23.0 ± 1.4 161.4 ± 4.7 53.8 ± 8.1 20.6 ± 2.8
a Body mass index; BMI = weight/height2 , normally between 18 and 25 kg/m2 .
The sample size of the subjects was considered and determined as follows: (1) The sample sizes
of related literature on human experiments varied from 7 to 14 [17–21], thus ten subjects were initially
selected for this study; (2) the statistical power of the sample size (n = 10) was calculated by the PASS
software (NCSS, Kasville, Utah, USA) to show the power of statistical analyses. The results indicated
that the statistical power value of the paired sample t test of ten subjects was 0.940. This shows that
10 subjects would provide sufficient statistical power to detect a difference.
All participants provided written informed consent, and they were informed of the study
purpose. The study was approved by the Chinese Ethics Committee of Registering Clinical Trials
(No. ChiECRCT-20170108) and conformed to the principles outlined in the Declaration of Helsinki.
2.2. Experiment Conditions
There was a positive correlation between temperature and heat-related diseases [22–26]; therefore,
the daily maximum temperature displayed more strength in reflecting the effects of the environment
intensity on the human body, therefore it provided a more spatially robust measure of heat stress.
Thus, in this study, the experiment conditions were divided by the daily maximum hourly outdoor
temperature, namely 28 ◦ C, 32 ◦ C, 36 ◦ C, and 38 ◦ C (the maximum hourly outdoor temperature ±
1.0 ◦ C), respectively. Each temperature condition represents a high-temperature day. The experiments
were conducted in a top floor non-air-conditioned house in Baoding, and the house maintained natural
ventilation during the experiment.Int. J. Environ. Res. Public Health 2019, 16, 270 4 of 13
Int. J. Environ. Res. Public Health 2019, 16, x 4 of 13
Most experiments of related literature were conducted in an experiment chamber. In this study,
the experiment
h. If the experiments was conducted in an actualin
are conducted site.an
Theexperimental
experiment chamber can supply
chamber, idealmay
there temperature
be issues of
control; however, the space in the chamber is closed and narrow, and it cannot supply natural daylight.
psychological anxiety, fuzziness, impatience, and other abnormal emotions, and finally influence the
In this study, the experiment duration of each temperature condition lasted for 24 h. If the experiments
experiment results. For actual site, although the temperature is affected by the weather, if the
are conducted in an experimental chamber, there may be issues of psychological anxiety, fuzziness,
experiment day and
impatience, is well-selected,
other abnormal the above problems
emotions, and finallycan be avoided.
influence In this study,
the experiment results.all experiments
For actual in
different temperature
site, although conditionsiswere
the temperature conducted
affected on sunny
by the weather, if the days in theday
experiment summer. Although the
is well-selected,
maximum temperatures
the above problems can were different,
be avoided. In this the
study,changing trends
all experiments of the temperature
in different outdoor temperature
conditions were
similar. To choose the experiment day of a certain temperature condition, the hourlydifferent,
were conducted on sunny days in the summer. Although the maximum temperatures were temperature of
the changing
the weather trends before
forecast of the outdoor temperature were
the experiment day similar. To choose the
was consulted. experiment
When that day
metofthe
a certain
experiment
temperature condition, the hourly temperature of the weather forecast before the experiment day was
condition, the experiment was then conducted in the next day. When conducting the experiment, the
consulted. When that met the experiment condition, the experiment was then conducted in the next
hourly outdoor temperature of the experiment day was also measured to verify the experiment
day. When conducting the experiment, the hourly outdoor temperature of the experiment day was
condition. When the
also measured measured
to verify hourly outdoor
the experiment condition.temperature
When the measuredmet thehourly
requirement of the experiment
outdoor temperature
condition,
met thethe experiment
requirement condition
of the experiment was finished.
condition, the Otherwise, the experiment
experiment condition of this
was finished. temperament
Otherwise,
condition was to beof
the experiment reconducted. The flowchart
this temperament condition was to select an experiment
to be reconducted. Theday of a certain
flowchart temperature
to select an
experiment day of a certain
condition is shown in Figure 1. temperature condition is shown in Figure 1.
To start an experiment of a certain temperature condition
Consult the weather forecast before the experiment day
NO Does the temperature meet the
requirement of the experiment
condition?
YES
Conduct the experiment of this temperature condition
Measure the hourly outdoor temperature
Does the measured temperature meet
the requirement of the experiment
condition?
YES
The experiment of this temperature condition is finished
Figure
Figure 1. Flowchart
1. Flowchart totoselect
selectan
an experiment
experiment day
dayof of
a certain temperature
a certain condition.
temperature condition.
2.3. Experiment Instruments
2.3. Experiment Instruments
The parameters and instruments in the experiment are summarized in Table 2.
The parameters and instruments in the experiment are summarized in Table 2.
Table 2. Parameters and instruments.
Parameter Instrument Model Precision
Outdoor temperature Thermal index meter AZ8778 ±0.6 °C
Objective sleep quality Sleep monitoring belt Z101 /Int. J. Environ. Res. Public Health 2019, 16, 270 5 of 13
Table 2. Parameters and instruments.
Parameter Instrument Model Precision
Outdoor temperature Thermal index meter AZ8778 ±0.6 ◦ C
Objective sleep quality Sleep monitoring belt Z101 /
Subjective sleep quality Sleep questionnaire / ±0.1 ◦ C
Meal weight Electronic scale EK813 ±1 g
Meal time Watch / ±1 min
Subjective appetite VAS scale / /
2.4. Sleep Quality
In the experiments, a monitoring belt was used to measure objective sleep quality. It is a
nonwearable intelligent sleep monitoring belt which is laid on the mattress. It can monitor some
physiological parameters, such as heart rate, respiratory rate, turn over, and sleep cycle in real time.
Then, the sleep quality data can be obtained from the software of Sleepace. Ten key objective evaluation
indices, including sleep latency, actual sleep time, total sleep time, awakening frequency, deep sleep,
moderate sleep, light sleep, awake phase, average heart rate, and average respiratory rate, can be
obtained. When using the monitoring belt, subjects do not need to change their sleep habits.
The sleep questionnaire [27] was adopted to measure the subjective sleep quality in this paper.
The questionnaire is shown in Table 3. The qualitative features of sleep were characterized by items 1
to 6, which included calmness of sleep, ease of falling asleep, ease of awakening, freshness after
awakening, satisfaction about sleep, and sufficient sleep [27]. Items 7 to 9 characterized the quantitative
features of sleep, which included time required for falling asleep, frequency of waking at night, and
duration of each waking up. All items used 5 points except for item 6, which used a two-level score.
For all items, the higher the level is, the better the sleep quality is [10,27].
Table 3. Items of the sleep quality questionnaire.
Score
Questions
5 4 3 2 1 0
How is your habitual Neither calm Quite
Very calm Fairly calm Very restless /
sleep like? nor restless restless
How is falling asleep Neither easy Quite
Very easy Fairly easy Very difficult /
usually like? nor difficult difficult
Neither easy Quite
How is waking up usually like? Very easy Fairly easy Very difficult /
nor difficult difficult
Do you usually feel refreshed
Fully Fairly Moderately Not much Not at all /
after awakening?
Are you usually satisfied with
Fully Fairly Moderately Not much Not at all /
your sleep?
Do you think you get
/ / / / Yes No
enough sleep?
How long does it usually take
30 min /
you to fall asleep?
Do you usually wake up at
Never Seldom Sometimes Often Always /
night-time?
How long do you stay awake
02.5. Appetite
In the experiment, a subjective index and objective index for appetite measurement were both
considered. For subjective parameters, a visual analog scale (VAS) was used to quantify a subject’s
feelings on desire to eat, hunger, prospective consumption, and fullness [28,29]. To measure the
greasiness degree
Int. J. Environ. ofPublic
Res. the food,
Health food greasiness
2019, 16, 270 was added in the VAS. The scale 0–10 was adopted to6 of 13
evaluate the sensation before or after eating, and the higher the scale, the stronger the sensation.
Based on their experience, the subjects were free to calibrate on each line that best matched how they
werefeeling
feelingat at the
the time. The VAS
time. The VAS questionnaire
questionnaire is
isshown
shownin inTable
Table4.4.Among
Amongthese
theseitems,
items, the
the feeling of
feeling
fullness was evaluated after the meals, while the other items were evaluated before
of fullness was evaluated after the meals, while the other items were evaluated before the meals. the meals.
Table 4. The VAS questionnaire.
Table 4. The VAS questionnaire.
Item VAS Scale
Item VAS scale
Int.
Int. J. Environ. Res. Public Health 2019, 16, x 66 of 13
Int. J.
J. Environ.
Environ. Res.
Res. Public
Public Health 2019,
2019, 16,
HealthDesire 16, xx
to eat 6 of
of 13
13
Desire to eat
Hunger
Hunger Hunger
Prospective
Prospective consumption
Prospective consumption
consumption
Fullness
Fullness Fullness
Food greasy Food greasy
Food greasy
For
For objective
objective measurement,
measurement,
For objective measurement,the
the meal
meal weight
weight
the meal weightand
and the
andmeal
the meal time were
time time
the meal adopted.
werewere
adopted. The
The meal
adopted. meal weight
weight
The meal weight
was measured
was measured
was measured by an electronic
by anbyelectronic scale before
scalescale
an electronic before and after
and after
before meals.
meals.
and after The duration
The duration
meals. used for
usedused
The duration the
for the whole
forwhole meal
mealmeal
the whole
was recorded
was was
recorded to
recordedto measure
measure the meal
thethe
to measure meal time.
time.
meal At
AtAt
time. all
allalltemperature
temperatureconditions,
temperature conditions,breakfast
conditions, breakfast contained
breakfast milk,
contained milk,
milk, eggs,
eggs, and
eggs,and bread,
andbread, lunch
bread,lunch contained
lunchcontained
containedricerice and
andaaafried
riceand fried dish,
frieddish, and
dish,and supper
andsupper contained
suppercontained noodles
containednoodles and
noodlesand sausages.
andsausages.
sausages.Thus,
Thus, the
Thus,the caloric
thecaloric
caloric content
content
content of
of of the
thethe three
three
three meals
meals was
waswas
meals constant
constant
constant under
under the
the the
under four
fourfour temperature
temperature conditions.
conditions.
temperature In
In addition,
conditions. In
addition,
addition, all
all ofall of the
theofmeals meals
the meals were
werewere provided
provided
provided in advance.
in advance.
in advance.
2.6.
2.6. Experiment Process
2.6. Experiment
Experiment Process
Process
For
For each
each experiment
For each experiment
experiment day, subjects
day, day, were
subjects
subjects werewereasked
askedaskedto
to arrive at
at the
to arrive
arrive theatexperiment
the experiment
experiment house
house at
at 08:30,
house then
at 08:30,
08:30, then then
rest quietly
rest for
quietly 30forminutes
30 min to calm down their
their physiological
physiological state.
rest quietly for 30 minutes to calm down their physiological state. The experiment continued from09:00
state. The
The experiment
experiment continued
continued from
from
09:00
09:00to to 09:00
to09:00
09:00 on on
on the
the next
next day.
day. Furthermore,
Furthermore,the
Furthermore, theintervals
the intervalsbetween
intervals betweeneach
between eachtemperature
each temperature
temperature condition
condition
condition lasted
lasted at
lasted
at
at least
least
least four
four
four days,
days,
days, andandall
and allallsubjects’
subjects’sleep
subjects’ sleepand
sleep andappetite
and appetite were
appetite were recorded
were recorded at the
at the same
the same experiment
sameexperiment
experimenthouse house
houseon all
on
on all temperature
alltemperature conditions.
temperatureconditions.
conditions.During During
Duringthe the experiment
theexperiment
experimentperiod, period, subjects
period,subjects
subjectswere were required
requiredtoto
wererequired stay
stay
to stay inin
thethe
in house,
the
house,
house,and and
andthey they
they could
could
could rest
rest or or
rest or engage
engage
engage in
in in mental
mental
mental activities,
activities,
activities, suchsuch
such as
as as reading
reading
reading or oror writing.
writing.
writing.
When When measuring
measuring sleep quality,
sleep quality, bamboo
bamboo mats
When measuring sleep quality, bamboo mats were used. All subjectscould
mats were
were used.
used. All
All subjects
subjects could
could freely
freely addadd
freely or
or decrease
add or
decrease
decrease the
the number number
the number of
of their their
clothes
of their clothes and
and quilts.
clothes quilts. The
The subjects
and quilts. subjects
The subjects could
couldcould
choose choose their
their bedtime
choose bedtime according
according
their bedtime to their
according to
tosleep
their sleep
sleep habits.
their habits. Before Before
habits. bedtime,
Before bedtime,
subjectssubjects
bedtime, were asked
subjects were
were toasked
lay theto
asked lay
lay the
the monitoring
tomonitoring belt on thebelt
monitoring on
on the
mattress
belt mattress
thenear their chest
mattress
near their
near and chest
chest and
theirabdomen. abdomen.
andThen,
abdomen. Then,
Then, the
the monitor was
the monitor
turnedwas
monitor on and
was turned
turned on
on andand the
the parameters the parameters
were recorded.
parameters were recorded.
wereAfter getting up
recorded.
After getting
Afteringetting
the next up in the
upmorning, next
in the next morning,
the morning,
monitor was the monitor
the turned
monitoroff. was
was turned
In addition,
turned off. off.
the In addition,
Insubjects
addition, the
were subjects
theasked
subjects were
to fill
wereout the
asked to
to fill
askedsleep out
out the
fillquality sleep
sleep quality
quality questionnaire.
thequestionnaire. questionnaire.
To
To measure
To measure
measure appetite,
appetite,
appetite, the
the thesubjects
subjects
subjects werewere
were asked
asked
asked to
totohave
havebreakfast,
have breakfast,lunch,
breakfast, lunch, and
lunch, supper
and supper
and supper at at 08:00,
at08:00,
08:00,12:30,
12:30,
12:30,and and
and18:30 18:30 separately.
separately.
18:30 Before
BeforeBefore
separately. each
each meal,
eachthe meal, the
subjects
meal, the weresubjects were
askedwere
subjects asked
to fill asked
out thetoto
VASfill out
out the VAS
the
fillquestionnaire. VAS Before
questionnaire.
and after Before
the and
meals, theafter the
weights meals,
of the the weights
foods were of the
measured,
questionnaire. Before and after the meals, the weights of the foods were measured, and the meal foods andwere the measured,
meal weightsand the
were meal
obtained
weights
fromwere
weights obtained
the weight
were obtained from
from the
differences. the weight
Meanwhile,
weight differences.
the timeMeanwhile,
differences. used for thethe
Meanwhile, whole
the time
timemealused
usedwasfor the
the whole
wholetomeal
for recorded measure
meal
was
was recorded
the meal time.
recorded to
to measure
measure the the meal
meal time.
time.
In
In addition,
In addition,
addition, during
during
during each
each eachexperiment
experiment
experiment group
groupof
group of aaa certain
of certain temperature
certaintemperature condition,
temperaturecondition,
condition, thethe hourly
hourly
the hourlyoutdoor
outdoor
outdoor temperatures
temperatures
temperatures were
werewere
measuredmeasured
measured every every hour
hourhour
every in the in the continuous
incontinuous
the continuous 24
24 h.24 hours.
The The
results
hours. Theareresults
shown
results are shown
areinshown
Figure 2.
in
in Figure
Figure 2. 2.Int. J. Environ. Res. Public Health 2019, 16, 270 7 of 13
Int. J. Environ. Res. Public Health 2019, 16, x 7 of 13
38
28℃
37 32℃
36 36℃
35 38℃
34
Outdoor temperature (℃) 33
32
31
30
29
28
27
26
25
24
23
22
:00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00 :00
09 10 1 1 12 13 14 15 16 17 1 8 19 20 21 2 2 23 24 0 1 0 2 03 04 0 5 0 6 07 08 0 9
Time (h)
2. The hourly outdoor temperature of the four temperature conditions.
Figure 2.Figure
The hourly outdoor temperature of the four temperature conditions.
2.7. Statistical Method
2.7. Statistical Method
Since the sample size was less than 50, the normal tests of the measuring data among temperature
conditions were conducted using the Shapiro-Wilk test. The test rejects the hypothesis of normality
Since when
the the
sample
p-value issize wasor less
less than than
equal to 50, the
0.05. When normal
comparing tests ofdata
the measuring the measuring
among temperaturedata among
temperature conditions
conditions, were
if the two setsconducted using the
of data were normally Shapiro-Wilk
distributed, the pairedtest. The
sample test
t test wasrejects
used. If the
the hypothesis
two sets of data did not follow normal distribution, then a two-pair sample
of normality when the p-value is less than or equal to 0.05. When comparing the measuring data test in nonparametric
tests should be used. p-values less than 0.05 were considered statistically significant. In this paper, six
among temperature conditions, if the two sets of data were normally distributed, the paired sample
paired of tests were done, including 28–32 ◦ C, 28–36 ◦ C, 28–38 ◦ C, 32–36 ◦ C, 32–38 ◦ C, and 36–38 ◦ C.
T test was used. If the two sets of data did not follow normal distribution, then a two-pair sample
3. Results
test in nonparametric tests should be used. p-values less than 0.05 were considered statistically
significant. 3.1.
In this paper,
The Effects six paired
of Temperature of tests
on Sleep were done, including 28–32 °C, 28–36 °C, 28–38 °C, 32–36
Quality
°C, 32–38 °C, and The 36–38 °C. of objective assessment of sleep quality and temperature are shown in Figures 3
relationships
and 4. The actual sleep time, total sleep time, shallow sleep, average heart rate, and average respiration
3. Results rate were influenced by temperature. Furthermore, the actual sleep time and total sleep time at 32 ◦ C
were significantly longer than those at 28 ◦ C (p < 0.05); the actual sleep time and total sleep time at
36 ◦ C were significantly shorter than those at 32 ◦ C (p < 0.05); and the total sleep time at 36 ◦ C were
3.1. The Effects of Temperature
significantly shorter than onthose
Sleepat Quality
28 ◦ C (p < 0.05). The average heart rate at 36 ◦ C was significantly
larger than that at 28 C (p < 0.05), and the shallow sleep and average respiration rate at 36 ◦ C were
◦
The relationships of objective
significantly larger than thoseassessment
at 28 ◦ C and 32of ◦sleep
C (p < quality
0.05). Theand temperature
actual sleep time at are38 ◦shown
C was in Figures
3 and 4. The actual shorter
significantly sleepthan time,that total
at 28 ◦ Csleep
and 32time, shallow
◦ C, while the total sleep, average
sleep time heart
at 38 ◦ C was rate, and average
significantly
shorter than that at 32 ◦ C (p < 0.05). The shallow sleep at 38 ◦ C was significantly larger than thatand
at total sleep
respiration rate were influenced by temperature. Furthermore, the actual sleep time
32 ◦ C (p < 0.05). However, there was no significant difference between 36 ◦ C and 38 ◦ C (p < 0.05).
time at 32 °C were significantly longer than those at 28 °C (p < 0.05); the actual sleep time and total
The results indicate that sleep quality at 32 ◦ C was the best, followed by 28 ◦ C, and that at 36 ◦ C and
sleep time at
38 ◦36 °C the
C was were significantly
worst. The significantshorter
effects of than those at 32
high temperatures on°C (pquality
sleep < 0.05);
were and thereflected
mainly total sleep time at
36 °C were significantly shorter than those at 28 °C (p < 0.05). The average heart rate at 36 °C was
in the duration of sleep and shallow sleep.
significantly larger than that at 28 °C (p < 0.05), and the shallow sleep and average respiration rate at
36 °C were significantly larger than those at 28 °C and 32 °C (p < 0.05). The actual sleep time at 38 °C
was significantly shorter than that at 28 °C and 32 °C, while the total sleep time at 38 °C was
significantly shorter than that at 32 °C (p < 0.05). The shallow sleep at 38 °C was significantly larger than
that at 32 °C (p < 0.05). However, there was no significant difference between 36 °C and 38 °C (p < 0.05).
The results indicate that sleep quality at 32 °C was the best, followed by 28 °C, and that at 36 °C and
38 °C was the worst. The significant effects of high temperatures on sleep quality were mainlyInt. J. Environ. Res. Public Health 2019, 16, x 8 of 13
Int. J. Environ. Res. Public Health 2019, 16, 270 8 of 13
Int. J. Environ. Res. Public Health 2019, 16, x 8 of 13
8 Sleep onset latency 1.5
▲ The actual length of sleep
8 Sleep
Total sleeponset
timelatency 1.5
7 ▲ The actual
Awakening length of sleep
times
▲
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7 Awakening times
▲
6 ▲◆ ◆
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◆ ▲◆
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4
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4
3
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2
1
1
0 0.0
28℃ 32℃ 36℃ 38℃
0 Temperature (℃) 0.0
28℃ 32℃ 36℃ 38℃
Temperature (℃)
Figure 3. Sleep onset latency, actual length of sleep, total sleep time, and awakening time at 28 °C, 32 °C,
Figure
36°C, Sleep
3.38°C
and3. onset
(The latency,
legend actual length
▲ indicates thatof sleep,istotal sleep time, and awakening at 28 ◦ C,
timewith °C32
◦ C,
Figure
◦
Sleep ◦
onset latency, actual length ofthere a significant
sleep, total difference
sleep time, compared
and awakening time at 2828°C, 32(p°C,
28 ◦ C
Article
36 of
< 0.05), C,High-Temperature
and 38 C◆(The legend N there
indicates that there is a significant difference compared < with
The Effects36°C,theandlegend
38°C (Theindicates that
Weather
legend on is athat
Human
▲ indicates significant
there is difference compared
a significant with
difference 32 °C (p with
compared 0.05)).
28 °C (p
(p < 0.05),
Sleep Quality and the legend ◆ indicates that there is a significant difference compared with 32 ◦ C (p < 0.05)).
Appetite
< 0.05), the legend ◆ indicates that there is a significant difference compared with 32 °C (p < 0.05)).
Guozhong Zheng *, Ke Li and Yajing Wang
60
School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, ▲ 65 Deep sleep
China; like@ncepu.edu.cn (K.L.); wangyajing@ncepu.edu.cn (Y.W.) Moderate sleep
* Correspondence: zhengguozhong@ncepu.edu.cn; Tel.: +86-312-752-2443
55 60
Received: 14 December 2018; Accepted: 16 January 2019; Published: date
▲ 60 65 Deepsleep
Shallow sleep
Moderate sleep
Awakening
Proportion of different sleep stage (％)
50 55
Abstract: High-temperature weather appears in high frequency, big strength, and long duration in 55 60 Shallow
Heart rate sleep
the summer. It is therefore important to study the effects of high-temperature weather on sleep Awakening
Respiration rate
Proportion of different sleep stage (％)
quality and appetite. Ten healthy college students were selected as subjects. The experiment
45 50 50 55 Heart rate
Heart/Respiration rate (bpm)
conditions were divided by the daily maximum temperature into 28 °C, 32 °C, 36 °C, and 38 °C.
The objective sleep quality was measured by an intelligent sleep monitoring belt, and the subjective Respiration rate
45 50
Heart/Respiration rate (bpm)
sleep quality was measured by a questionnaire survey. The subjective appetites were assessed by a
40 45
visual analog scale (VAS), and the objective appetites were assessed by the meal weight and the meal
time. For sleep quality, the objective results indicated that the sleep quality at 32 °C was the best,
40 45
35 40
followed by 28 °C, while the sleep quality at 36 °C and 38 °C was the worst. Significant effects were
mainly reflected in sleep duration and shallow sleep. The subjective results showed that temperature
had significant effects on sleep calmness, difficulty in falling asleep, sleep satisfaction, and sleep 35 40
30 35
adequateness. For appetite, the VAS results indicated that high temperatures mainly led to a
reduction of appetite at lunch time. The meal weights of lunch were larger than those of supper
except for 28 °C, and the meal time of lunch and supper was longer than that of breakfast. The meal
30 35
25 30
time of lunch was longer than that of supper except for 36 °C. This paper can provide a study method
and reference data for the sleep quality and appetite of human in high-temperature weather. ▲◆ 25 30
20 25
Keywords: high-temperature weather; sleep quality; appetite; meal time; meal weight ▲◆ ◆
20 25
▲◆
15 20 ◆
15 20
1. Introduction ▲◆
An average person spends10 15one third of their life sleeping. Adequate sleep is beneficial to
about 10 15
restore physical strength and refresh the brain, and it helps to maintain good health and
5 10
productivity of the human body. Nevertheless, insufficient sleep may disrupt the body’s cognitive
function and immune function. For instance, sleep disorders can cause changes in immune 5 10
mechanism-neuroendocrine-thermoregulation, and then result in a pathological process [1,2]. In
0 5
recent years, high-temperature weather has shown the characteristics of high frequency, high 0 5
28℃ 32℃
intensity, and long duration [3,4]. To begin with, high temperatures cause thermal discomfort to the
36℃ 38℃
Temperature (℃)
human body, even at night, and affect our quality of life [3–5]. In addition, high temperatures also
0
suppress appetite. Food intake regulation is a mechanism of thermoregulation, and the feeding 0
28℃ 32℃
activity of human body may be affected by thermoregulatory response to prevent hyperthermia in a 36℃ 38℃
hot environment [6].
Figure 4. The average heart rate, average Temperature
In actual life, a high-temperature environments is common when hot weather occurs [2]. In respiration (℃)rate, and proportion of deep sleep, moderate
Figure 4. The average heart rate, average respiration
some places, such as school classrooms, student dormitories, security pavilion and remote places,
sleep, shallow sleep, and awakening, at 28 C,The ◦Article ◦ rate, ◦
C, 36 and
32 Effects proportion
38 ◦ C (The
C,High-Temperature
and of deeplegend sleep, moderate
N indicates
air conditioners are not offered, people have to stay in these places for a long time and their sleep
of Weather on Humanthat
sleep, shallow
Figureis 4.
there sleep,
The average
a significant and awakening,
heart rate,
difference at 28
averagewith
compared °C,
quality and appetite are adversely affected by high temperatures [5–7]. Furthermore, insufficient sleep
32 °C,
respiration
may lead to frequent accidental injuries and huge economic losses [1], and the decreased appetite may
◦ 36
28 CQuality
Sleep
°C,
(prate, and and
< 0.05),andthe
38 °C (The
proportion legend
legend ◆ofindicates
Appetite
▲
deep sleep, indicates
that moderate
there thatis a
there is a significant difference compared with
cause weight loss or malnutrition, thus finally affecting health [8]. Therefore, to ensure physiological
sleep, shallow
significant sleep, and
difference awakening,
compared with 32 at ◦28 C (p 28 °C
°C,Int. J. Environ. Res. Public Health 2019, 16, x 9 of 13
Int. J. Environ. Res. Public Health 2019, 16, 270 9 of 13
4.5
28℃
4.0 32℃
3.5 36℃
Grading level
38℃
3.0 ▲
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e e e g p ep e s ep
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◦ C, 32 ◦ C, 36 ◦ C, and 38 ◦ C (The legend
Figure 5. The subjective evaluation results of sleep quality at 28The
Article
Effects of High-Temperature Weather on Human
Figure 5. The subjective
N indicates that there isevaluation
a significantresults of compared
difference sleep quality at
28 28
withSleep °C,< 32
◦ CQuality
(p 0.05),
and °C,the 36legend
Appetite °C, and 38 °C (The
◆ indicates
legendthat▲ indicates
there that there
is a significant is a significant
difference compareddifference
with 32 ◦ Ccompared
(p < Guozhong
0.05)).Zheng with *, Ke 28
Li and°C (pWang< 0.05), the legend ◆
Yajing
indicates that there is a significant difference compared with School 32 of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003,
°C (p < 0.05)).
China; like@ncepu.edu.cn (K.L.); wangyajing@ncepu.edu.cn (Y.W.)
3.2. The Effects of Temperature on Appetite * Correspondence: zhengguozhong@ncepu.edu.cn; Tel.: +86-312-752-2443
Received: 14 December 2018; Accepted: 16 January 2019; Published: date
3.2. The Effects of Temperature
The relationships on Appetite
of objective appetite and temperature are
Abstract: shownweather
High-temperature in appears
Table in high5. Atbigthe
frequency, strength,four
and long duration in
the summer. It is therefore important to study the effects of high-temperature weather on sleep
temperature conditions, the meal weights of the breakfast were 389.8–447.2 g, and there was little
quality and appetite. Ten healthy college students were selected as subjects. The experiment
The relationships of objective appetite and temperature are shown inby anTable 5.monitoring
At belt,the
conditions were divided by the daily maximum temperature into 28 °C, 32 °C, 36 °C, and 38 °C.
The objective sleep quality was measured intelligent sleep and the four
subjective
difference among the four temperature conditions. The meal weights of the
sleep quality was measured by alunch
questionnaire were
survey. The507.7–614.6
subjective appetites wereg,assessed by a
temperature conditions, the meal weights of the breakfast
while the meal weights of the supper were 471.4–570.9 g, which were
visual 389.8–447.2
analog scale
indicates g,
(VAS), and the objective appetites
that the and there
were assessed
meal was
by the meal little
weight and the meal
time. For sleep quality, the objective results indicated that the weights
sleep quality at 32of°C was the best,
difference among
lunch were thethan
larger fourthose
temperature
of supperconditions.
except for 28The
◦ C. meal weights
The meal time
mainly reflected
of theandlunch
ofduration
in sleep breakfast was
shallow sleep.
were 8.5–11.6
The subjective
507.7–614.6
followed by 28 °C, while the sleep quality at 36 °C and 38 °C was the worst. Significant effects were
min,
results showed
g,
that temperature
had significant effects on sleep calmness, difficulty in falling asleep, sleep satisfaction, and sleep
whileandthe meal
there wasweights
also littleofdifference
the supper were
among the471.4–570.9 g, which
four temperature conditions.
adequateness. indicates
For appetite,The that
the VASmeal the that
time
results indicated meal
ofhighlunch weightsand
temperatures mainly led ofto a
reduction of appetite at lunch time. The meal weights of lunch were larger than those of supper
lunch werewas
supper larger than
longer those
than that of supper except
of breakfast, for
and the 28 time
meal °C. The
of lunch
except for mealwas
28 °C, and time
the longer
meal time of breakfast
of lunch than that of
and supper was longer was supper
than that 8.5–11.6
of breakfast.
time of lunch was longer than that of supper except for 36 °C. This paper can provide a study method
The meal
◦
mins,except
and there
for 36 wasC. Italso
waslittle difference
10.6–19.8 amongwhile
min at lunch, the four
it wastemperature
12.6–15.7 min conditions.
at supper, and Thethere mealwas time of
and reference data for the sleep quality and appetite of human in high-temperature weather.
Keywords: high-temperature weather; sleep quality; appetite; meal time; meal weight
lunchlittle
anddifference
supper was among the four
longer thantemperature conditions.
that of breakfast, and the meal time of lunch was longer than that
of supper except for 36 °C. It was 10.6–19.8 mins at lunch, while it was 12.6–15.7 mins at supper, and
1. Introduction
Table 5. The objective appetite in the four temperature conditions.
there was little difference among the four temperature conditions. An average person spends about one third of their life sleeping. Adequate sleep is beneficial to
restore physical strength and refresh the brain, and it helps to maintain good health and
productivity of the human body. Nevertheless, insufficient sleep may disrupt the body’s cognitive
The relationships of subjective appetite and temperature Objective arefunction.
function and Appetite
immune shown For instance,insleepTable
disorders can6. causeSubjects’
changes in immune
Index Meal ◦ ◦
mechanism-neuroendocrine-thermoregulation, and then result in a pathological process [1,2]. In
◦ ◦
appetite for lunch was significantly affected 28 byC temperature. The and
32 Cintensity, desire 36toCeat, hunger,
recent years, high-temperature
38and C prospective
weather has shown the characteristics of high frequency, high
long duration [3,4]. To begin with, high temperatures cause thermal discomfort to the
human body, even at night, and affect our quality of life [3–5]. In addition, high temperatures also
consumption at 36 °C were significantly
Breakfast lower
398.9 than 389.8
± 170.1 those±at 32 °C.
160.5
suppress Fullness
447.2
appetite. Food ± 182.4
intake at 38
regulation °C was
389.8
is a mechanism 153.5significantly
±of thermoregulation, and the feeding
activity of human body may be affected by thermoregulatory response to prevent hyperthermia in a
lower thanMealthat
weight
at (g) Lunchfullness
32 °C, and at ±32178.6
529.1 °C was 614.6 ± 240.1
significantly
hot environment507.7 ± 225.1
[6].higher than 568.2
that ±at146.9 28 °C. Food
Supper 570.9 ± 321.2 567.8 ± 266.9 471.4 ± 159.9 530.7 ± 165.9
In actual life, a high-temperature environments is common when hot weather occurs [2]. In
greasiness at 38 °C and 36 °C was lower than that at 32 °C,airand food greasiness at 32 °C was higher
some places, such as school classrooms, student dormitories, security pavilion and remote places,
conditioners are not offered, people have to stay in these places for a long time and their sleep
Breakfast 9.4 ± 4.2 10.9 ± 2.9
quality and appetite11.6 ± 4.3
are adversely 8.5 ± [5–7].
affected by high temperatures 4.2Furthermore, insufficient sleep
than that at 28 °C. The fullness of supper at 38 °C was
13.3 ± 8.2
significantly lower
may lead to frequent accidental
19.8 ± 7.9 ± 3.9
than
injuries and that
huge economic losses at 32
[1], and °C. appetite
the decreased Thismay
Meal time (min) Lunch cause weight loss 10.6
or malnutrition, thus finally affecting health±
16.9 [8]. 3.9
Therefore, to ensure physiological
indicates that the subjective appetite
Supper for lunch
12.6 ± 3.2 at 32 °C was
14.9 ± 6.8 the best. This
15.7 ± 5.4 result is similar
14.1 ± 5.5 to that for
Int. J. Environ. Res. Public Health 2019, 16, x; doi: www.mdpi.com/journal/ijerph
objective sleep quality.
To sum up, the effects
The relationships of of temperature
subjective appetite onand
appetite were mainly
temperature are shown reflected
in Tablein 6.subjective
Subjects’ appetite appetite at
lunch,
forand there
lunch waswas no significant
significantly effect
affected by on breakfast and
temperature. The supper.
desire to eat, hunger, and prospective
◦ C were significantly lower than those at 32 ◦ C. Fullness at 38 ◦ C was significantly
consumption at 36Table 5. The objective appetite in the four temperature conditions.
lower than that at 32 ◦ C, and fullness at 32 ◦ C was significantly higher than that at 28 ◦ C. Food
Index at 38 ◦ C andMeal
greasiness Objective
36 ◦ C was lower than that at 32 ◦ C, and Appetite
food greasiness at 32 ◦ C was higher than
that at 28 ◦ C. The fullness of supper at 28
38 ◦°C 32 °Clower than that36at°C
C was significantly 38 °C
32 ◦ C. This indicates
Meal
thatweight (g)
the subjective Breakfast
appetite 398.9
for lunch at 32 ◦
± 170.1
C was the389.8
best. ±This
160.5
result is447.2 ± 182.4
similar to that for389.8 ± 153.5
objective
sleep quality. Lunch 529.1 ± 178.6 614.6 ± 240.1 507.7 ± 225.1 568.2 ± 146.9
Supper 570.9 ± 321.2 567.8 ± 266.9 471.4 ± 159.9 530.7 ± 165.9
Meal time (min) Breakfast 9.4 ± 4.2 10.9 ± 2.9 11.6 ± 4.3 8.5 ± 4.2
Lunch 13.3 ± 8.2 19.8 ± 7.9 10.6 ± 3.9 16.9 ± 3.9
Supper 12.6 ± 3.2 14.9 ± 6.8 15.7 ± 5.4 14.1 ± 5.5Int. J. Environ. Res. Public Health 2019, 16, 270 10 of 13
Table 6. The subjective appetite in the four temperature conditions.
Subjective Appetite
Index Meal ◦C
28 32 ◦ C 36 ◦ C 38 ◦ C
Article
Breakfast 4.0 ± 2.3 The Effects
4.4 ± 1.8 5.3 ± 2.1 Weather
of High-Temperature 4.8 ±on1.8
Human
Desire to eat Lunch 5.0 ± 1.6 Sleep5.5 Quality
± 0.9 and Appetite 3.7 ± 1.5 ◆ 4.8 ± 1.8
Supper 5.7 ± 1.2 Guozhong5.6 ± 1.3 6.1 ± 1.7
Zheng *, Ke Li and Yajing Wang
5.8 ± 1.8
School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003,
Article
China; like@ncepu.edu.cn (K.L.); wangyajing@ncepu.edu.cn (Y.W.)
Breakfast 4.7 ± 2.6 The 4.4 ±zhengguozhong@ncepu.edu.cn;
Effects
* Correspondence: 0.9 5.3 ±Tel.:1.9
of High-Temperature 4.4 ±on1.2
Weather
+86-312-752-2443 Human
Hunger Lunch 4.8 ± 1.8 Sleep 5.4Quality
Received: 14 December 2018;and
± 1.2 Accepted:Appetite
3.2 ± 1.8 ◆ date 5.1 ± 2.1
16 January 2019; Published:
Supper 5.6 ± 1.1 Guozhong 5.4 ± 1.6 Yajing appears
Abstract: High-temperature
Zheng *, Ke Li andweather
6.0 ± 1.4 6.2 ± 1.5
Wang in high frequency, big strength, and long duration in
the summer. It is therefore important to study the effects of high-temperature weather on sleep
School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003,
Article
qualitylike@ncepu.edu.cn
China; and appetite. Ten
(K.L.);healthy college students(Y.W.)
wangyajing@ncepu.edu.cn were selected as subjects. The experiment
Breakfast 4.2 ± 2.6 The 4.4were±divided
Effects
conditions
* Correspondence: 1.1 by the daily 5.6
of High-Temperaturemaximum
zhengguozhong@ncepu.edu.cn; ±Tel.:temperature
2.4 Weather
+86-312-752-2443 °C, 32±
into 284.7 on1.6
°C, 36 Human
°C, and 38 °C.
Prospective consumption Lunch 5.9Quality
Received: 14
sleep quality
December 2018;and
±measured
was 1.3 Accepted: Appetite
3.7 ± 1.8 ◆
The objective sleep quality was measured by an intelligent sleep monitoring belt, and the subjective
5.5 ± 2.1 Sleep 16 January 2019; Published:
by a questionnaire survey. The
date
subjective5.4 ±
appetites 2.3
were assessed by a
visual analog scale (VAS), and the objective appetites were assessed by the meal weight and the meal
Supper 5.9 ± 1.4 Guozhong 5.4sleep± 1.4
Abstract: High-temperature
time. For
Zheng *, Ke Li andweather
quality, 5.6
Yajing appears
± 1.4 6.2 ±
at 321.6
Wang in high frequency, big strength, and long duration in
the objective results indicated that the sleep quality °C was the best,
the summer. It is therefore important to study the effects of high-temperature weather on sleep
School of Energy,
followed Power
by 28 °C, andthe
while Mechanical
sleep Engineering,
quality
Article North
at 36 °C andChina
38 °CElectric
was the Power University,
worst. Baoding
Significant 071003,
effects were
quality and appetite. Ten healthy
China; like@ncepu.edu.cn college students(Y.W.)
were selected as subjects. The experiment
reflected in sleep(K.L.); wangyajing@ncepu.edu.cn
Breakfast 5.0 ± 1.6 mainly
conditions
*had 4.6 ± 1.7
were divided
Correspondence:
duration
by the daily maximum
zhengguozhong@ncepu.edu.cn;
significant effects
4.6 ± 2.1
and shallow sleep. The
The Effects
on sleep calmness, difficulty
temperature
Tel.: 5.0 ± 1.9 Weather on Human
subjective results showed that temperature
of High-Temperature
into 28 °C, 32 °C, 36 °C, and 38 °C.
+86-312-752-2443
in falling asleep, sleep satisfaction, and sleep
The objective sleep quality wasArticle
5.1 ± 1.6 ◆ Weather on Human
measured by an intelligent sleep monitoring belt, and the subjective
Fullness Lunch 5.3 ± 1.7 adequateness.
Received: 14 December
6.8 ± 1.9 N
For appetite, the VAS
2018; Accepted: Sleep Quality
5.7 of and
± 0.8 Appetite
results 2019;
16 January
The Effects indicated
Published:
High-Temperature
sleep quality was measured by a questionnaire survey. The subjective appetites were assessed by a
thatdate high temperatures mainly led to a
reduction of appetite at lunch time. The meal weights of lunch were larger than those of supper
5.6 ± 1.8 ◆
visual analog scale (VAS), and the objective appetites were assessed by the meal weight and the meal
Supper 5.5 ± 1.4 Abstract:
6.9 ± 1.8
High-temperature weather
Guozhong Sleep6.4
except for 28 °C, and the meal time of lunch and supper was longer Quality
± 1.4 and Appetite
appearsZheng in high
*, Ke frequency,
Li
time. For sleep quality, the objective results indicated that the sleep quality at 32 °C was the best,
and Yajing bigthan
strength,
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the
timesummer.
of lunch was It is longer
therefore thanimportant
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36 °C. of
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paper can provide weather
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method
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quality at 36 Power
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of human selected as
andwangyajing@ncepu.edu.cn
Yajing Wang
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weather. experiment
mainly reflected in sleep duration China;and shallow sleep. The (K.L.);
subjective results showed that (Y.W.)
temperature
Breakfast 2.5 ± 2.5 The Effects
3.9 ± 1.6
The
Keywords:
4.9 ± 2.1
of High-Temperature
The Effects
objective
4.8 ±on2.7
of High-Temperature
Weather
conditions were divided by the* daily
had significant effects on sleepSchool Human
Weather on Human
sleep quality wasweather;
high-temperature
calmness,
measured
maximum zhengguozhong@ncepu.edu.cn;
Correspondence:
of Energy,
sleep
difficulty
by quality;
temperature into 28 °C, 32 °C,
Power in
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sleep satisfaction,
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36+86-312-752-2443
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sleepPower University, Baoding 071003,
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the core body temperature [13]. Moreover, due to the little adjustment of quilt and pajamas in summer,
quality and appetite are adversely affected by high temperatures [5–7]. Furthermore, insufficient sleep
may lead to frequent accidental injuries and huge economic losses [1], and the decreased appetite may
SWS is closely related to high temperatures, and it mainly influences the first half step of sleep before
cause weight loss or malnutrition, thus finally affecting health [8]. Therefore, to ensure physiological
midnight [34]. To sum up, body temperature regulation would affect sleep quality, and due to the
Int. J. Environ. Res. Public Health 2019, 16, x; doi: www.mdpi.com/journal/ijerph
decrease of nocturnal fall in body temperature, the minimum of rectal temperature increases, and the
heat loss of peripheral skin is reduced, and finally, wakefulness increases and the SWS decreases.
In this study, subjective questionnaires showed that at 36 ◦ C and 38 ◦ C, it was difficult to fall
asleep, and both sleep satisfaction and sufficiency were low, which indicates that high temperatures
led to poor sleep quality. Combined with the objective parameters of sleep quality, it was further found
that sleep quality at 32 ◦ C was better than that at 28 ◦ C. The reason is that at a lower temperature,
the activity of thermoregulation nerve center increased, resulting in the increase of stress hormone
secretion and wakefulness [24,36].You can also read
